Exhaust Pressure Control Valve Circuit Low
The P0477 code means the vehicle's onboard diagnostic system has detected: Exhaust Pressure Control Valve Circuit Low. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- hard
- Estimated cost
- $150 - $600 (parts and labor)
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Common Symptoms
- Check Engine Light on
- Exhaust pressure too high or uncontrolled
- DPF issues
- Reduced engine performance
Probable Causes (Ranked by Likelihood)
- Short to ground in control valve wiring Very High
- Internally shorted valve solenoid High
- Corroded connector Moderate
- PCM driver fault Low
Frequently Asked Questions
What does circuit low mean for the exhaust pressure valve?
The PCM detects lower resistance or voltage than expected, usually from a short to ground in the solenoid wiring.
Can excessive soot damage the valve electrically?
Conductive soot buildup between terminals can create a partial short, leading to circuit low conditions.
Is P0477 a fire hazard?
No, but uncontrolled exhaust pressure can cause excessive back pressure that reduces engine performance and increases exhaust temperatures.
Mechanics Guide Step-by-step diagnosis
Step-by-Step Diagnostic Procedure
-
Measure valve solenoid resistance. Below spec indicates short.
-
Check wiring for short to ground.
-
Inspect connector for corrosion.
-
Disconnect valve and verify code changes.
Sources 2
This page is built from documented references. Verify against your own service info before repair work.
- SAE J2012Diagnostic Trouble Code Definitions (defines the generic OBD-II code ranges)
- Cross-checked against the SAE J2012:2002 DTC table (2026-08-27)archived scan of the SAE standard — readable copy, not SAE’s current edition
Commonly Affected Vehicles
- 2010-2020 Ford F-250 (6.7L Diesel)
- 2012-2019 Ram 2500 (6.7L Cummins)
- 2008-2018 Chevrolet Silverado 2500 (6.6L Duramax)
- 2011-2020 GMC Sierra 2500 (6.6L Duramax)
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