Diagnostic Aids

Perform this test only when directed by TEST AA. This test is intended to diagnose:

IAC system.
EGR system.

1) IAC Check Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to TEST KE, step 4). If engine does not run smoothly at part throttle, go to next step.

2) Check For RPM Drop Turn ignition off. Connect a tachometer to engine. Start engine. Disconnect IAC valve. If RPM drops or engine stalls, reconnect IAC valve and go to step 8). If RPM does not drop, go to TEST KE, step 4).

NOTE: A break in step numbering sequence occurs at this point. Procedure skips from step 2) to step 8). No test procedures have been omitted.

8) Check EGR Vacuum Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle could not start previously and still does not start, or if vehicle driveability fault is still present, go to next step. If vehicle did not start previously but starts now, or if driveability symptoms are eliminated, go to TEST DD, step 31).

9) Check EGR Valve Inspect EGR valve for leaks. If valve is fully closed, go to TEST H. If EGR valve is leaking or is not fully seated, repair or replace valve as necessary.