To the top of the document
Captiva
To Previous Page To Next Page
GMDE Start Page Load static TOC Load dynamic TOC Help?

Fuel System Diagnosis

Circuit Description

The fuel pump is an in-tank type mounted to a fuel sender assembly. The fuel pump will remain on as long as the engine is cranking or running and the Engine Control Module (ECM) is receiving reference pulses from the crankshaft position (CKP) sensor. If there are no reference pulses, the ECM will turn off the fuel pump two seconds after the ignition switch is turned ON or two seconds after the engine stops running. The fuel pump delivers fuel to the fuel rail and the fuel injectors, where the fuel system pressure is controlled from 401 to 418 kPa (58 to 61 psi) by the fuel pump assembly. The excess fuel is returned to the fuel tank.

Caution : The fuel system is under pressure. To avoid fuel spillage and the risk of personal injury or fire, it is necessary to relieve the fuel system pressure before disconnecting the fuel lines.

Caution : Do not pinch or restrict nylon fuel lines to avoid damage that could cause a fuel leak, resulting in possible fire or personal injury.

Fuel Pressure Relief Procedure

  1. Remove the fuel cap.
  2. Remove the fuel pump fuse Ef16 from the engine fuse box.
  3. Start the engine and allow the engine to stall.
  4. Crank the engine for an additional 10 seconds.

Fuel System Diagnosis

Step Action Value(s) Yes No
1
  1. Relieve the fuel system pressure.
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel pressure within the values specified but not holding steady?
401~418 kPa (58~61 psi)
Go to Step 2
Go to Step 9
2
Inspect the fuel lines for a leak.
Is the problem found?
-
Go to Step 3
Go to Step 4
3
  1. Replace the fuel line(s) as needed.
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel pressure within the values specified but not holding steady?
401~418 kPa (58~61 psi)
System OK
-
4
  1. Remove the fuel pump assembly.
  2. With the fuel pump under pressure, inspect the fuel pump coupling hoses for leaking.
Is the problem found?
-
Go to Step 5
Go to Step 6
5
  1. Tighten or replace the fuel pump coupling hoses as needed.
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel pressure within the values specified but not holding steady?
401~418 kPa (58~61 psi)
System OK
-
6
  1. Replace the fuel pump assembly.
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel pressure within the values specified but not holding steady?
401~418 kPa (58~61 psi)
System OK
-
7
  1. Remove the fuel rail and the fuel injectors as an assembly.
  2. With the fuel system under pressure, inspect all of the fuel injectors for leaking.
Is the problem found?
-
Go to Step 8
-
8
  1. Replace the leaking fuel injector(s).
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel pressure within the values specified but not holding steady?
401~418 kPa (58~61 psi)
System OK
-
9
  1. Relieve the fuel system pressure.
  2. Install a fuel pressure gauge.
  3. Turn the ignition ON.
Is the fuel system pressure below the values specified and holding steady?
401~418 kPa (58~61 psi)
Go to Step 6
Go to Step 10
10
Inspect the fuel lines for leaks.
Is the problem found?
-
Go to Step 3
Go to Step 11
11
  1. Remove the fuel pump assembly.
  2. With the fuel pump under pressure, inspect the fuel pump coupling hoses for leaking.
Is the problem found?
-
Go to Step 5
Go to Step 12
12
  1. Remove the fuel rail and the fuel injectors as an assembly.
  2. With the fuel system under pressure, inspect all of the fuel injectors for leaking.
Is the problem found?
-
Go to Step 8
Go to Step 6

Fuel Pump Relay Circuit Check

Circuit Description

When the ignition switch is turned ON, the Engine Control Module (ECM) will supply battery voltage to activate the fuel pump relay and run the in-tank fuel pump. The fuel pump will operate as long as the engine is cranking or running and the ECM is receiving ignition reference pulses.
If there are no reference pulses, the ECM will shut off the fuel pump within 2 seconds after the ignition switch is turned ON.

Diagnostic Aids

An intermittent problem may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation.

