Diagnosis

If the 18X reference signal is not received by the PCM while the engine is running, a DTC P0336 is set, the 3X reference is used to control spark advance under 1200 RPM, and Bypass Mode is in effect at engine speeds under 400 RPM. The engine continues to run and start normally.

If the 3X reference signal is not received by the PCM while the engine is running, the PCM uses the 18X reference pulses to calculate RPM and the crankshaft position. The engine continues to run and start normally, but DTC P1374 is set.

If an open reference low circuit occurs, reduced engine performance may result and possibly a MIL with no DTC.

The PCM generates IC timing pulses anytime crankshaft reference signals are being received. The PCM uses the IC control circuit to send the IC timing pulses to the Ignition Control Module (ICM). When the ignition system is operating in the Bypass Mode (no voltage on the bypass control circuit), the ICM grounds the IC pulses. The ignition system switches to the IC Mode when the PCM applies the 5 volt bypass signal to the ICM on the bypass circuit. The ICM switches the IC pulses from ground in order to allow the PCM to control the spark timing. The PCM monitors the IC and bypass circuits for electrical malfunctions affecting proper ignition system operation. If a malfunction occurs, diagnosis is included in the DTC P1351, P1352, P1361, and P1362 diagnostic tables. If diagnostic trouble codes are encountered, go to the DTC tables for diagnosis.

The following information lists important considerations to aid the technician in servicing the ignition system.
^ The ignition coil's secondary voltage output capabilities are very high - more than 40000 volts. Avoid body contact with the high voltage secondary ignition components when the engine is running, or personal injury may result.
^ The dual Hall-effect Crankshaft Position (CKP) Sensor is the most critical part of the ignition system. If the sensor is damaged so that the CKP 18X or CKP sync crank sensor pulses are not generated, the engine does not start.
^ There are 4 circuit wires connecting the dual CKP sensor to the ignition control module. If there is a problem with any of the 4 circuit wires, the engine does not start (no spark and no injector pulses). The circuits are described as follows:
- The 10 to 12 volt sensor feed for the Hall effect switches from the ignition control module.
- The 18X CKP pulse signal to the ignition control module.
- The CKP sync pulse signal to the ignition control module.
- The sensor ground circuit for both Hall-effect switches.
^ If the CKP sync pulses stop while the engine is running, the engine keeps running. The ignition control module remembers the correct ignition coil sequence. However, the engine does not restart after being shut off.
^ If the 18X CKP pulses stop while the engine is running, the engine stops running and does not restart. The loss of the 18X CKP signal to the ICM results in the loss of CKP information and the ICM's ability to generate the 3X reference signals.
^ The CKP sensor clearance is very important. The sensor MUST NOT contact the rotating interrupter rings at any time, or sensor damage results. If the balancer interrupter rings are bent, the interrupter ring blades can destroy the sensor.
^ The ignition timing is not adjustable. There are no timing marks on the crankshaft balancer or timing chain cover.
^ If CKP sensor replacement is necessary, the crankshaft balancer must be removed first. The balancer is a press fit onto the crankshaft. Removing the serpentine accessory drive belt and balancer attaching bolt allows Balancer removal with the J 38197 balancer remover.
^ When reinstalling the crankshaft balancer, torque the balancer attachment bolt to the proper specifications. This is critical in order to prevent crankshaft damage and to ensure that the balancer stays attached to the crankshaft.
^ If a CKP sensor assembly is replaced, inspect the crankshaft balancer interrupter rings for bent blades. If a bent blade exists, the new CKP sensor may be destroyed within a single crankshaft revolution.
^ Neither side of the ignition coil primary or secondary windings is connected to engine ground. Although the ignition coil packs are secured to the ignition control module, this is not an electrical connection to ground.
^ Be careful not to damage the secondary ignition wires or boots when servicing the ignition system. Do not pull on the ignition wire(s) without rotating each boot to dislodge the boot from the plug or coil tower. NEVER pierce a secondary ignition wire or boot for any purpose. Future problems with the wire are certain if pinpoints or testlamps are pushed through the insulation for testing.
^ The ignition control module is grounded to the engine block through a ground wire to the bracket mounting stud of the ignition control module. If service is required, ensure that good electrical contact is made between the ground and the mounting bracket, including the proper hardware and torque.
^ A conventional tachometer used to measure RPM on a primary ignition tach lead does not work on this ignition system. To measure RPM, use either of the following items:
- A tachometer designed with an inductive pickup, used on the secondary side of an ignition system. These tachometers are identified by a clamp that goes around a spark plug wire. Set the tachometer to 2-cycle operation. The 2-cycle setting is required because spark plugs on this engine fire every time the piston is at the top of a stroke. If a 2 cycle selection is not available, divide the indicated 4 cycle reading by 2.
- A scan tool.