Powertrain, generic · Auxiliary emission controls

P042E EGR A Control Stuck Open

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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 petrol 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.

Likely causes

Valve or disc coked, does not close
Actuator motor, gear or return spring faulty
Position sensor in the valve reads wrong
Weak supply to the drive or connector fault

Symptoms

  • Check engine light on (GM after one trip)
  • Rough idle, stalling, starting problems
  • Loss of power, possibly limp mode
  • Diesel: smoke, higher soot load

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€150–900
Time1–4 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

egr valveegr valve actuatoregr valve position sensorengine control module

Related codes

P042FP0404P0405P0402P0489

References: gsi.ext.gm.com, gsi.ext.gm.com, fordservicecontent.com, fordservicecontent.com.