ECM cannot control the check engine light circuit properly.
Common symptoms
- No check engine light at key-on
- Stored P0650
Typical causes
- Burned out MIL bulb in cluster
- Cluster fault
- Wiring to MIL
What scanner do you need?
Enhanced OBD2 scanner (live data graphs, freeze frame, battery voltage test)
Use live data and freeze frame to confirm the fault before replacing parts. ABS, SRS, and network U-codes usually require a full-system scanner.
Diagnostic tips
- Record freeze frame data when the code first sets
- Clear the code only after fixing the root cause
- Check for related pending codes that point to a common issue
- Verify battery voltage is above 12.4V before chasing sensor codes