Refer to Engine Controls Schematics . .
Circuit Description
The electronic ignition (EI) system uses a waste spark method of spark distribution. In this type of ignition system, the ignition control (IC) module triggers the correct coil based on the 3X signal received from the crankshaft position (CKP) 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 IC module monitors the CKP 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 IC module, it sends a 3X reference signal to the Powertrain Control Module (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 a 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 ICM. It is used for spark synchronization at start-up only (not passed to the PCM).
Diagnostic Aids
Inspect 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. |
| • | Faulty engine coolant temperature (ECT) sensor.--Using a scan tool, compare engine coolant temperature with intake air temperature on a completely cool engine. The engine coolant temperature should be within 10°C (50°F) of intake air temperature. If not, replace the ECT sensor. Refer to Engine Coolant Temperature Sensor Replacement . |
Many situations may lead to an intermittent condition. Perform each inspection or test as directed.
Important: : Remove any debris from the connector surfaces before servicing a component. Inspect the connector gaskets when diagnosing or replacing a component. Ensure that the gaskets are installed correctly. The gaskets prevent contaminate intrusion.
| • | Loose terminal connection |
| - | Use a corresponding mating terminal to test for proper tension. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| - | Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connection. Refer to Testing for Intermittent Conditions and Poor Connections , and to Connector Repairs in Wiring Systems for diagnosis and repair. |
| • | Damaged harness--Inspect the wiring harness for damage. If the harness inspection does not reveal a problem, observe the display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the scan tool display may indicate the location of the fault. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
| • | Inspect the powertrain control module (PCM) and the engine grounds for clean and secure connections. Refer to Wiring Repairs in Wiring Systems for diagnosis and repair. |
If the condition is determined to be intermittent, reviewing the Snapshot or Freeze Frame/Failure Records may be useful in determining when the DTC or condition was identified.
Test Description
The numbers below refer to the step numbers on the Diagnostic Table:
-
This step assumes that the starting system and battery voltage are not suspect.
-
Testing for spark at an ignition wire will determine if the problem is with the 7X crankshaft position sensor input to the IC Module. 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.
-
A blinking J 34730-380 Injector Load Tester LEDs verifies that the PCM is capable of activating the injectors.
A non-blinking J 34730-380 Injector Load Tester LEDs indicates a possible fault condition in the fuel injector circuits.
Step | Action | Values | Yes | No | ||||||||||||||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
1 | Did you perform the Powertrain On Board Diagnostic (OBD) System Check? | -- | ||||||||||||||||||||||||||||
2 |
Important: : If P0101, P0123, P0201-P0206, P0230, P0601-P0602, P1374, P1626, P1631 are stored diagnose those DTCs first.
Does the Fuel Pump run while being commanded on? | -- | ||||||||||||||||||||||||||||
3 |
Is the fuel pressure within the specified value? | 284-325 kPa (41-47 psi) | ||||||||||||||||||||||||||||
4 |
Does the scan tool indicate 3X reference signal present? | -- | ||||||||||||||||||||||||||||
Is there spark present? | -- | |||||||||||||||||||||||||||||
Does all of the LEDs for cylinders 1-6 flash? | -- | Go to Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Between 10-35 Degrees C (50-95 Degrees F) or Fuel Injector Solenoid Coil Test - Engine Coolant Temperature Outside 10-35 Degrees C (50-95 Degrees F) | ||||||||||||||||||||||||||||
7 | Inspect the engine for the following conditions:
Did you find and correct the condition? | -- |
