What P0403 means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx.
How the engine computer detects it
P0403 concerns the electrical drive of the EGR valve – solenoid, stepper motor, DC motor or vacuum regulator. The module checks the output and sets the code for an open circuit (GM: above 200 kΩ, MIL after two trips; Ford after 4 s, MIL after two trips). Newer systems report shorts separately as P0489 (low) and P0490 (high); Ford and older GM systems include them in P0403. EGR is then switched off for the rest of the trip.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Check engine light on
- EGR switched off: pinging (gasoline) or higher NOx
- Usually no loss of power
Common causes
- Connector at the EGR valve corroded or loose Most likely
- Broken control or supply wire Possible
- Coil or motor in the EGR valve burnt out Possible
- Driver in the engine module Less likely
How to diagnose P0403
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: egr valve, egr valve actuator, egr wiring, engine control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0403 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Chevrolet Volt | 2016–2017 | 4 | — |
Counts of owner complaints to the NHTSA that mention P0403 (8 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 4
- Auxiliary emission controls
- 03
- Specific fault
Questions drivers ask
Can I drive with code P0403?
Usually yes for a short time, if the car drives normally, the temperature gauge reads normal and the check engine light is steady. If the light flashes, the engine loses power or overheats, or other warning lights come on, pull over and have it checked.
Will my car pass an emissions inspection with P0403?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Will P0403 clear by itself?
The light can go off after several drive cycles without the fault, but the code returns if the cause is still there. After a repair, the readiness monitors need a full drive cycle before an inspection.
Can I fix P0403 myself?
Often yes, with an OBD-II scanner and basic tools. Difficulty: easy. Start with the cheapest checks before replacing expensive parts.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0403. They can point to a shared cause, so it's worth checking them together.
- P0135O2 Sensor Heater Circuit Bank 1 Sensor 14 complaints
- P0405EGR Sensor A Circuit Low4 complaints
- P0443EVAP System Purge Control Valve A Circuit4 complaints
- P0030HO2S Heater Control Circuit (Bank 1 Sensor 1)3 complaints
- P0031HO2S Heater Control Circuit Low (Bank 1 Sensor 1)3 complaints
- P0458EVAP System Purge Control Valve A Circuit Low3 complaints
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.