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DTC P023:

Ignition Module Circuit:

CIRCUIT DESCRIPTION:
For complete description of how ignition spark is controlled by the PCM and Ignition Control Module, refer to Ignition System. Code P023 will set under either of the two following conditions:

1. 4X reference pulses are being received by the PCM and the bypass line is low, and the PCM detects pulses on the ignition control line. This could be caused by the bypass line shorted to voltage, or a faulty ignition control module.
2. 4X reference pulses are being received by the PCM and the bypass line is high, and the PCM does NOT detect a signal on the ignition control line. This could be caused by an open or a shorted to ground ignition control line or bypass line open or shorted to ground.

TEST CONDITION #1 CRANK:
1. Code P035 is not set.
2. Bypass line low (0 volt).
3. At least two 4X reference pulses have been received by the PCM;
OR
Test #2 failed previously this ignition cycle.

TEST CONDITION #2 RUN:
1. Code P035 is not set.
2. Bypass line High (5 volts).
3. At least two 4X reference pulses have been received by the PCM.

FAILURE CONDITION #1 CRANK:
Ignition control pulses detected on CKT 423 in bypass;
OR
Test #2 failed previously this ignition cycle.

FAILURE CONDITION #2 RUN:
No ignition control pulses detected on CKT 423.

ACTION TAKEN:
1. PCM turns 'ON' 'SERVICE ENGINE SOON' MIL.
2. PCM-controlled spark is disabled for ignition cycle.
3. PCM disables EGR.
4. Transaxle shift adapts are maintained at current levels.

NOTES ON FAULT TREE:
1. Check if Code P035 is set because a REF LO problem can cause other ignition problems.
2. Checking to see if Code P023 was set during "CRANK" or while engine was running.
3. Checking if there is a short to voltage on CKT 424 or if a PCM failure is causing the ignition control system to be in bypass spark control when it should not be.
4. Checking to see if there is an open in CKT 423 that is causing no ignition control pulses to reach the ignition control module or if pulses are reaching the ignition control module and it is doing nothing with them.
5. Checking for a short to voltage on CKT 424.