GM Lumina/Grand Prix/Cutlass Supreme/Regal 1988-1996

Diagnosis and Testing



The ignition coil's secondary voltage output capabilities can exceed 40,000 volts. Avoid body contact with the IDI 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 performing electrical tests on the system, use a high impedance multimeter, digital voltmeter (DVM) J-34029-A or equivalent. Use of a 12 volt test light is not recommended.
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 pierce a high tension lead or boot for any testing purpose; otherwise, future problems are guaranteed.
Leave new components and modules in the shipping package until ready to install them.
Never detach any electrical connection with the ignition switch ON unless instructed to do so in a test.


See Figure 1 and 2

Click image to see an enlarged view

Fig. Fig. 1: IDI ignition system circuits-2.3L engine

Click image to see an enlarged view

Fig. Fig. 2: IDI ignition system diagnosis-2.3L engine

The ECM uses information from the MAP and coolant sensors, in addition to rpm to calculate spark advance as follows:

  1. Low MAP output voltage - more spark advance
  3. Cold engine - more spark advance
  5. High MAP output voltage - less spark advance
  7. Hot engine - less spark advance

Therefore, detonation could be caused by low MAP output or high resistance in the coolant sensor circuit. And poor performance could be caused by high MAP output or low resistance in the coolant sensor circuit.

To diagnose what may be an ignition-related problem, first check for codes. If codes, exist, refer to the corresponding diagnostic information in Driveability & Emissions Controls . Otherwise, the accompanying charts may be helpful.