P1001
PowertrainObd Systemlow severityManufacturer-specificKOER Self-Test Not Able to Complete
What P1001 Means
The Key On Engine Running (KOER) self-test was unable to complete. This indicates the PCM could not finish its powered-on engine running diagnostic routine, possibly due to another existing fault or test conditions not being met.
Symptoms
- Check Engine Light
- Self-test cannot complete
- Other DTCs may be stored
Common Causes
- Existing DTCs preventing test completion
- Engine not at operating temperature
- Accessories not turned off during test
- PCM malfunction
Diagnostic Steps
- Ensure engine is fully warmed up before running KOER test
- Turn off all accessories (A/C, lights, radio)
- Check for and resolve any other stored DTCs first
- Retry KOER self-test
Where to start: Resolve other DTCs first, then re-run KOER self-test with engine at operating temperature.
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