P042F: EGR A Control Stuck Closed

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P042F means EGR valve A does not follow the opening command: its actual position stays more closed than commanded although the actuator works with high opening duty. GM's diesels of 2016/17 set it after about 1–8 s with MIL on the first trip; a GM bulletin covers it on the 2017 Cruze diesel. Ford petrol engines use position limits for 4 s; Ford diesels report both directions under P042E. With too little EGR, NOx rises, petrol engines may knock and P0401 can follow.

Symptoms

• Check engine light on (GM after one trip)
• Usually no driveability problems
• Possibly pinging (petrol) or higher NOx

Most likely causes

• Valve coked or seized in the closed position
• Actuator motor or gear weak or faulty
• Position sensor or connector gives a wrong value
• Icing in winter (temporary)

What to check, in order

Start with the simplest. You can tick off each step.

1. Check the connector and any vacuum hoses
2. Use the scanner to command the movement and compare the actual position with the requested one.
3. Use live data to compare the commanded opening with the actual opening
4. Clean the valve and passages if they are clogged with carbon
5. Test the actuator with the scanner
6. Replace the valve if it still does not follow the command after cleaning

Good to know

• Repair difficulty: medium
• It affects emissions.

What each character of P042F means

• P: Powertrain: engine and transmission
• 0: Generic code: same on every make
• 4: Emissions
• 2F: Specific fault in that system

Frequently asked questions

Can I keep driving with code P042F?

You can normally drive in moderation, but get it repaired soon: if the valve is stuck open, the engine may idle very poorly.

What causes code P042F?

The most common causes are: valve coked or seized in the closed position; actuator motor or gear weak or faulty; position sensor or connector gives a wrong value.

Related codes

• P042EEGR A Control Stuck Open
• P0401EGR A Flow Insufficient Detected
• P0404EGR A Control Circuit Range/Performance
• P0405EGR Sensor A Circuit Low
• P045FEGR B Control Stuck Closed

Sources

• gsi.ext.gm.com: 16OBDG04 Engine Diagnostics
• gsi.ext.gm.com: 17OBDG04 Engine Diagnostics
• fordservicecontent.com: OBD Operations Summary Gasoline 2020 2023
• static.nhtsa.gov: MC 10140411 9999

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.