Powertrain Controls - ECM/PCM

Ignition Wiring Diagram:

CIRCUIT DESCRIPTION
The 3800 engine uses the simultaneous mode of fuel injection during start-up. As engine speed attains the 400 rpm level and a cam signal has been received by the Electronic Control Module (ECM) from the C3-I module, the fuel injection switches modes to sequential injection. This is accomplished by use of a cam interrupter magnet and a cam sensor "hall effect" switch.
The cam sensor sends a signal (sync-pulse) to the ignition module when cylinder # 1 is 25 degrees after top dead center on the compression stroke. This signal is used to start sequential fuel injection with the proper cylinder. If the cam signal is lost to the ECM, the engines fuel delivery will switch back to the simultaneous mode of operations. THE ENGINE WILL CONTINUE TO RUN. IT WILL RESTART AFTER SHUT DOWN.

Code 41 is set when the following condition is met: Engine is running and a cam sensor signal not received by ECM for last 2 seconds.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart:
1. Checks to see if ECM recognizes a problem and sets Code 41.
2. This step verifies proper operation of circuits 633, 644, and 645.
3. Step validates the integrity of circuit 630 from C3-I module to ECM.
4. If the camshaft gear magnet is interfacing with the cam sensor the voltage reading will be zero, bumping engine will cause the condition to go away.
5. If the voltage reading of "BC5" is constantly varying and connection to terminal "BC5" are good, the ECM is faulty.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check For
^ Poor connection or a damaged harness - Inspect ECM harness connectors for backed out terminal "BC5," improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

^ Intermittent test - If connections and harness check OK, monitor a digital voltmeter connected from ECM terminal "BC5" to ground while moving related connectors and wiring harness. If the failure is induced, the voltage reading will change. This may help to isolate the location of the malfunction.