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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What Are the Symptoms of P0477?
- Check Engine Light on
- Exhaust pressure too high or uncontrolled
- DPF issues
- Reduced engine performance
What Causes P0477? (Most Likely First)
- Short to ground in control valve wiring Very High
- Internally shorted valve solenoid High
- Corroded connector Moderate
- PCM driver fault Low
Can I Still Drive with P0477?
Short distances only. P0477 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
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
How Do You Diagnose P0477?
-
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
Which Vehicles Commonly Get P0477?
- 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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