Refer to
IC Module, CMP and CKP Sensors
in Engine Controls Schematics.
Circuit Description
The 18X reference signal is produced by the ignition control module. The PCM uses the 18X reference signal to calculate engine RPM and 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 3 X reference pulses and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 18X reference circuit, DTC P0336 will set and the PCM will use the 3X reference signal circuit for fuel and ignition control. The engine will continue to start and run using the 3X reference and CAM signals only.
Conditions for Running the DTC
The engine is running (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 to 1. |
| • | The ratio of 3X reference pulses to CAM signal pulses received by the PCM equals 6 to 1. |
| • | The above conditions are present for 290 of 300 test samples. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test runs and fails. |
| • | The PCM will store the conditions that were present when the DTC set as Freeze Frame and Fail Records data. |
Action Taken When the DTC Sets
| • | The PCM will illuminate the MIL during the second consecutive trip in which the diagnostic test runs and fails. |
| • | The PCM will use the 3X reference signal circuit for fuel and ignition control. |
| • | If equipped with traction control, the PCM will command the electronic brake and traction control module (EBTCM) via the Class 2 Serial Data to set an antilock brake system (ABS) / traction control system (TCS) DTC. Then, EBTCM will turn OFF the traction control, and the TRACTION OFF lamp will illuminate. |
| • | The PCM will store the conditions present when the DTC set as Freeze Frame and Fail Records data. |
Diagnostic Aids
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check the following components and conditions:
| • | A faulty connection--Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Use a corresponding mating terminal to check for proper terminal tension. |
| • | A damaged harness--Inspect the wiring harness for damage. If the harness appears to be OK, disconnect the PCM, turn the ignition on and observe a voltmeter connected to the 18X reference circuit at the PCM harness connector while moving connectors and wiring harnesses related to the ignition control module (ICM). A change in voltage will indicate the location of the malfunction. |
| • | A misrouted wiring harness--Inspect the ICM harness to ensure that it is not routed near the secondary ignition components |
| • | A malfunctioning ignition coil--Remove the ignition coils and inspect the ignition control module and coils for cracks, carbon tracking, or other signs that indicate that the coil secondary circuit is arcing to the ICM or ICM wiring harness. Refer to Ignition Coil Replacement . |
| • | Secondary ignition wires arcing to the wiring harness--Check secondary ignition wires for carbon tracking or other signs of damage. |
Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.
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 | |||||||||