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. This step checks for the ECM providing a ground for the operation of the fuel pump relay.
  2. By confirming that the wiring is OK using Steps 2 through 6, it can be determined that the fuel pump relay is at fault.
  3. After determining that there is no ground being provided by the ECM to the fuel pump relay, the fault is either the ECM or the wiring between the ECM and the fuel pump relay.

Fuel Pump Relay Circuit Check

Step Action Value(s) Yes No
1
  1. Turn the ignition OFF for 10 seconds.
  2. Turn the ignition ON.
  3. Listen for in-tank fuel pump operation.
Does the fuel pump operate for the time specified?
2 sec
System OK
Go to Step 2
2
  1. Turn the ignition OFF.
  2. Disconnect the fuel pump relay.
  3. Connect a test light between the fuel pump relay connector terminal 30 and ground.
Turn the ignition ON. Is the test light on?
-
Go to Step 3
Go to Step 8
3
  1. Turn the ignition OFF.
  2. Connect a test light between the fuel pump relay connector terminal 85 and battery positive.
  3. Turn the ignition ON.
  4. With the ignition ON, the test light should light for the time specified.
Is the test light on?
2 sec
Go to Step 4
Go to Step 9
4
  1. Turn the ignition OFF.
  2. Connect a test light between the fuel pump relay connector terminal 30 and ground.
Is the test light on?
-
Go to Step 5
Go to Step 11
5
Check for an open or short to ground in the wire between the fuel pump relay connector terminal 87 and the fuel pump connector terminal 4.
Is the problem found?
-
Go to Step 6
Go to Step 7
6
  1. Repair the wire between the fuel pump relay connector terminal 87 and the fuel pump connector terminal 3.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-
7
  1. Replace the fuel pump relay.
  2. Turn the ignition OFF for 10 seconds.
  3. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-
8
Check for an open wire between the fuel pump relay connector terminal 30 and the battery.
Is the problem found?
-
Go to Step 13
-
9
Check for an open wire between the fuel pump relay connector terminal 85 to the engine control module (ECM) connector J1 terminal 51.
Is the problem found.
-
Go to Step 10
Go to Step 12
10
  1. Repair the wire between the fuel pump relay connector terminal 85 to the ECM connector J1 terminal 51.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-
11
  1. Replace the fuse Ef16 or repair the wire between the fuel pump relay connector terminal 30 and the battery.
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-
12
  1. Turn the ignition OFF.
  2. Replace the ECM.
  3. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-
13
  1. Replace the fuse Ef16 or repair the wire between the fuel pump relay connector terminal 30 and the ignition system
  2. Install the fuel pump relay.
  3. Turn the ignition OFF for 10 seconds.
  4. Turn the ignition ON.
Does the fuel pump operate for the time specified?
2 sec
System OK
-

Main Relay Circuit Check

Circuit Description

When the ignition is turned ON or to the START position, the main relay is energized. The main relay then supplies voltage to the engine fuse box fuse Ef12 and the engine fuse box fuse Ef15.

