Initial Inspection and Diagnostic Overview
How DTCs P1350/P1361 are SetThe IC output circuitry in the PCM issues 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 its own IC output, and expects to see no pulses on the IC circuit when it has not yet applied 5 volts on the bypass control circuit. When the second 3X reference pulse at the start of crank is seen by the PCM, it applies 5 volts to the bypass control circuit and the IC pulses should no longer be grounded by the ignition control module. The PCM constantly monitors its IC output, and should detect the IC pulses only when commanding the IC Mode.
If the IC circuit is open, the PCM will detect IC output pulses while attempting to start the engine (in the Bypass Mode) due to the ignition control module not being able to ground the IC pulses. Three things will occur:
^ DTC P1350 will set.
^ The PCM will not apply 5 volts to the bypass circuit.
^ The engine will start and run in Bypass Mode.
If IC circuit is grounded, the PCM would not detect a problem until the change to IC Mode is commanded by the PCM. When the PCM applies 5 volts to the bypass control circuit, the ignition control module will switch to IC Mode. With the IC circuit grounded, there would be no IC pulses for the ignition control module to trigger the ignition coils, and the engine may falter. The PCM will quickly revert back to Bypass Mode (turn Off the 5 volts on the bypass circuit), DTC P1361 will set, and the ignition system will operate in Bypass Mode until the fault is corrected and the engine is stopped and restarted. If bypass circuit is open or grounded, the ignition control module cannot not switch to IC Mode. In this case, the IC pulses will stay grounded in the ignition control module, and DTC P1361 will be set. The engine will start and run in Bypass Mode.
Results of Incorrect Operation
An open or ground in the IC or bypass circuit will set DTC P1350 or P1361. If a fault occurs in the IC output circuit when the engine is running, the engine may falter or quit running but will restart and run in the Bypass Mode once the ignition has been cycled. A fault in either circuit will force the ignition system to operate on Bypass Mode timing (10 degrees BTDC), which will result in reduced performance and fuel economy.
The PCM uses information from the engine coolant temperature sensor in addition to RPM to calculate spark advance values as follows:
^ High RPM = more advance
^ Cold engine = more advance
^ Low RPM = less advance
^ Hot engine = less advance Therefore, detonation could be caused by high resistance in the engine coolant temperature sensor circuit. Poor performance could be caused by low resistance in the engine coolant temperature sensor circuit.
If the engine cranks but will not run or immediately stalls, Engine Cranks But Will Not Run diagnostic table must be used to determine if the failure is in the ignition system or the fuel system. If DTC P0300, P0321, P0341, P0336 P1200, P1350 P1361 or P1374 is set, the appropriate diagnostic trouble code chart must be used for diagnosis. If a misfire is being experienced with no DTC set, refer to Symptoms for diagnosis. Testing and Inspection