Engine Coolant Temperature (ECT) sensor circuit malfunction code may be set by
- ECT sensor malfunction.
- Open or short circuit between PCM connector C254 terminal No. 4 and ECT sensor terminal No. 1.
- Open or short circuit between PCM connector C254 terminal No. 6 and ECT sensor terminal No. 2.
- Check ECT sensor and PCM connections. Repair as needed. Go to next step.
- Check PCM pin voltage at connector C254 terminal No. 4. See «PIN VOLTAGE CHARTS»(ref-25101) article. If voltage is okay, go to step 6). If voltage is out of specification go to next step.
- Disconnect ECT sensor. Turn ignition on. Check voltage at ECT sensor connector terminal No. 1. If 5 volts exists, go to next step. If 5 volts does not exist, repair short between PCM connector C254 terminal No. 4 and ECT sensor connector terminal No. 1.
- Check continuity between PCM connector C254 terminal No. 8 and ECT sensor connector terminal No. 2. If continuity exists, go to next step. If continuity does not exist, repair or replace wiring.
- Check ECT sensor. See ECT SENSOR in «SYSTEM/COMPONENT TESTS»(ref-25100) article. If sensor is bad, replace sensor. If sensor is okay, go to next step.
- Clear code. Recheck codes. If code returns, replace PCM. If code does not return, problem is intermittent.