Diagnostic Aids

Main Relay Circuit Check

Step Action Value(s) Yes No
1
  1. Turn the ignition OFF.
  2. Disconnect the engine fuse block fuses Ef12 and Ef15.
  3. Turn the ignition ON.
  4. With a test light connected to ground, probe the fuse terminals nearest the main relay for fuses Ef12 and Ef15.
Is the test light on at both terminals?
-
System OK
Go to Step 2
2
Check the test light.
Is the test light on at only one terminal?
-
Go to Step 9
Go to Step 3
3
Check the test light.
Is the test light off at both terminals?
-
Go to Step 4
-
4
  1. Turn the ignition OFF.
  2. Inspect the engine fuse block fuse Ef13.
Is the fuse OK?
-
Go to Step 5
Go to Step 10
5
  1. Disconnect the main relay.
  2. Connect a test light between the main relay connector terminal 85 and ground.
Is the test light on?
-
Go to Step 6
Go to Step 11
6
Connect a test light between the main relay connector terminal 86 and battery voltage.
Is the test light on?
-
Go to Step 7
Go to Step 12
7
Connect a test light between the main relay connector terminal 30 and ground.
Is the test light on?
-
Go to Step 8
Go to Step 13
8
Check for an open in the wiring between the main relay connector terminal 87 and the engine fuse block terminals for fuses Ef12 and Ef15.
Is the problem found?
-
Go to Step 9
Go to Step 14
9
Repair the open in the wiring between the main relay connector terminal 87 and the engine fuse block terminal(s) for fuses Ef12 and Ef15.
Is the repair complete?
-
System OK
-
10
Replace the engine fuse block fuse Ef13.
Is the repair complete?
-
System OK
-
11
Repair the open in the wiring between the main relay connector terminal 85 and the ignition switch.
Is the repair complete?
-
System OK
-
12
Repair the open in the wiring between the main relay connector terminal 86 and ground.
Is the repair complete?
-
System OK
-
13
Repair the open in the wiring between the main relay connector terminal 30 and the battery.
Is the repair complete?
-
System OK
-
14
Replace the main relay.
Is the repair complete?
-
System OK
-

Manifold Absolute Pressure Check

Circuit Description

The Manifold Absolute Pressure (MAP) sensor measures the changes in the intake manifold pressure which result from engine load (intake manifold vacuum) and rpm changes. The MAP sensor converts these changes into a voltage output. The engine control module (ECM) sends a 5-volt reference voltage to the MAP sensor. As the intake manifold pressure changes, the output voltage of the MAP sensor also changes. A low voltage (high vacuum) output of 1 to 2 volts is present at idle. A high voltage (low vacuum) output of 4.0 to 4.8 volts is present at wide open throttle. The MAP sensor is also used under certain conditions to measure baro-metric pressure. This allows the ECM to make adjustments for altitude changes. The ECM uses the MAP sensor for fuel delivery and ignition timing changes.

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. Applying 34 kPa (10 inches Hg) of vacuum to the MAP sensor should cause the voltage to change. Subtract the second voltage reading from the first. That voltage value should be more than 1.5 volts. When applying vacuum to the MAP sensor, the change in the voltage should happen instantly. A slow voltage change indicates a faulty MAP sensor.
  2. Disconnect the MAP sensor from the bracket and twist the MAP sensor. Output changes more than 0.1 volt indicate a faulty connector or connection.

Manifold Absolute Pressure Check

Step Action Value(s) Yes No
1
  1. Turn the ignition OFF.
  2. Connect a scan tool to the Data Link Connector (DLC).
  3. Turn the ignition ON.
  4. Compare the Manifold Absolute Pressure (MAP) sensor voltage reading from the scanner with that from a known good vehicle.
Is the difference in the two voltage readings less than the value specified?
0.4 v
Go to Step 2
Go to Step 5
2
  1. Turn the ignition OFF.
  2. Connect a scan tool to the DLC.
  3. Disconnect the MAP sensor vacuum line.
  4. Connect a hand vacuum pump to the MAP sensor.
  5. Turn the ignition ON.
  6. Note the MAP sensor voltage.
  7. Apply 10 in. Hg (34 kPa) of vacuum to the MAP sensor and note the voltage change.
Is the difference in voltage readings more than the value specified?
1.5 v
System OK
Go to Step 3
3
Inspect the MAP sensor connector terminals.
Is the problem found?
-
Go to Step 4
Go to Step 5
4
Repair the MAP sensor connector terminals as needed.
Is the repair complete?
-
System OK
-
5
Replace the MAP sensor.
Is the repair complete?
-
System OK
-

Ignition System Check

Circuit Description

The Electronic Ignition (EI) system uses a waste spark method of spark distribution. In this type of EI system, the Crankshaft Position (CKP) sensor is mounted to the oil pump near a slotted wheel that is a part of the crankshaft pulley. The CKP sensor sends reference pulses to the engine control module (ECM). The ECM then triggers the EI system ignition coil. Once the ECM triggers the EI system ignition coil, both of the connected spark plugs fire at the same time. One cylinder is on its compression stroke at the same time that the other is on the exhaust stroke, resulting in lower energy needed to fire the spark plug in the cylinder on its exhaust stroke.
This leaves the remainder of the high voltage to be used to fire the spark plug in the cylinder on its compression stroke. Since the CKP sensor is in a fixed position, timing adjustments are not possible or needed.

