GM: Electra/Park Avenue/Ninety-Eight 1990-1993

Diagnosis and Testing



The ignition coil's secondary voltage output capabilities can exceed 40,000 volts. Avoid body contact with the C 3 I high voltage secondary components when the engine is running, or personal injury may result.

To avoid damage to the ecm/pcm 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.

To properly diagnosis the ignition systems and their problems, it will be necessary to refer to the diagnostic charts in the fuel injection section. Locate the charts that apply to the vehicle in question and follow them from start to stop.
When performing electrical tests on the system, use a high impedance multimeter or quality digital voltmeter (dvm). 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.
Do not allow extension cords for power tools or droplights to lie on, near or across any vehicle electrical wiring.
Leave new components and modules in the shipping package until ready to install them.


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Fig. Fig. 1 aldl connector terminal identification

The Assembly Line Diagnostic Link (aldl) connector is used for communicating with the ecm. It is usually located under the instrument panel and is sometimes covered by a plastic cover labeled `diagnostic connector.' Codes stored in the ecm's memory can be read through a handheld diagnostic scanner plugged into the aldl connector. If a scanner is not available, the codes can also be read by jumping from terminal A to B of the aldl connector and counting the number of flashes of the Service Engine Soon light, with the ignition switch turned on .

Refer to for a more detailed look diagnostic codes, what they mean and how to diagnose them.


To clear codes from the ecm memory, the ecm power feed must be disconnected for at least 30 seconds. Depending on the vehicle, the ecm power feed can be disconnected at the positive battery terminal pigtail, the inline fuseholder that originates at the positive connection at the battery or the ecm fuse in the fuse block. The negative battery cable may also be disconnected; however, other on-board memory data, such as preset radio tuning, will also be lost.

Also, if battery power is lost, computer relearn time is approximately 5-10 minutes. This means the computer may have to re-calibrate components which set up the idle speed and the idle may fluctuate while this is occurring.


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Fig. Fig. 2 Ignition system wiring schematic-Vin C engine

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Fig. Fig. 3 Ignition system wiring schematic-Vin C and 1 engines

  1. Check for codes. If any are found, refer to the appropriate chart in .
  3. Turn the ignition switch on. Verify that the Service Engine Soon light is on.
  5. Install the scan tool and check the following:

Throttle Position Sensor (tps)-if over 2.5 volts, at closed throttle, check the tps and circuit.

Coolant Sensor-if not between -30°C and 130dgC, checks the coolant temperature sensor and circuit.

  1. Disconnect all injector connectors and install injector test light (J-34730-2 or equivalent) in injector harness connector. Test light should be off.

Perform this test on 1 injector from each bank.

  1. Connect spark checker, (J-26792 or equivalent), and check for spark while cranking. Check at least 2 wires.
    1. If spark occurs, reconnect the spark plug wires and check for fuel spray at the injector(s) while cranking.
    3. If no spark occurs, check for battery voltage to the ignition system through the ign fuse. If ok, substitute known good parts for possible faulty ignition parts. If this is not feasible, refer to the `C-4" charts for your engine application in .