GM Grand Am/Achieva/Calais/Skylark/Somerset 1985-98

Diagnosis and Testing


Service Precautions

The HEI coil secondary voltage output capabilities can exceed 40,000 volts. Avoid body contact with the HEI high voltage secondary components when the engine is running, or personal injury may result.

To avoid damage to the ECM or other ignition system components, do not use electrical test equipment such as battery or AC powered voltmeter, ohmmeter, etc. or any type of tester other than specified.

When making compression checks, disconnect the ignition switch feed wire at the distributor.
Never allow the tachometer terminal to touch ground, as damage to the module and/or ignition coil can result.
To prevent Electrostatic Discharge damage, when working with the ECM, do not touch the connector pins or soldered components on the circuit board.
When handling a PROM, CAL-PAK or MEM-CAL, do not touch the component leads. Also, do not remove the integrated circuit from the carrier.
Never allow welding cables to lie on, near or across any vehicle electrical wiring.
Leave new components and modules in the shipping package until ready to install them.
When performing electrical tests on the system, use a high impedance multimeter, digital voltmeter (DVM) J-34029-A or equivalent.
Never pierce a high tension lead or boot for any testing purpose; otherwise, future problems are guaranteed.

Ignition System CheckSee Figures 1, 2, 3 and 4

The accompanying wire schematics and charts can be used to diagnose and troubleshoot some HEI system component problems.

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Fig. Fig. 1: Ignition system diagnostic check-1985-86 2.5L engine

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Fig. Fig. 2: Schematic of ignition system wiring-1985-86 2.5L engine

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