Test Description

The number(s) below refer to step(s) on the diagnostic table.
  1. It is important to check for the presence of spark to all of the cylinders to isolate the problem to either EI system ignition coil inputs or outputs.
  2. In checking the ECM outputs for the electronic spark timing signal, it recommended to use an oscilloscope to view the varying voltage signals. In measuring these outputs with a voltmeter, intermittent errors may occur that cannot be seen by a voltmeter.
  3. After confirming ECM inputs for the electronic spark timing to the EI system ignition coil are OK, it can be determined that a faulty EI system ignition coil is at fault.
  4. After confirming proper CKP sensor inputs to the ECM and no wiring problems present, it can be determined that the ECM is at fault.
  5. This step, along with step 25, checks for battery voltage and a ground to the EI system ignition coil.

Ignition System Check

Caution : Use only electrically insulated pliers when handling ignition wires with the engine running to prevent an electrical shock.

Step Action Value(s) Yes No
1
  1. Remove the spark plugs.
  2. Inspect for wet spark plugs, cracks, wear, improper gap, burned electrodes, or heavy deposits.
  3. Replace the spark plugs as needed.
Is the repair complete?
-
System OK
Go to Step 2
2
Check for the presence of spark from all of the ignition wires while cranking the engine.
Is spark present from all of the ignition wires?
-
System OK
Go to Step 3
3
  1. Measure the resistance of the ignition wires.
  2. Replace any ignition wire(s) with a resistance above the value specified.
  3. Check for the presence of spark from all of the ignition wires.
Is spark present from all of the ignition wires?
30,000 Ω
System OK
Go to Step 4
4
Is spark present from at least one of the ignition wires, but not all of the ignition wires?
-
Go to Step 5
Go to Step 12
5
  1. Turn the ignition OFF.
  2. Disconnect the Electronic Ignition (EI) system ignition coil connector.
  3. While cranking the engine, measure the voltage at the EI system ignition coil connector terminal 3.
Does the voltage fluctuate within the values specified?
0.2-2.0 v
Go to Step 6
Go to Step 7
6
While cranking the engine, measure the voltage at the EI system ignition coil connector terminal 1.
Does the voltage fluctuate within the values specified?
0.2-2.0 v
Go to Step 10
Go to Step 8
7
Check for an open in the wire from the EI system ignition coil connector terminal 3 to the engine control module (ECM) connector J2 terminal 35.
Is the problem found?
-
Go to Step 9
Go to Step 11
8
Check for an open in the wire from the EI system ignition coil connector terminal 1 to the ECM connector J2 terminal 40.
Is the problem found?
-
Go to Step 9
Go to Step 11
9
  1. Repair the wiring as needed.
  2. Connect the EI system ignition coil connector.
  3. Check for the presence of spark from all of the ignition wires.
Is spark present from all of the ignition wires?
-
System OK
-
10
  1. Turn the ignition OFF.
  2. Replace the electronic ignition system ignition coil.
  3. Connect the EI system ignition coil connector.
  4. Check for the presence of spark from all of the ignition wires.
Is spark present from all of the ignition wires?
-
System OK
-
11
  1. Turn the ignition OFF.
  2. Replace the ECM.
  3. Connect the EI system ignition coil connector.
  4. Check for the presence of spark from all of the ignition wires.
Is spark present from all of the ignition wires?
-
System OK
-
12
  1. Turn the ignition OFF.
  2. Disconnect the Crankshaft Position (CKP) sensor connector.
  3. Measure the resistance between the CKP sensor terminals 1 and 2.
Is the resistance within the value specified?
