Code 63, 64 Or 65, EGR Flow Check Error

On a closed throttle coastdown, ECM energizes solenoids inside of EGR valve and monitor changes in RPM and O2 sensor activity. If expected changes do not occur, appropriate code will be set. Code 26 in conjunction with Code 63, 64 or 65 indicates a possible quad-driver problem. Before using this chart, use Code 26 chart, clear codes and test drive to see if EGR codes reset.

NOTE: Test numbers refer to test numbers on diagnostic chart.

With ALDL not grounded and engine not running, test light should not illuminate.
With ALDL test terminal B grounded, ECM should energize the EGR solenoids by providing a ground at the ECM/ This will cause the test light to illuminate when touched to EGR harness terminals A, B and C. If test light does not illuminate, check for open circuit or faulty ECM.

NOTE: If digital EGR valve shows signs of excessive heat (i.e. a melted condition), check exhaust system for blockage (possible plugged converter).

Fig 1: Code 63, 64 or 65 Schematic, EGR Flow Check Error

NOTE: Use schematic to identify terminal referenced in the following flow chart.

Fig 2: Code 63, 64 Or 65, EGR Flow Check Error Flow Chart (Without Tech 1)