Test Description
The numbers below refer to the step numbers in the diagnostic table.
- 5: This step tests for excessive resistance in the ECT circuit.
- 6: This step isolates the condition. If the temperature changes, test for a condition in the low reference circuit. If the temperature remains the same test the signal circuit for a condition.
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connect End View Reference: Engine Control Module (ECM) Connector End Views or Engine Controls Connector End Views |
||||
| 1 | Did you perform the Diagnostic System Check - Engine Controls? | - | Go to Step 2 | Go to Diagnostic System Check - Engine Controls |
| 2 | Is the engine cooling system low on coolant? | - | Go to Loss of Coolant in Engine Cooling | Go to Step 3 |
| 3 | Is the customer's concern that the engine does not reach operating temperature or that the heater output is low? | - | Go to Thermostat Diagnosis in Engine Cooling | Go to Step 4 |
| 4 |
IMPORTANT:
Return to this diagnostic procedure after you complete the thermostat diagnosis. Test for the correct operation of the thermostat. Refer to Thermostat Diagnosis
in Engine Cooling.Did you find and correct the condition? |
- | Go to Step 13 | Go to Step 5 |
| 5 |
|
129°C (264°F) | Go to Step 9 | Go to Step 6 |
| 6 |
|
129°C (264°F) | Go to Step 7 | Go to Step 8 |
| 7 | Test the low reference circuit of the ECT sensor for high resistance. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 13 | Go to Step 10 |
| 8 | Test the signal circuit of the ECT sensor for high resistance. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 13 | Go to Step 10 |
| 9 | Test for shorted terminals and poor connections at the ECT sensor. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 13 | Go to Step 11 |
| 10 | Test for shorted terminals and poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections
and Connector Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 13 | Go to Step 12 |
| 11 | Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement
. Did you complete the replacement? |
- | Go to Step 13 | - |
| 12 | Replace the ECM. Refer to Engine Control Module (ECM) Replacement
. Did you complete the replacement? |
- | Go to Step 13 | - |
| 13 |
|
- | Go to Step 2 | Go to Step 14 |
| 14 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? |
- | Go to Diagnostic Trouble Code (DTC) List | System OK |