EGR Cooler Bypass Valve Control Circuit Intermittent (Generic)
The P4055 code means the vehicle's onboard diagnostic system has detected: EGR Cooler Bypass Valve Control Circuit Intermittent (Generic). This is a low severity code.
- Keep driving?
- Yes, but fix soon
- DIY difficulty
- moderate
- Estimated cost
- $100 - $450 (parts and labor)
Best-selling code reader on Amazon. Reads and clears check engine codes on any 1996+ vehicle. Under $30.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Essential for diagnosing sensor codes, checking voltage, and testing circuits. Under $15 and pays for itself on the first job.
Check Price on AmazonAffiliate link -- we earn a commission at no extra cost to you.
Common Symptoms
- Check Engine Light intermittent
- Sporadic EGR cooler operation
- Occasional rough idle
- Intermittent cold start issues
Probable Causes (Ranked by Likelihood)
- Loose bypass valve connector Very High
- Wiring vibration fatigue High
- Solenoid sticking intermittently Moderate
- PCM driver intermittent Low
Step-by-Step Diagnostic Procedure
-
Wiggle test connector while commanding valve on/off
-
Inspect wiring for damage
-
Test valve operation with applied voltage
-
Monitor valve status across drive cycles
Frequently Asked Questions
Is P4055 serious?
No, P4055 is low severity. The system works most of the time.
Can I ignore P4055?
You should not ignore it permanently, but it is safe to drive normally while scheduling a convenient repair.
How do I test the solenoid valve?
Apply 12V directly to the valve and listen for a click.
Explore More
Was this helpful?
Share carcodefinder.com with a friend who needs to decode their check engine light.