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

Diagnosis and Testing

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SERVICE PRECAUTIONS




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

To avoid damage to the computer control module 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 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.
 
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.
 
Leave new components and modules in the shipping package until ready to install them.
 
Never disconnect any electrical connection with the ignition switch ON unless instructed to do so in a test.
 

SYMPTOM DIAGNOSIS



See Figure 1 through 10

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
  2.  
  3. Cold engine - more spark advance
  4.  
  5. High MAP output voltage - less spark advance
  6.  
  7. Hot engine - less spark advance
  8.  

Therefore, briefly, 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, as described in Driveability & Emissions Controls . If codes, exist, refer to the corresponding diagnostic charts in Chapter 4 . Otherwise, the following charts may be helpful.



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Fig. Fig. 1: Ignition system circuits-2.2L engine



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Fig. Fig. 2: Ignition system diagnosis-2.2L engine



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Fig. Fig. 3: Ignition system circuits-2.5L engine



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Fig. Fig. 4: Ignition system diagnosis-2.5L engine



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Fig. Fig. 5: Ignition system circuits-2.8L engine



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Fig. Fig. 6: Ignition system diagnosis-2.8L engine



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Fig. Fig. 7: Ignition system circuits-3.1L engine



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Fig. Fig. 8: Ignition system diagnosis-3.1L engine



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Fig. Fig. 9: Ignition system circuits-3.4L engine



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Fig. Fig. 10: Ignition system diagnosis-3.4L engine

 
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