Diagnostic Procedures
- Perform On-Board Diagnostic (OBD) System Check. See BASIC TESTING article. Go to next step.
- If any ECT DTCs are set, diagnose affected DTC before proceeding. If no ECT DTCs are set, go to next step.
- Check coolant level. If coolant level is low, go to step 9) If coolant level is okay, go to next step.
- Allow engine to cool completely. Turn engine on and allow it to idle. Using scan tool, monitor ENG COOL TEMP. If temperature increases to 70°F (21°C) within 2 minutes, see DIAGNOSTIC AIDS . If specified temperature is not reached within 2 minutes, go to next step.
- Check thermostat operation. If thermostat is operating correctly, go to next step. If thermostat is not operating correctly, go to step 9).
- Compare actual coolant temperature with scan tool ECT value. If temperatures are close in value, go to step 9). If temperatures are not close in value, go to next step.
- Turn ignition off. Disconnect PCM. Using a DVOM, measure ECT resistance at PCM connector and compare DVOM readings with ECT SENSOR TEMPERATURE VS. RESISTANCE VALUES . If chart values equal readings, go to step 12). If chart values do not equal readings, go to next step.
- Check for high resistance in wiring related to ECT sensor and for poor connections at ECT sensor and PCM. If a problem is found, go to step 10). If no problem is found, go to step 11).
- Repair cooling system as necessary. Retest system.
- Repair terminal as necessary. Retest system.
- Replace ECT sensor. Retest system.
- Replace PCM. Program replacement PCM using required equipment. Retest system.
ECT SENSOR TEMPERATURE VS. RESISTANCE VALUES
| Temperature °F (°C) | Ohms |
|---|---|
| 212 (100) | 177 |
| 176 (80) | 332 |
| 140 (60) | 667 |
| 113 (45) | 1188 |
| 95 (35) | 1802 |
| 77 (25) | 2796 |
| 59 (15) | 4450 |
| 41 (5) | 7280 |
| 23 (-5) | 12300 |
| 5 (-15) | 21450 |
| -22 (-30) | 52700 |
| -40 (-40) | 100700 |