Refer to Engine Controls Schematics
Cell 21: Ignition System, Knock Sensors
Circuit Description
The ignition control module (ICM) produces an 18X reference signal. The ICM calculates the 18X reference signal by filtering the crankshaft position (CKP) sensor 18X pulses when the engine is running and when CKP sync pulses are also being received. The powertrain control module (PCM) uses the 18X reference signal in order to calculate the engine RPM and the crankshaft position at engine speeds below 1200 RPM. The PCM constantly monitors the number of pulses on the 18X reference circuit and compares the number of 18X reference pulses to the number of 3X reference pulses and to the CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 18X reference circuit, the PCM will use the 3X reference signal circuit for fuel and ignition control. The engine will continue to start and run using only the 3X reference and the CAM signals. DTC P0336 will set.
Conditions for Running the DTC
The engine is running and the 3X reference pulses are being received.
Conditions for Setting the DTC
| • | The ratio of 18X reference pulses to 3X reference pulses received by the PCM does not equal 6:1. |
| • | The ratio of 3X reference pulses to CAM signal pulses received by the PCM equals 6:1. |
| • | The conditions are present for more than 10 seconds. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the malfunction indicator lamp (MIL) during the second consecutive trip in which the diagnostic test has been run and failed. |
| • | The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data. |
Conditions for Clearing the MIL/DTC
| • | The PCM will turn OFF the malfunction indicator lamp (MIL) during the third consecutive trip in which the diagnostic has run and passed. |
| • | The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction. |
| • | The DTC can be cleared by using a scan tool. |
Diagnostic Aids
An intermittent may be caused by a poor connection, by rubbed through wire insulation, or by a broken wire inside the insulation. Inspect for the following conditions:
| • | A misrouted wiring harness--Ensure that the ICM harness is not routed near secondary ignition components. |
| • | A malfunctioning ignition coil--Remove the ignition coils and inspect the ignition control module and coils for cracks, for carbon tracking, or for other signs that indicate that the coil secondary circuit is arcing to the ICM or to the ICM wiring harness. Refer to Ignition Coil Replacement . |
| • | The secondary ignition wires arcing to wiring harness--Inspect secondary ignition wires for carbon tracking or for other signs of damage. |
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.
Step | Action | Values | Yes | No | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||||||||||
1 | Did you perform the Powertrain On-Board (OBD) system check? | -- | Go to Step 2 | |||||||||
2 | Attempt to start the engine. Does the engine start and run? | -- | Go to Step 3 | Go to Step 8 | ||||||||
3 | Observe the 18X Crank Sensor parameter with the scan tool. Does the 18X Crank Sensor parameter change with engine speed? | -- | Go to Step 4 | Go to Step 5 | ||||||||
4 |
Does the DTC fail this ignition? | -- | Go to Step 5 | Go to Testing for Intermittent Conditions and Poor Connections | ||||||||
5 |
Does the test lamp illuminate? | -- | Go to Step 10 | Go to Step 6 | ||||||||
6 |
Does the test lamp illuminate? | -- | Go to Step 9 | Go to Step 7 | ||||||||
7 |
Does the 18X Crank Sensor change? | -- | Go to Step 13 | Go to Step 11 | ||||||||
8 |
Is the voltage within the specified range? | 4-8 V | Go to Step 14 | Go to Step 12 | ||||||||
9 | Test the 18X reference medium resolution engine speed signal circuit between the ICM and the powertrain control module (PCM) for a short to ground. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||||
10 | Test the 18X reference medium resolution engine speed signal circuit between the ICM and the PCM for a short to voltage. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||||
11 | Test the 18X reference medium resolution engine speed signal circuit between the ICM and the PCM for an open. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 16 | ||||||||
12 | Test the CKP sync signal circuit for an open. Refer to Wiring Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 15 | ||||||||
13 | Inspect for the following conditions:
Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 15 | ||||||||
14 | Test for an intermittent or for poor connections at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 17 | ||||||||
15 | Test for an intermittent or for poor connections at the ICM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 18 | ||||||||
16 | Test for poor connections at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs . Did you find and correct the condition? | -- | Go to Step 20 | Go to Step 19 | ||||||||
17 | Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||
18 | Replace the ICM. Refer to Ignition Control Module Replacement . Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||
19 | Replace the PCM. Refer to Powertrain Control Module Replacement/Programming for replacement, setup, and programming. Did you complete the replacement? | -- | Go to Step 20 | -- | ||||||||
20 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 21 | ||||||||
21 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | |||||||||
