Diagnosis By Symptom Test

The DIAGNOSIS BY SYMPTOM TEST is divided into specific engine sections. Each section will describe testing procedures and codes for that engine. Use appropriate DIAGNOSIS BY SYMPTOM TEST. The CIRCUIT TESTS  are common to all engines, unless noted in test procedures.

Use this test procedure ONLY when directed to do so by results of QUICK TEST  or steps in CIRCUIT TESTS  . Follow test procedure carefully.

1. When engine stalls in operation, misfires, lacks power, idles roughly, or has erratic RPM, perform the following checks:
   • Check for, and repair, any bad ground or power connections.
   • Check ignition components (cap, rotor, wires, coil and plugs).
   • Check basic engine components (valves, cam timing, compression, etc.).
   • Perform SYSTEM CHECK, ISC Check, MAP Check, and EGR Check. Use TEST QQ - SYSTEM CHECK  , steps 1), 2), and 3).
   • Perform CYLINDER BALANCE TEST  . See QUICK TEST  DIAGNOSTIC AIDS in this article.
2. If fuel pump is always on (noise coming from rear of vehicle with key off), go to TEST Y - INERTIA SWITCH  , step 12).
3. If shift indicator light is always on or off, go to TEST FF - SHIFT INDICATOR LIGHT  , step 1).
4. If engine idle speed is low with A/C on, go to TEST O - NEUTRAL A/C SWITCH  , step 9).
5. If A/C does not cut-off during wide open throttle (WOT), go to TEST GG - A/C CUT-OUT  , step 1).
6. If detonation (engine knock) occurs due to improper EGR valve function, check EGR and/or exhaust gas recirculation system.
7. If engine stalls during QUICK TEST  due to faulty Idle Speed Control (ISC) operation, go to TEST DD - IDLE SPEED CONTROL  , step 4).
8. If gasoline fumes accumulate in engine compartment, go to TEST CC - CANP CHECK  , step 1).