400-600 Ω
Go to Step 13
Go to Step 28
13
  1. Measure the resistance between the CKP sensor terminals 1 and 3.
  2. Measure the resistance between the CKP sensor terminals 2 and 3.
  3. Is the resistance infinite (open circuit)?
Is the repair complete?
-
Go to Step 14
Go to Step 28
14
  1. Turn the ignition ON.
  2. Measure the voltage between the CKP sensor connector terminals 1 and 3.
Is the voltage within the value specified?
1.3-1.5 v (2.4-2.7 v)*
Go to Step 20
Go to Step 15
15
Measure the voltage between the CKP sensor connector terminal 1 and ground.
Is the voltage within the value specified?
1.3-1.5 v (2.4-2.7 v)*
Go to Step 17
Go to Step 16
16
Check the wire between the CKP sensor connector terminal 1 and the ECM connector J2 terminal 14 for an open or short.
Is the problem found?
 -
Go to Step 18
Go to Step 11
17
Check the wire between the CKP sensor connector terminal 3 and ground for an open or short.
Is the problem found?
-
Go to Step 19
Go to Step 11
18
Repair the wire between the CKP sensor connector terminal 1 and the ECM connector J2 terminal 14.
Is the repair complete?
-
System OK
-
19
Repair the wire between the CKP sensor connector terminal 3 and ground.
Is the repair complete?
-
System OK
-
20
  1. Turn the ignition ON.
  2. Measure the voltage between the CKP sensor connector terminals 2 and 3.
Is the voltage within the value specified?
1.3-1.5 v (2.4-2.7 v)*
Go to Step 24
Go to Step 21
21
Measure the voltage between the CKP sensor connector terminal 2 and ground.
Is the voltage within the value specified?
1.3-1.5 v (2.4-2.7 v)*
Go to Step 17
Go to Step 22
22
Check the wire between the CKP sensor connector terminal 2 and the ECM connector J2 terminal 15 for an open or short.
Is the problem found?
-
Go to Step 23
Go to Step 11
23
Repair the wire between the CKP sensor connector terminal 2 and the ECM connector J2 terminal 15.
Is the repair complete?
-
System OK
-
24
  1. Turn the ignition OFF.
  2. Connect a test light between the EI system ignition coil connector terminal 2 and ground.
  3. Turn the ignition ON.
Is the test light on?
-
Go to Step 25
Go to Step 26
25
Connect a test light between the EI system ignition coil connector terminal 2 and battery positive.
Is the test light on?
-
Go to Step 5
Go to Step 27
26
Check for an open or short to ground in the wiring between the EI system ignition coil connector, terminal 2 and the ignition switch.
Is the problem found?
-
Go to Step 29
-
27
Repair the wire between the EI system ignition coil connector terminal 3 and ground.
Is the repair complete?
-
System OK
-
28
  1. Turn the ignition OFF.
  2. Replace the CKP sensor.
Is the repair complete?
-
System OK
-
29
Replace the fuse F27 or repair the open in the wiring between the EI system ignition coil connector terminal 2 and the ignition switch.
Is the repair complete?
-
System OK
-

Engine Cooling Fan Circuit Check

Circuit Description

The engine cooling fan circuit operates the main cooling fan and the auxiliary cooling fan. The cooling fans are controlled by the Engine Control Module (ECM) based on inputs from the Engine Coolant Temperature (ECT) sensor and the Air Conditioning Pressure (ACP) sensor. The ECM controls the low speed cooling fan operation by internally grounding the ECM connector J1 terminal 43. This energizes the low speed cooling fan relay and operates the main cooling fan at low speed as the cooling fans. The ECM controls the high speed cooling fan operation by internally grounding the ECM connector J1 terminal 24. This energizes the high speed cooling fan relay resulting in high speed fan operation as the cooling fans are now connected in a parallel circuit.

