Exhaust Gas Recirculation Control Circuit High
The P0490 code means the vehicle's onboard diagnostic system has detected: Exhaust Gas Recirculation Control Circuit High. This is a moderate severity code.
- Keep driving?
- Short distances only
- DIY difficulty
- moderate
- Estimated cost
- $100 - $450 (parts and labor)
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Common Symptoms
- Check Engine Light on
- EGR valve stuck open
- Rough or unstable idle
- Engine stalling at idle
Probable Causes (Ranked by Likelihood)
- Short to power in EGR control circuit wiring Very High
- Failed EGR solenoid stuck energized High
- ECM EGR driver circuit stuck high Moderate
- Aftermarket wiring modification in EGR circuit Low
Step-by-Step Diagnostic Procedure
-
Disconnect the EGR valve connector and check for voltage on the control wire with key on; voltage present indicates a short to power
-
Measure EGR solenoid resistance; compare to specification
-
Inspect the wiring harness for the EGR circuit for chafing against other wires that could cause a short to power
-
Use a scan tool to command the EGR off and verify the circuit responds correctly
Frequently Asked Questions
Can P0490 cause stalling?
Yes. If the EGR valve is stuck open due to a circuit high condition, it allows too much exhaust gas into the intake at idle. This displaces fresh air and fuel, causing rough idle or stalling.
What does circuit high mean for the EGR?
Circuit high means the ECM detects voltage on the EGR control circuit above the maximum threshold. This typically indicates a short to battery voltage in the wiring keeping the EGR solenoid energized.
How do I test the EGR solenoid?
Disconnect the EGR valve connector and measure resistance across the solenoid terminals with an ohmmeter. Compare the reading to the manufacturer specification, typically 20-40 ohms. Also check for shorts to the housing.
Sources
This page is built from documented references. Verify against your own service info before repair work.
P0490 on Diesel, EV & Equipment
The same code ID appears across other engines and platforms. The diagnostic flow varies by manufacturer — these are the platform-specific breakdowns:
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