P023

DTC PO23: Part 1 Of 2:

DTC PO23: Part 2 Of 2:

Distributor Circuit:

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

1. 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 at the distributor.

2. 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. Bypass line low (0 volt).

2. At least two reference pulses have been received by the PCM
OR
Test # 2 failed previously this ignition cycle.

TEST CONDITION # 2 RUN
1. Bypass line high (5 volts).
2. At least two 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" the "Service Engine Soon" Malfunction Indicator Lamp (MIL).
2. PCM - controlled spark is disabled for ignition cycle.
3. PCM disables Exhaust Gas Recirculation (EGR) solenoid.

NOTES ON FAULT TREE
Part 1 of 2
1. When CKT 423 is shorted to ground, the engine will have a long crank and hard start. When the PCM detects the grounded circuit, the bypass line will be shifted LO.

2. With only Distributor reference and Distributor reference ground jumpered to the PCM, the engine will run on backup spark. Checking for proper ground connection between PCM and the engine and the PCM and ICM.

3. Checking for PCM providing an ignition control output on CKT 423.

4. Checking for Ignition Control Module able to ground ignition control signal with open Bypass circuit.

Part 2 of 2
5. Checking for ignition control module able to recognize a voltage on the Bypass circuit and to stop grounding ignition control (PCM controlled timing).

6. Checking for Bypass signal to the module. If Bypass is being sent by the PCM to the ignition control and if the module is interpreting Bypass voltage correctly, then the module will switch off the ground to the ignition control.

7. If the chart leads to "Ignition Control Circuit is OK," then a fault may exist in the 6-way Weatherpack connector. Check for proper connector mating and for pins backing out of the Weatherpack connector. If no trouble is found with the connector, reconnect the 6-way connector, clear codes and retest.