Powertrain, generic · Auxiliary emission controls

P0404 EGR A Control Circuit Range/Performance

Check engine lightOn
EmissionsRelevant
Drive cycleRequired
Limp modePossible

Exhaust gas recirculation (EGR) routes part of the exhaust back into the intake to lower combustion temperature and NOx. P0404 is the function check of the valve drive: on valves with a position sensor the module compares commanded and actual position, and a persistent deviation means the valve sticks, is coked or its drive is too weak (GM diesel 2018 above 10 %, GM petrol 2004 above 15 %, both MIL after two trips). Ford calls it control stuck. Saab's V6 diesel deviates and uses P0404 for a short to positive. EGR control is then switched off and the valve de-energised.

Likely causes

Valve coked or stiff
Valve drive (motor, gear) worn
Position sensor in the valve inaccurate
Supply voltage too low or ground fault

Symptoms

  • Check engine light on
  • EGR deactivated
  • Rough idle or jerking if the valve hangs open
  • Diesel: possibly reduced power

Repair estimate

DifficultyMediumDIY possible
Parts and labour€100–700
Time1–3 h

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

What to check first

  1. Clean or replace the EGR valve
  2. Check position sensor signal

Parts involved

egr valveegr valve actuatoregr wiringengine control module

Related codes

P0403P042EP0401P0405

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