Exhaust Pressure Control Valve Circuit Intermittent
The P0479 code means the vehicle's onboard diagnostic system has detected: Exhaust Pressure Control Valve Circuit Intermittent. 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 P0479?
- Intermittent Check Engine Light
- Exhaust brake works sometimes
- DPF regeneration inconsistent
- Occasional performance changes
What Causes P0479? (Most Likely First)
- Loose exhaust pressure control valve connector Very High
- Intermittent wire break from exhaust heat High
- Valve sticking intermittently Moderate
- Vibration-induced connection fault Low
Can I Still Drive with P0479?
Short distances only. P0479 is rated moderate severity. Keep trips short and get it diagnosed soon rather than waiting for symptoms to worsen.
Frequently Asked Questions
Why does the exhaust brake work sometimes?
An intermittent connection to the exhaust pressure control valve means it sometimes receives the command signal and sometimes does not.
Can exhaust heat cause intermittent faults?
Yes, thermal cycling (heating and cooling) causes wiring insulation to crack and connectors to expand and contract, creating intermittent connections.
Should I replace the valve or fix wiring?
Diagnose with the wiggle test first. If the connector is the problem, repair it. If the valve sticks mechanically, replace it.
Mechanics Guide Step-by-step diagnosis
How Do You Diagnose P0479?
-
Monitor valve command vs. response during driving.
-
Wiggle test on connector and wiring.
-
Inspect for heat-damaged wiring.
-
Check valve for intermittent mechanical sticking.
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 P0479?
- 2010-2020 Ford F-250 (6.7L Diesel)
- 2012-2019 Chevrolet Silverado 2500 (6.6L Duramax)
- 2008-2018 Ram 2500 (6.7L Cummins)
- 2011-2020 GMC Sierra 2500 (6.6L Duramax)
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