ALLDATA Online - 1993 Pontiac Bonneville V6-3800 3.8L - Chart A-3 Engine Cranks.

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Vehicle Level Powertrain Management Computers and Control Systems Testing and Inspection Diagnostic Trouble Code Tests and Associated Procedures Related Tests and Information A Charts Chart A-3 Engine Cranks But Will Not Run
Chart A-3 Engine Cranks But Will Not Run
Ignition System Circuit Diagram (Type II)

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CIRCUIT DESCRIPTION : The C3I ignition system uses a waste spark method of spark distribution. There are 3 ignition coils, each firing two cylinders at once. One cylinder is on the compression cycle, while the other is on the exhaust cycle. The ignition module triggers the correct coil, based on signals from the crankshaft sensor. During cranking, the ignition module monitors the dual crank sensor sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal has been processed by the ignition module, it sends a fuel control reference pulse to the PCM. When the PCM receives this pulse, it will command all six injectors to open for one shot of fuel in all cylinders. After the priming, the
http://alldatapro.com/alldata/PRO~V153345179~C19748~R0~OD~N/0/41746052/42417. 10/12/2010

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injectors are left off for the next six fuel control reference pulses from the ignition module. This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, a cam pulse will have been received by the PCM. Now the PCM begins to operate the injectors sequentially, based on true camshaft position. However, if the cam signal is not present at start-up a Code 41 will set and the PCM will start sequential fuel delivery in any old random pattern. There is a 1 chance in 6 that fuel delivery will be correct. The sync signal is used only by the ignition module, for spark synchronization at start-up only. TEST DESCRIPTION Chart A-3, Engine Cranks but Won't Run (1 Of 3)

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PART 1 OF 3 Numbers below refer to circled numbers on the diagnostic chart. 1. A blinking injector test light verifies that the PCM is monitoring the fuel control signal and attempting to activate the injectors.

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2. The crank sensor has been verified as functioning properly, as is evident by the blinking injector test light. A fuel pressure test at this point will separate the diagnostic path into either a fuel related fault or ignition system malfunction. 3. By testing for spark on plug leads 1, 3, and 5, each ignition coil's ability to produce at least 25,000 volts is verified. 4. By testing the problem coil's control circuit with a test light, a determination can be made as to the problem coil being faulty or the module's internal driver for that coil being the source of the complaint. Chart A-3, Engine Cranks but Won't Run (2 Of 3)

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PART 2 OF 3 5. Tests for battery voltage on CKT 1039. If voltage was present, the "light OFF" test result was caused by no activation pulse reaching the injector connector from the PCM.

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Chart A-3, Engine Cranks but Won't Run (3 Of 3)
PART 3 OF 3 6. The test light to 12 volts simulates a reference signal to the PCM which will result in an injector test light blink with each touch of the test light to terminal "D". It may take up to three touches to get an injector test light flash. CKT

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430, the PCM, and the injector driver circuits are all OK. Disconnect all injector connectors to avoid "flooding" the engine during testing. 7. Checks circuits 644, 645, 646 and the 3X portion of the crankshaft sensor. If circuit 646 has been shorted to power, make sure the crankshaft sensor has not been damaged. 8. Checks circuit 643 and the 18X portion of the crankshaft sensor. If circuit 646 has been shorted to power, make sure the crankshaft sensor has not been damaged. 9. Verifies that battery power is supplied to the ignition module and coils (circuit 839) when the ignition is turned "ON".
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