Circuit Description
The ignition system uses a waste spark method of spark distribution. During cranking, the ignition control module (ICM) monitors the crankshaft position sensor signals. The signals are used to determine the correct pair to spark first. After the crankshaft position signals have been processed by the ICM, it sends a fuel control reference pulse to the powertrain control module (PCM). When the PCM receives this pulse it will command all eight injectors to open for a priming shot of fuel in all cylinders. After priming, the injectors are left OFF for the next eight fuel control reference pulses from the ICM (two crankshaft revolutions). This allows each cylinder a chance to use the fuel from the priming shot. During this waiting period, a cam pulse will have been received by the PCM. Now the PCM begins to operate the injectors sequentially based on true crankshaft position. However, if the cam signal is not present at start-up, DTC P0340 will set and the PCM will start fuel delivery in a random pattern with a 1 in 8 chance that fuel delivery is correct.
The crankshaft position sensor signals are used only by the IC module. It is used for spark synchronization and to initiate reference pulses only (not passed to the PCM).
Diagnostic Aids
Perform the Powertrain On Board Diagnostic (OBD) System Check before performing this chart to help prevent mis-diagnosis.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you performed the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | |
2 | Are DTCs P0230, P0322, P0601, P0602 or P1631 set? | -- | Go to DTCs that are set | Go to Step 3 |
3 |
Does the spark tester indicate a crisp blue spark on all tested cylinders? | -- | Go to Step 4 | Go to Ignition System Diagnosis |
4 |
Was fuel pump operation heard? | Go to Step 5 | ||
5 |
Do both injectors blink on and off? | -- | Go to Step 9 | Go to Step 6 |
6 |
Is the voltage at or above the specified value for both injectors? | 10V | Go to Step 8 | Go to Step 7 |
7 | Repair the open or short to ground in the ignition feed circuit that did not illuminate the test lamp. Is repair complete? | -- | Go to Step 10 | -- |
8 |
Important: The replacement PCM must be programmed. Replace PCM. Refer to Powertrain Control Module Replacement/Programming . Is the replacement complete? | -- | Go to Step 10 | -- |
9 | Perform the fuel system diagnosis. Refer to Fuel System Diagnosis . Was a repair made to the vehicle in the fuel system diagnosis? | -- | Go to Step 10 | Go to Step 11 |
10 | Does the vehicle now start and run? | -- | Go to Step 11 | |
11 | Check for a mechanical condition that could cause a no start condition, for example a broken timing chain. Was a mechanical repair made? | -- | System OK |
