Diagnostic Aids

Perform this test only when directed by CIRCUIT TEST AA, CIRCUIT TEST AB or CIRCUIT TEST AC. This test is intended to diagnose following.

• IAC system
• EGR system
• MAF system

To prevent replacing good components, be aware following non-EEC-IV areas may be at fault.

• Faulty power or ground connections
• Secondary ignition (distributor cap, rotor, wires, coil and plugs)
• Engine mechanical components (compression, timing, valves, etc.)

1) IAC Check  Try to start engine at part throttle. If engine starts and runs smoothly at part throttle, go to CIRCUIT TEST KE, step 4). If engine does not run as described, go to step 3). If engine starts and idles smoothly, go to next step.

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

3) Check EGR Vacuum  If vehicle is not equipped with EGR system, go to CIRCUIT TEST H, step 2). Disconnect and plug vacuum line at EGR valve. Attempt to start engine. If vehicle did not start previously but starts now or if driveability symptoms are eliminated, go to CIRCUIT TEST DN, step 42) (vehicles with EVP) or CIRCUIT TEST DL, step 50) (except vehicles with EVP). If vehicle could not start previously and still does not start, or if vehicle driveability fault is still present, go to next step.

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