Circuit Description
The ignition system uses a waste spark method of spark distribution. During cranking, the Ignition Control (IC) module 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 IC module, it sends a fuel control reference pulse to the 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 IC module (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 Powertain OBD System Check before performing this table to help prevent mis-diagnosis.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Powertrain On-Board Diagnostic System Check? | -- | ||
2 | Are DTC(s) P0231, P0232, P0322, P0601, P0602, P1376, P1631, P1632 OR P1634 set? | -- | Go to DTCs that are set. | |
3 |
Does the spark tester indicate a crisp blue spark on all tested cylinders? | -- | Go to Electronic Ignition System Diagnosis - Ignition System Check | |
4 |
Was fuel pump operation heard? | |||
5 | Perform the PCM Power And Ground Check and the Powertrain Ground Check. Refer to Powertrain Control Power and Ground Check . Was a repair to the vehicle made in either table? | -- | ||
6 |
Do both injectors blink on and off? | -- | ||
7 |
Is the voltage the same or higher than the value specifed on both terminals? | 10 volts | ||
8 | Repair the injector ignition feed circuit(s) between C127 and fuse(s). Is repair complete? | -- | -- | |
9 | Replace PCM. Refer to Powertrain Control Module Replacement/Programming Is the replacement complete? | -- | -- | |
10 | Perform Fuel System Diagnosis. Refer to Fuel System Diagnosis . Was a repair made to the vehicle in the Fuel System Diagnosis? | -- | ||
11 | Does the vehicle now start and run? | -- | ||
12 | Check for a mechanical condition that could cause a no start condition, for example a broken timing chain. Was a mechanical repair made? | -- | Go to Powertrain Control Module Diagnosis for Verify Repair |