Diagnostic Aids

Engine Cooling Fan Circuit Check

Step Action Value(s) Yes No
1
Perform the Diagnostic system check.
Was the check performed?
-
Go to Step 2
Go to "Diagnostic System Check"
2
  1. Check the fuses Ef8 and Ef9 in engine fuse block.
  2. Replace the fuse(s) as needed.
Is the fuse(s) OK?
-
Go to Step 3
Go to "Diagnostic Aids"
3
  1. Turn the ignition switch to LOCK.
  2. Turn the A/C switch OFF, if equipped.
  3. Install the scan tool to the Data Link Connector (DLC).
  4. Start the engine.
  5. The main cooling fan should run at low speed when the coolant temperature reaches 97°C (207°F).
Does the cooling fan run at low speed?
-
Go to Step 4
Go to Step 8
4
The cooling fans should run at high speed when the coolant temperature reaches 101°C (214°F).
Do the cooling fans run at high speed?
-
Go to Step 5
Go to Step 19
5
  1. Turn the ignition switch to LOCK.
  2. Start the engine.
  3. Turn the A/C switch ON.
Does the cooling fan runs at low speed?
-
Go to Step 7
Go to Step 6
6
  1. Diagnose the A/C compressor clutch circuit.
  2. Repair the A/C compressor clutch circuit as needed.
Is the repair complete?
-
System OK
-
7
  1. Turn the ignition switch to LOCK.
  2. Connect the A/C pressure gauge.
  3. Start the engine.
  4. Turn the A/C switch ON and raise the rpm.
  5. The cooling fan should run at high speed when the high side A/C pressure reaches 1,859 kPa (269 psi).
Do the cooling fans run at high speed?
-
System OK
-
8
  1. Turn the ignition switch to LOCK.
  2. Disconnect the main cooling fan connector.
  3. Turn the ignition switch to ON.
  4. Connect a test light between the main cooling fan connector terminal 2 and ground.
Is the test light illuminate?
-
Go to Step 9
Go to Step 12
9
Connect a test light between terminal the main cooling fan connector terminal 1 and battery positive terminal.
Is the test light illuminate?
-
Go to Step 11
Go to Step 10
10
Repair open circuit between the main cooling fan connector terminal 1 and ground.
Is the repair complete?
-
System OK
-
11
Check for a damaged terminals in main cooling fan connector and repair it or replace the main cooling fan.
Is the repair complete?
-
System OK
-
12
  1. Turn the ignition switch to ON.
  2. Connect a test light between the low speed cooling fan relay connector terminal 30 and 85 and ground.
Does the test light on for both case?
-
Go to Step 14
Go to Step 13
13
Repair power supply circuit.
  • Fuse Ef28 and the low speed cooling fan relay connector terminal 85.
  • Fuse Ef8 and the low speed cooling fan relay connector terminal 30.
Is the repair complete?
-
System OK
Go to Step 14
14
  1. Turn the ignition switch to LOCK.
  2. Disconnect Engine Control Module (ECM) connectors.
  3. Turn the ignition switch to ON.
  4. Connect a jump wire between the ECM connector J1 terminal 43 and ground.
Does the cooling fan run at low speed?
-
Go to Step 15
Go to Step 16
15
Replace the ECM.
Is the replacement complete?
-
System OK
-
16
  1. Turn the ignition switch to LOCK.
  2. Measure the resistance between following terminals:
    • The low speed cooling fan relay terminal 86 and ECM connector J1 terminal 43.
    • The low speed cooling fan relay terminal 87 and the auxiliary cooling fan terminal 2.
Are the resistance the specified value?
0 Ω
Go to Step 18
Go to Step 17
17
Repair open circuit.
Is the repair complete?
-
System OK
-
18
Replace the low speed cooling fan relay.
Is the replacement complete?
-
System OK
-
19
  1. Turn the ignition switch to LOCK.
  2. Disconnect the auxiliary cooling fan connector.
  3. Turn the ignition switch to ON.
  4. Connect a test light between the auxiliary cooling fan connector terminal 2 and ground.
Is the test light illuminate?
-
Go to Step 20
Go to Step 24
20
Connect a test light between the auxiliary cooling fan connector terminal 1 and battery positive terminal.
Is the test light illuminate?
-
Go to Step 21
Go to Step 23
21
Replace the auxiliary cooling fan.
Is the replacement complete?
-
System OK
Go to Step 22
22
Repair an open circuit between following terminals:
  • The main cooling fan connector terminal 2 and the high speed cooling fan relay connector terminal 87.
  • The main cooling fan connector terminal and ground.
Is the repair complete?
-
System OK
Go to Step 11
23
Repair an open circuit between the auxiliary cooling fan connector terminal 1 and ground.
Is the repair complete?
-
System OK
-
24
  1. Turn the ignition switch to ON.
  2. Connect a test light between the high speed cooling fan relay connector terminal and ground.
Does the test light illuminate for both case?
-
Go to Step 26
Go to Step 25
25
Repair open power supply circuit:
  • Fuse Ef9 and the high speed cooling fan relay connector terminal 86.
  • Fuse Ef9 and the high speed cooling fan relay connector terminal 30.
Is the repair complete?
-
System OK
Go to Step 26
26
  1. Turn the ignition switch to LOCK.
  2. Disconnect Engine Control Module (ECM) connectors.
  3. Turn the ignition switch to ON.
  4. Connect a jump wire between connector J1 terminal 24 and ground.
Does the cooling fans run at high speed?
-
Go to Step 15
Go to Step 27
27
  1. Turn the ignition switch to LOCK.
  2. Measure the resistance between following terminals:
    • The high speed cooling fan relay connector terminal 86 and the ECM connector J1 terminal 24.
    • The high speed cooling fan relay connector terminal 87 and the main cooling fan connector terminal 2.
Are the resistance the specified value?
0 Ω
Go to Step 29
Go to Step 28
28
Repair open circuit between specific circuit wiring.
Is the repair complete?
-
System OK
-
29
Replace the high speed cooling fan relay.
Is the replacement complete?
-
System OK
Go to Step 15

