Conditions for Clearing the MIL/DTC
- The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
- A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
- Clear the MIL and the DTC with a scan tool.
DTC P0128
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Engine Control Module (ECM) Connector End Views |
||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | - | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 |
IMPORTANT:
The cooling fans are commanded ON, if equipped, when certain engine coolant temperature (ECT) DTCs are set. Is the cooling system coolant low? |
- | Go to Draining and Filling Cooling System in Engine Cooling | Go to Step 3 |
| 3 | Test and verify the proper operation of the thermostat. Refer to Thermostat Diagnosis
in Engine Cooling. Did you find and correct the condition? |
- | Go to Step 14 | Go to Step 4 |
| 4 |
|
- | Go to Step 14 | Go to Step 5 |
| 5 | Test for an intermittent and for a poor connection at the engine control module (ECM). Refer to Testing for Intermittent Conditions and Poor Connections
, Repairing Connector Terminals
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 14 | Go to Step 6 |
| 6 | Measure the resistance of the ECT sensor signal circuit between the sensor and the ECM with a DMM. Refer to Circuit Testing
in Wiring Systems. Is the resistance within the specified range? |
0-10 Ω | Go to Step 7 | Go to Step 10 |
| 7 | Measure the resistance of the ECT sensor low reference circuit between the sensor and the ECM with a DMM. Refer to Circuit Testing
in Wiring Systems. Is the resistance within the specified range? |
0-10 Ω | Go to Step 8 | Go to Step 11 |
| 8 |
IMPORTANT:
Do not hold the ECT sensor by the probe.
|
- | Go to Step 9 | Go to Step 12 |
| 9 | Install the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement
. Is the action complete? |
- | Go to Step 13 | - |
| 10 | Repair the high resistance in the ECT sensor signal circuit. Refer to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
- | Go to Step 14 | - |
| 11 | Repair the high resistance in the ECT sensor low reference circuit. Refer to Wiring Repairs
in Wiring Systems. Did you complete the repair? |
- | Go to Step 14 | - |
| 12 | Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement
. Did you complete the replacement? |
- | Go to Step 14 | - |
| 13 | Replace the ECM. Refer to Control Module References
in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? |
- | Go to Step 14 | - |
| 14 |
|
- | Go to Step 2 | Go to Step 15 |
| 15 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? |
- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK |