Reductant Heater "A" Control Circuit High
This code means the PCM/ECM has detected a high-voltage control circuit condition affecting reductant heater "a. This can keep the emissions system from working correctly, which may raise tailpipe emissions, reduce fuel economy, and prevent readiness monitors from completing.
What You Might Notice
- Check Engine Light illuminated
- Failed emissions or readiness monitor
- Reduced fuel economy
- Cold-start drivability issue
- No obvious symptom besides the warning light
Most Common Causes
- 1
Short to voltage or an internally failed component
- 2
Wiring damage or poor electrical connection
- 3
Carbon buildup, restriction, or exhaust leak
- 4
Vacuum leak or pressure hose issue
- 5
PCM/ECM fault or outdated calibration
How to Diagnose It
- 1
Check Short to voltage or an internally failed component — Inspect for signs of failure and test before replacing.
- 2
Check Wiring damage or poor electrical connection — Inspect for signs of failure and test before replacing.
- 3
Check Carbon buildup, restriction, or exhaust leak — Inspect for signs of failure and test before replacing.
- 4
Check Vacuum leak or pressure hose issue — Inspect for signs of failure and test before replacing.
- 5
Check PCM/ECM fault or outdated calibration — Inspect for signs of failure and test before replacing.
How to Fix It
- 1
Inspect the sensor, valve, heater, and related hoses or pipes
- 2
Repair wiring or connector damage
- 3
Clean carbon buildup or repair leaks/restrictions
- 4
Replace the failed emissions component if testing confirms it
- 5
Clear the code and run the monitor to verify the fix
Need a deeper diagnosis?
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