COLD STARTABILITY IGNITION DIAGNOSIS

MODELS/YEARS: 1983-84 FIRENZA MODELS EQUIPPED WITH 2.0L ENGINE (VIN CODE P), AUTOMATIC TRANSAXLE & FEDERAL EMISSIONS SYSTEM

On vehicles repaired per the cold startability bulletins (Dealer Technical Bulletins 84-T-20 and 84-T-20A), normal check engine light procedures for trouble code 42 will no longer apply. This trouble code can no longer be set on these vehicles. On vehicles exhibiting the driveability conditions listed below, refer to the following supplemental diagnostic information.

If the supplemental diagnostic procedures do not repair the condition, then the cold start repairs are not the cause and normal diagnostic procedures should be used.

DIAGNOSTIC SUPPLEMENT - 1983-84 vehicles repaired per cold startability bulletins.

CONDITION

Engine Cranks But Will Not Run or Engine Disconnect "Set Timing" connector, Starts But Immediately Stops. See illustration for "Set Timing" connector location. If engine starts see Code Chart 42 for open or short to ground in EST CKT 423.

Hard Start -10 degrees F (-23 degrees C). Check: May Hear Metallic "Knock" during crank. - Open circuit 906 - Open relay ground - Faulty relay (will not close during crank)

Spark Knock Heavy Loads. Loss of Check and note timing. Disconnect Performance and Fuel Economy. "Set Timing" connector and again note timing. See illustration for "Set Timing" connector location. If no change check: - Open or short to grou nd in bypass CKT 424. See Code 42 - Relay contacts stuck closed

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.