P0490EGR A Control Circuit High
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0490 means the drive circuit of EGR valve A is shorted to battery voltage, or its output stage sees overcurrent. GM's Duramax LML sets it at 0.5 Ω or less to the supply for 3 s, GM's 2017 diesels at an H-bridge current above 8 A (160 of 200 samples), Ford diesels after 0.35 s – MIL after two trips. The output stage switches off for protection and the valve falls into its spring position, closed; EGR is off.
- What you may notice
- Check engine light on
- EGR switched off, usually no noticeable change
- Higher NOx
- Likely causes
- LikelyHarness shorted to a supply wire (chafing)
- PossibleEGR valve with shorted turns (low resistance, overcurrent)
- PossibleMoisture in the connector
- RareDriver in the engine module
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Often possible to do yourself.Typical cost: €50 – €700
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.