Data Link Connector Diagnosis

Circuit Description

The provision for communicating with the Engine Control Module (ECM) is the Data Link Connector (DLC). It is located under the instrument panel. The DLC is used to connect the scan tool. Battery power and ground is supplied for the scan tool through the DLC. The serial data circuit to the DLC allows the ECM to communicate with the scan tool.

Diagnostic Aids

Ensure that the correct application (model line, car year, etc.) has been selected on the scan tool. If communication still cannot be established, try the scan tool on another vehicle to ensure that the scan tool or cables are not the cause of the condition.
An intermittent may be caused by a poor connection, rubbed through wire insulation, or a broken wire inside the insulation.
Any circuitry that is suspected of causing an intermittent complaint should be thoroughly checked for the following conditions:

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.
  1. The Diagnostic System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
  2. Locate and repair any shorts that may have caused the fuse to open before replacement, if the no voltage condition was due to an open fuse.
  3. The scan tool or associated cables could be malfunctioning. Refer to the scan tool's manual for repair information.

Data Link Connector Diagnosis

Step Action Value(s) Yes No
1
Perform the Diagnostic system check.
Was the check performed?
-
Go to Step 2
Go to "Diagnostic System Check"
2
With a test light connected to the ground, probe the Data Link Connector (DLC) battery feed terminal 16.
Is the test light illuminate?
-
Go to Step 4
Go to Step 3
3
Repair an open or short to ground in the DLC battery feed circuit .
Is the repair complete?
-
Go to Step 4
-
4
With a test light connected to the battery, probe the DLC ground terminal 4 and 5.
Is the test light illuminate?
-
Go to Step 6
Go to Step 5
5
Repair an open circuit.
Is the repair complete?
-
Go to Step 6
-
6
  1. Turn the ignition switch to LOCK.
  2. Install the scan tool to the DLC.
  3. Turn the ignition switch to ON.
Does the scan tool power up?
-
Go to Step 8
Go to Step 7
7
Check for damages in the terminal of DLC and scan tool, and repair as needed.
Is the repair complete?
-
Go to Step 8
-
8
Using a scan tool, request engine data of Engine Control Module (ECM).
Does the scan tool display any data?
-
Go to Step 12
Go to Step 9
9
Install the scan tool on another vehicle and check for proper operation.
Does the scan tool work properly on a different vehicle.
-
Go to Step 11
Go to Step 10
10
The scan tool is malfunctioning.
Refer to the scan tool's manual for repair.
Is the repair complete?
-
Go to Step 12
-
11
Repair communication circuit between ECM and DLC.
Is the repair complete?
-
Go to Step 12
-
12
  1. Using a scan tool, clear the Diagnostic Trouble Codes(DTCs).
  2. Attempt to start the engine.
Does the engine and continue to run?
-
Go to Step 13
Go to Step 2
13
  1. Allow the engine to idle until normal operation temperature reached.
  2. Check if any DTCs are set?
Are any DTCs displayed that have not been diagnosed?
-
Go to "Applicable DTC Table"
System OK

