Diagnostic Aids
WARNING: This page is about a different car, the 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 Chevrolet TrailBlazer, and 2004 Buick Rainier. However, it is still accessible from the selected car via links, so may be relevant.
- If a short to a separate 5-volt source occurs, this DTC may set.
- After starting the engine, the ECT should rise steadily, then stabilize when the thermostat opens.
- Use the Temperature vs. Resistance table in order to test the ECT sensor. A skewed sensor could result in poor driveability conditions. Refer to Temperature vs Resistance .
- If the condition is suspected of being intermittent, refer to Intermittent Conditions .
DTC P0118
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module (PCM) 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 | Observe the ECT sensor parameter with a scan tool. Is the ECT sensor parameter less than the specified value? |
-38°C (-36°F) | Go to Step 4 | Go to Step 3 |
| 3 |
|
- | Go to Step 4 | Go to Diagnostic Aids |
| 4 |
|
5.2 V | Go to Step 5 | Go to Step 6 |
| 5 |
IMPORTANT:
If a short to voltage occurs, the ECT sensor may be damaged. Test the ECT signal circuit for a short to voltage. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems.Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 12 |
| 6 |
|
138°C (280°F) | Go to Step 10 | Go to Step 7 |
| 7 |
|
138°C (280°F) | Go to Step 9 | Go to Step 8 |
| 8 | Test the signal circuit of the ECT sensor for a high resistance or an open. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 12 |
| 9 | Test the low reference circuit of the ECT sensor for a high resistance or an open. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 12 |
| 10 | Test the ECT signal circuit for a short to any 5-volt reference circuit. Refer to Circuit Testing
and Wiring Repairs
in Wiring Systems. Did you find and correct the condition? |
- | Go to Step 15 | Go to Step 11 |
| 11 | Test for an intermittent and for a poor connection 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 15 | Go to Step 13 |
| 12 | Test for an intermittent and for a poor connection at the PCM. 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 15 | Go to Step 14 |
| 13 | Replace the ECT sensor. Refer to Engine Coolant Temperature (ECT) Sensor Replacement
. Did you complete the replacement? |
- | Go to Step 15 | - |
| 14 | Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement
. Did you complete the replacement? |
- | Go to Step 15 | - |
| 15 |
|
- | Go to Step 2 | Go to Step 16 |
| 16 | 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 |