P0490 code meaning
EGR A Control Circuit High
Powertrain system Generic code P04xx codes Check engine light
What P0490 means
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.
P0490 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 3 hours
- Clears after repairAfter a drive cycle
Symptoms of P0490
- Check engine light on
- EGR switched off, usually no noticeable change
- Higher NOx
Common causes of P0490
- Most likelyHarness shorted to a supply wire (chafing)
- PossibleEGR valve with shorted turns (low resistance, overcurrent)
- PossibleMoisture in the connector
- Less likelyDriver in the engine module
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
EGR valveEGR valve actuatorEGR wiringEngine control module
What each part of P0490 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 4 | Area: auxiliary emission controls (catalytic converter, EGR, EVAP). |
| 90 | The exact fault in that area. |
What to do next
- Note P0490 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0490
What does P0490 mean?
P0490 means "EGR A Control Circuit High". Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. It is a generic code, so it means the same on every make.
Is it safe to drive with P0490?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will P0490 fail an emissions test?
Yes, it can. P0490 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0490 to fix?
Difficulty: medium. A typical repair takes 0.5 to 3 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will P0490 clear itself after the repair?
After the repair the car has to complete a drive cycle (a mix of city and highway driving) before the test runs again. Until then the readiness monitor shows "not ready", which can fail an inspection.