Engine Cranks But Does Not Run

Circuit Description
The Electronic Ignition system uses a waste spark method of spark distribution. In this type of ignition system, the Ignition Control module triggers the correct coil based on the 3X signal received from the Crankshaft Position sensor, resulting in both spark plugs connected to the coil firing at the same time. The spark plug for the cylinder on the exhaust stroke requires a lower energy requirement to fire, leaving the remaining high voltage to fire the spark plug for the cylinder on the compression stroke.

During cranking, the Ignition Control module monitors the Crankshaft Position sensor input for recognition of the sync signal. The sync signal is used to determine the correct cylinder pair to spark first. After the sync signal has been processed by the Ignition Control module, it sends a 3X reference signal to the PCM. When the PCM receives this signal it will command all six injectors to open for one priming shot of fuel in all cylinders. After the priming, the injectors are left off for the next six 3X reference signals from the Ignition Control module (two crankshaft revolutions). This allows each cylinder to use the fuel from the priming shot. During this waiting period, a cam signal will have been received by the PCM. After the true Camshaft Position is detected, the PCM operates the injectors sequentially. However, if the cam signal is not present at start-up, DTC P0341 Camshaft Position (CMP) Sensor Performance will set and the PCM will start sequential fuel delivery in random pattern with a 1 in 6 chance that fuel delivery is correct.

The sync signal is used only by the Ignition Control module. It is used for spark synchronization at start-up only (not passed to the PCM).

Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for the following items:
^ Mass Air Flow is compared to a calculated Mass Air Flow based upon the MAP, TP, and engine RPM readings (speed density). A Skewed/unresponsive MAP sensor at KEY on will cause the predicted air flow value to be inaccurate. Compare MAP and TP sensor to that of a normal operating system.
^ Poor connection or damaged harness. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness. Refer to Intermittents and Poor Connections. Symptom Related Diagnostic Procedures
^ Faulty Engine Coolant Temperature Sensor. Using a scan tool, compare Engine Coolant Temperature with Intake Air Temperature on a completely cool engine. Engine Coolant Temperature should be within 10°C of Intake Air Temperature. If not, replace the ECT sensor. Refer to ECT Sensor Replacement.
^ If the BCM is replaced, the PCM needs to be reflashed (refer to PCM Replacement/Programming) to allow the new BCM password to be learned into the PCM.

Test Description
The number(s) below refer to the step number(s) on the Diagnostic Table:
3. A skewed MAP sensor can cause the BARO reading to be incorrectly calculated. To test the MAP sensor, compare the MAP/BARO reading on the vehicle to the MAP/BARO reading on a normally operating vehicle. If there is a skewed or stuck map sensor vehicle may not start, compare the MAP reading with that of another vehicle.
4. This step checks the MAP sensor. By disconnecting the MAF sensor, the vehicle is forced into speed density: Speed density is based on the MAP, TP, and engine RPM readings. With a skewed/unresponsive MAP sensor, the speed density calculation is incorrect and vehicle may not start.
7. A blinking J 34730-2C Injector Test Light verifies that the PCM is capable of activating the injectors.
A non-blinking J 34730-2C Injector Test Light indicates a possible fault condition in the fuel injector circuits.
8. Checking for spark at an ignition wire will determine if the problem is with the 7X Crankshaft Position sensor input to the IC Module. A blinking injector J 34730-2C Injector Test Light with no spark suggests a fault condition in the ignition system. By using J 26792 Spark Tester to test for spark at the ignition coil towers each ignition coils ability to produce at least 25,000 volts is verified.
18. By testing the problem coils control circuit with a J 34730-2C Injector Test Light, a determination can be made as to the problem coil being faulty or the Ignition Control modules internal driver circuit for the affected coil being the cause of the complaint.
27. Before replacing the MAP sensor review Diagnostic Aids. Apply vacuum with hand held vacuum pump while monitoring scan tool, MAP reading should increment smoothly with each stroke of vacuum pump. Refer to MAP Sensor Circuit Test for MAP Sensor diagnosis. Component Tests and General Diagnostics