Fuel Injector Balance Test

A fuel injector tester is used to energize the injector for a precise amount of time, thus spraying a measured amount of fuel into the intake manifold. This causes a drop in the fuel rail pressure that can be recorded and used to compare each of the fuel injectors. All of the fuel injectors should have the same pressure drop.

Fuel Injector Balance Test Example

Cylinder
1
2
3
4
First Reading
296 kPa (43 psi)
296 kPa (43 psi)
296 kPa (43 psi)
296 kPa (43 psi)
Second Reading
131 kPa (19 psi)
117 kPa (17 psi)
124 kPa (18 psi)
145 kPa (21 psi)
Amount Of Drop
165 kPa (24 psi)
179 kPa (26 psi)
172 kPa (25 psi)
151 kPa (22 psi)
Average Range: 156~176 kPa (22.5~25.5 psi)
Injector OK
Faulty Injector - Too Much Pressure Drop
Injector OK
Faulty Injector - Too Little Pressure Drop

Caution : The fuel system is under pressure. To avoid fuel spillage and the risk of personal injury or fire, it is necessary to relieve the fuel system pressure before disconnecting the fuel lines.

Caution : Do not pinch or restrict nylon fuel lines. Damage to the lines could cause a fuel leak, resulting in possible fire or personal injury.

Notice : In order to prevent flooding of the engine, do not perform the Injector Balance Test more than once (including any retest on faulty fuel injectors) without running the engine.

Test

  1. Turn the ignition switch to ON in order to get the fuel pressure to its maximum level.
  2. Allow the fuel pressure to stabilize and then record this initial pressure reading. Wait until there is no movement of the needle on the fuel pressure gauge.
  3. Follow the manufacturer's instructions for the use of the adapter harness. Energize the fuel injector tester once and note the fuel pressure drop at its lowest point. Record this second reading. Subtract it from the first reading to determine the amount of the fuel pressure drop.
  4. Disconnect the fuel injector tester from the fuel injector.
  5. After turning the ignition switch to ON, in order to obtain maximum pressure once again, make a connection at the next fuel injector. Energize the fuel injector tester and record the fuel pressure reading. Repeat this procedure for all the injectors.
  6. Retest any of the fuel injectors that the pressure drop exceeds the 10 kPa (1.5 psi) of the average pressure drop value.
  7. Replace any of the fuel injectors that fail the retest.
  8. If the pressure drop of all of the fuel injectors is within 10 kPa (1.5 psi) of the average pressure drop value, then the fuel injectors are flowing normally and no replacement should be necessary.
  9. Reconnect the fuel injector harness and review the symptom diagnostic tables.
  10. An engine cool down period of 10 minutes is necessary in order to avoid irregular readings due to hot soak fuel boiling.
  11. Connect the fuel pressure gauge carefully to avoid any fuel spillage.
  12. The fuel pump should run about 2 seconds after the ignition is turned to the ON position.
  13. Insert a clear tube attached to the vent valve of the fuel pressure gauge into a suitable container.
  14. Bleed the air from the fuel pressure gauge and hose until all of the air is bled from the fuel pressure gauge.
  15. The ignition switch must be in the OFF position at least 10 seconds in order to complete the Engine Control Module (ECM) shutdown cycle.


To Previous Page To Next Page
© Copyright Chevrolet Europe. All rights reserved