Diagnosis

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

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

Poor engine performance and possibly a MIL with no DTC can be caused If the Reference Low circuit is open or connected to ground at the PCM.

The IC output circuitry in the PCM generates IC output pulses anytime crankshaft reference signal input pulses are being received. When the ignition system is operating in the Bypass Mode (no voltage on the bypass control circuit), the ignition control module grounds the IC pulses coming from the PCM. The ignition control module will remove the ground from the IC circuit only after switching to the IC Mode.

The PCM commands switching to IC Mode by applying 5 volts on the bypass circuit to the ignition control module. The PCM monitors the IC and Bypass circuits for electrical malfunctions affecting proper ignition system operation. If a malfunction occurs, diagnosis is included in DTC P1351, P1352, P1361 and P1362 diagnostic tables. If diagnostic trouble codes are encountered, go to the DTC tables for diagnosis.

The following information will list important considerations to aid the technician in servicing the ignition system.
^ The ignition coils secondary voltage output capabilities are very high - more than 40000 volts. Avoid body contact with ignition high voltage secondary components when the engine is running, or personal injury may result!
^ The dual Hall-effect crankshaft position 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 will not start!
^ There are 4 circuit wires connecting the dual crankshaft position sensor to the ignition control module. If there is a problem with any of the four, the engine will 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 CKP 18X 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 will keep running. However, it will not restart after being shut OFF.
^ If the CKP 18X pulses stop while the engine is running, the engine will stop running and will not restart.
^ Crankshaft position sensor clearance is very important! The sensor must not contact the rotating interrupter rings at any time, or sensor damage will result. If the balancer interrupter rings are bent, the interrupter ring blades will destroy the sensor.
^ Ignition timing is not adjustable. There are no timing marks on the crankshaft balancer or timing chain cover.
^ If crankshaft position 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 will allow its removal with special tool J 38197.
^ When reinstalling, torque the balancer attachment bolt. This is critical to ensure the balancer stays attached to the crankshaft.
^ If a crankshaft position sensor assembly is replaced, check the crankshaft balancer interrupter rings for any blades being bent. It this is not checked closely and a bent blade exists, the new crankshaft position sensor can be destroyed by the bent blade with only one 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, it is not an electrical connection to ground.
^ Be careful not to damage the secondary ignition wires or boots when servicing the ignition system. Rotate each boot to dislodge it from the plug or coil tower before pulling it from either a spark plug or the ignition coil. Never pierce a secondary ignition wire or boot for any purpose! Future problems are guaranteed if pinpoints or test lights are pushed through the insulation for testing.
^ The ignition control module is grounded to the engine block through a ground wire to the ignition control module bracket mounting stud. If servicing is required, ensure that good electrical contact is made between the ground and the mounting bracket, including proper hardware and torque.
^ A conventional tachometer used to check RPM on a primary ignition tach lead will not work on this ignition system. To check RPM, use either of the following items:
- A tachometer designed with an inductive pickup, used on the secondary side of an ignition system. These tachs are identified by a clamp that goes around a spark plug wire. Set the tach 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 its stroke. If a 2 cycle selection is not available, divide the indicated 4 cycle reading by 2.
- A scan tool.