Symptom Checks

Check the following items:

• Check the following Parameter Identification (PID) values: DPFEGR, ECT, IAC, LONGFT 1, LONGFT 2, VPWR and VREF. See PIN VOLTAGE CHARTS article. On some vehicles, all PIDs may not be applicable.
• Check fuel delivery system. See CIRCUIT TEST HC in TESTS W/CODES article.
• Check secondary ignition system. See CIRCUIT TEST JB in TESTS W/CODES article.
• Check exhaust system. See CIRCUIT TEST HF in TESTS W/CODES article.
• Check engine compression. Check engine mechanical condition. Check intake manifold gasket, camshaft and valves.
• Ensure transmission is functioning properly. If engine stalls during transmission engagement, check transmission solenoids. See TRANSMISSION SERVICE & REPAIR article.
• Check for binding/dragging brakes.
• Check charging system. Check customer driving habits (i.e., driving with excessive loads). If no problems are indicated, return to SYMPTOM DIAGNOSIS  to identify any additional symptoms or go to CIRCUIT TEST Z in TESTS W/CODES article and check for intermittent faults.