Captiva

DTC P159F or P15A0 - LNQ

The ECM supplies 5 V reference voltage, through the 5 V reference voltage circuit, to the fuel economy mode switch. The 5 V reference voltage causes current to flow through a series of resistors in the switch to the switch ground circuit. The ECM monitors the reference voltage through a discrete fuel economy mode switch signal circuit. When the switch button is momentarily pressed, the switch contacts allow the 5 V reference voltage to by-pass one of the resistors. The ECM detects the resulting voltage drop as a fuel economy mode request and sends a GMLAN message to the transmission control module (TCM) indicating the request. When the TCM receives the request, throttle progressions and transmission shift points are modified to optimize fuel efficiency. The instrument panel cluster also receives the fuel economy mode request message from the ECM and illuminates the fuel economy mode indicator lamp. The fuel economy mode switch must be pressed for between 0.094-1.5 s to activate the fuel economy mode. Voltage on the signal wire is normally between 1.45-3.45 V with the switch depressed. When the switch is released, voltage on the signal wire is normally between 3.65-4.45 V.

The ECM detects that the voltage on the fuel economy mode switch signal wire is either too low or too high out of range.

DTCs P159F and P15A0 are Type B DTCs

DTCs P159F and P15A0 are Type B DTCs

Schematic Reference

Engine Controls Schematics

Connector End View Reference

Component Connector End Views

Electrical Information Reference

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References for scan tool information

1. Ignition ON, observe the scan tool Fuel Economy Mode parameter. The parameter should display Inactive.
2. Ignition ON, command the Fuel Economy ON and OFF with a scan tool. The Fuel Economy Mode parameter should display Active and Inactive as commanded.
3. Operate the vehicle within the Conditions for Running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.

Note: You must perform the Circuit/System Verification before proceeding with Circuit/System Testing.

1. Ignition OFF, disconnect the X1 harness connector at the Fuel Economy Mode switch.
2. Test for less than 5 Ω between the ground circuit terminal 3 and ground.

⇒	If greater than the specified range, test the ground circuit for a open/high resistance and repair as necessary.

3. Ignition ON, test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground.

⇒	If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

⇒	If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

4. Observe the scan tool Fuel Economy Mode Switch parameter. The parameter should display Circuit Low Voltage.

⇒	If the parameter does not display the specified value, test the signal circuit for a short-circuit to voltage. If the circuit tests normal, replace the K20 Engine Control Module.

5. Connect a 3 A fused jumper wire between 5 V reference circuit terminal 1 and signal circuit terminal 2 of the harness connector. Verify the scan tool Fuel Economy Mode Switch parameter displays Circuit High Voltage.
6. If all scan tool parameter displays are normal, test or replace the S112 Fuel Economy Mode Switch.

Static Test

1. Disconnect the S112 Fuel Economy Mode Switch and measure between the 5 V reference voltage circuit terminal 1 of the switch and signal circuit terminal 2 of the switch for 266-294 Ω.

⇒	If not the specified range, replace the S112 Fuel Economy Mode Switch.

2. Measure between the 5 V reference voltage circuit terminal 1 and the ground circuit terminal 3 for 1 414-1 562 Ω. With the switch in open position.

⇒	If not the specified range, replace the S112 Fuel Economy Mode Switch.

3. Measure between the 5 V reference voltage circuit terminal 1 ground circuit terminal 3 for 486Ω538 Ω. With the switch in closed position.

⇒	If not the specified range, replace the S112 Fuel Economy Mode Switch.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.