EGR valve jammed open by carbon or soot build-up; Faulty EGR valve motor, solenoid or internal position sensor; Wiring or connector fault (short, chafing, corrosion or poor contact) in the EGR control or feedback circuit; Blocked or restricted EGR passages, or heavy carbon in the intake preventing the valve seating; Vacuum supply or vacuum actuator fault on vacuum-operated EGR systems; Faulty related sensor giving misleading data, such as a manifold pressure or mass airflow sensor; Control unit fault or outdated software, where a manufacturer notice confirms it as a cause.

P042E

EGR A Control Stuck Open.

Generic
Powertrain
Generic code
Medium severity

How this code is built

P: SystemPowertrain
0: Defined bySAE, the same on every car
4: AreaAuxiliary emission controls
2E: FaultThe specific fault in that area

What it means

P042E is the generic code for the exhaust gas recirculation (EGR) valve 'A' being stuck open. The engine control unit commands the valve to a position, compares it with the position feedback or with the effect on intake pressure, airflow or combustion, and sees the valve is open when it should be closed or less open. The valve may be mechanically jammed, or the feedback or control circuit may be faulty.

Symptoms

Engine management light on
Rough or unstable idle, possibly stalling at idle
Hesitation or poor response when pulling away
Reduced power or the car going into limp mode
Hard starting or stalling when coming to a stop
Possible increase in fuel consumption

Possible causes

EGR valve jammed open by carbon or soot build-uplikely
Faulty EGR valve motor, solenoid or internal position sensorlikely
Wiring or connector fault (short, chafing, corrosion or poor contact) in the EGR control or feedback circuitpossible
Blocked or restricted EGR passages, or heavy carbon in the intake preventing the valve seatingpossible
Vacuum supply or vacuum actuator fault on vacuum-operated EGR systemspossible
Faulty related sensor giving misleading data, such as a manifold pressure or mass airflow sensorrare
Control unit fault or outdated software, where a manufacturer notice confirms it as a causerare

How to diagnose

Read all stored and pending codes and note the freeze frame data (engine load, speed, temperature) to see when the fault set, and check for related codes such as other EGR, airflow or boost faults.
Check for manufacturer technical bulletins or known issues for the specific model and engine.
Inspect the EGR valve connector and wiring for damage, heat damage, corrosion, loose pins and chafing, and check any vacuum hoses for splits or disconnection.
With a scan tool, compare commanded and actual EGR position, and use the actuator test to see whether the valve moves and fully closes.
Watch live data for manifold pressure and airflow with the valve commanded closed; an unexpected change suggests it is leaking or stuck open.
Check the EGR valve for free movement and a proper seal, and look for carbon on the valve and in the passages. Follow the procedure for your engine, as access and valve type vary.
Test the power, earth and signal circuits of the valve against the manufacturer's data, and check vacuum supply and actuator operation if the system is vacuum-operated.
After repair, clear the code and road test, confirming the valve position follows the command and the code does not return.

How to fix

Clean the EGR valve and passages if the manufacturer permits it, making sure the valve closes and seals fully; replace the valve if it will not move freely.
Replace the EGR valve or actuator if the motor, solenoid or position sensor is faulty.
Repair or replace damaged wiring, terminals or connectors in the EGR circuit.
Clear carbon from the EGR passages and intake as per the manufacturer's procedure.
Repair vacuum hoses, or replace the vacuum solenoid or actuator, on vacuum-operated systems.
Replace any faulty related sensor, or apply a manufacturer software update only if it is a documented fix for this fault.

Can I keep driving?

Medium severity

The car can usually be driven short distances, but a stuck-open EGR valve can cause stalling, poor running and increased emissions, so get it fixed soon. If it stalls, runs very roughly or goes into limp mode, limit driving as it could become unsafe in traffic.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.