Cruze

DTC P0128

The engine control module (ECM) monitors the temperature of the engine coolant for engine control and as an enabling criteria for some diagnostics. The amount of air flow into an engine is proportional to the amount of heat an engine generates. The ECM monitors the amount of air flow into the engine to calculate engine coolant temperature (ECT). The ECM uses the calculated temperature to determine if the engine has warmed up to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach the thermostat regulating temperature, diagnostics that use the ECT as enabling criteria, may not run when expected. If the engine coolant temperature fails to reach the thermostat regulating temperature, before a predetermined amount of air flow enters the engine, the DTC sets.

The ECM detects that the amount of time it takes for the ECT sensor 1 to reach maximum temperature has exceeded a calibrated time.

DTC P0128 00 is a Type B DTC.

DTC P0128 00 is a Type B DTC.

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 OFF, inspect the cooling system surge tank for the proper coolant level. Refer to Loss of Coolant and Cooling System Draining and Filling .
2. Ignition ON, observe the DTC information with a scan tool. DTC P00B7 00, P0597 00, P0598 00, P0599 00, or P2181 00 should not be set.

⇒	If a DTC is set, refer to Diagnostic Trouble Code (DTC) List - Vehicle .

3. Engine idling for 15 min with the A/C OFF.

Note: Depending on ambient temperature, it may take up to 4 min for the temperatures to equalise.

4. Command the Engine Coolant Thermostat Heater to 0% with a scan tool. Increase the engine speed to 3 000 RPM. Observe the scan tool ECT Sensor 1 parameter. The temperature should increase to greater than 102°C (215°F).

⇒	If less than the specified value, replace the E41 Engine Coolant Thermostat Heater.

5. Command the E41 Engine Coolant Thermostat Heater to 100% with a scan tool. Increase the engine speed to 3 000 RPM. Observe the scan tool Radiator Coolant Temperature Sensor and the ECT Sensor 1 parameters. The Radiator Coolant Temperature Sensor and the ECT Sensor 1 parameters should be within 20°C (68°F).
6. Engine idling, observe the DTC information with a scan tool. DTC P0128 00 should not set.
7. Operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.

1. Ignition OFF, disconnect the harness connector at the B34 Engine Coolant Temperature Sensor.
2. Ignition OFF for 1 min, test for less than 5 Ω between the low reference circuit terminal 2 and ground.

⇒	If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.

3. Ignition ON, verify the scan tool ECT Sensor 1 parameter is colder than -39°C (-38°F).

⇒	If warmer than the specified range, test the signal circuit terminal 2 for a short to ground. If the circuit tests normal, replace the K20 Engine Control Module.

Note: If the fuse in the jumper wire opens, the signal circuit is shorted to a voltage and the sensor may be damaged.

4. Install a 3A fused jumper wire between the signal circuit terminal 2 and the low reference circuit terminal 1. Verify the scan tool ECT Sensor 1 parameter is greater than 130°C (266°F).

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

5. If all circuits test normal, test or replace the B34 Engine Coolant Temperature Sensor.

Static Test

1. Ignition off, disconnect the harness connector at the B34 Engine Coolant Temperature Sensor.

Note: A thermometer can be used to test the sensor off the vehicle.

2. Test the B34 Engine Coolant Temperature Sensor by varying the sensor temperature while monitoring the sensor resistance. Compare the readings with the Temperature Versus Resistance table and verify that the resistance is within 5% of the specification.

⇒	If not within the specified range, replace the B34 Engine Coolant Temperature Sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.