P042E code meaning
EGR A Control Stuck Open
Powertrain system Generic code P04xx codes Check engine light
What P042E means
Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P042E means the position-controlled EGR valve A is more open than commanded and cannot be closed. GM's diesels of 2016/17 set it when the valve stays too far open despite maximum closing duty (about 1–8 s); the 2018 tables check after switch-off whether it is below 5 % within 2 s – both with MIL on the first trip. Ford gasoline engines compare the position with limits for 4 s, Ford diesels a deviation above 15 % for 25 s. Too much EGR causes rough idle, stalling and smoke; EGR control is switched off.
P042E at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor1 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P042E
- Check engine light on (GM after one trip)
- Rough idle, stalling, starting problems
- Loss of power, possibly limp mode
- Diesel: smoke, higher soot load
Common causes of P042E
- Most likelyValve or disc coked, does not close
- PossibleActuator motor, gear or return spring faulty
- PossiblePosition sensor in the valve reads wrong
- Less likelyWeak supply to the drive or connector fault
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 valve position sensorEngine control module
What each part of P042E 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). |
| 2E | The exact fault in that area. |
What to do next
- Note P042E 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 P042E
What does P042E mean?
P042E means "EGR A Control Stuck Open". 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 P042E?
Drive gently and only to a workshop. With P042E the car can go into limp mode (reduced power) to protect itself.
Will P042E fail an emissions test?
Yes, it can. P042E 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 P042E to fix?
Difficulty: medium. A typical repair takes 1 to 4 hours of work. This is a job for a workshop.
Will P042E clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.