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Home >> Buick >> 1995 >> Park Avenue Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes >> ECM/Pcm Code Charts >> Code P0401, (EGR) Flow Test Failure >> Diagnostic Aids

Diagnostic Aids

An intermittent may be caused by a broken wire inside insulation. Check for:

Inspect PCM harness connectors for backed out EGR control circuit terminal, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

If connections and harness are okay, monitor a DVOM connected between PCM EGR control circuit terminal and ground while moving related connectors and wiring harness. If failure is induced, voltage reading will change.

NOTE: Check exhaust system for blockage (possibly a plugged converter) if EGR valve shows signs of excessive heat. Repair cause of restricted exhaust system as necessary. Injector stuck open may be due to stuck injector pintle, grounded driver circuit or possible faulty PCM. If conditions are not present, oil should be checked for possible fuel contamination.
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