For 1990-2009 cars

Refer to

#### Cell 21: Ignition Controls

Engine Controls Component Views
Information Sensors/Switches Description
Cell 21: Fuel Controls
Cell 21: Power, Ground, MIL, and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Ground Distribution Schematics

### Circuit Description

The 24X reference signal is used to improve idle spark control at low engine speeds. The PCM uses the 24X reference signal to calculate engine RPM and crankshaft position at engine speeds below 1600 RPM. The PCM constantly monitors the number of pulses on the 24X reference circuit and compares the number of 24X reference pulses to the number of 3X reference pulses and CAM signal pulses being received. If the PCM receives an incorrect number of pulses on the 24X 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) for a minimum of 3 seconds.

### Conditions for Setting the DTC

The ratio of 24X reference pulses to 3X reference pulses received by the PCM is incorrect.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure.

• | The PCM writes the conditions to the Freeze Frame and updates the Failure Records.

### 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

DTC P0336 can be caused by secondary components leaking high voltage into the ignition module. Check for the following conditions:

• | Incorrect harness routing near secondary ignition components.

• | Ignition coil arcing to wiring harness or Ignition Control Module (check ignition coils for cracks, carbon tracking, or other signs of damage).

• | Secondary ignition wire(s) arcing to wiring harness.

An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation. Check for:

• | Poor connection. Inspect the PCM harness and connectors for improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection. Refer to Intermittents and Poor Connections Diagnosis Repairing Connector Terminals and Connector Repairs .

• | 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 24X reference circuit at the PCM harness connector while moving connectors and wiring harnesses related to the 24X Crankshaft Position Sensor and Camshaft Position Sensor. The 24X and Camshaft Position sensors share the same sensor feed from the PCM. A change in voltage will indicate the location of the fault. Refer to Wiring Repairs .

It also may be helpful to monitor the 24X RPM on the scan tool, to look for erratic RPM fluctuations.

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.

### Test Description

The numbers below refer to the step numbers on the diagnostic table:

1. If sent here from DTC P0327 proceed with DTC P0336 Diagnostic even if P0336 has not failed this ignition.

2. The 24X RPM on the scan tool should change each time the signal circuit is touched.

3. If the fuse blows in the jumper wire, there is a short to ground on the signal circuit.

4. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.

#### DTC P0336 - 24X Reference Signal Circuit

Step | Action | Values | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain OBD System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 |

1. Turn the ignition on.
2. Review and record scan tool fail records data.
3. Operate vehicle within fail records condition as noted.
4. Using a scan tool, monitor specific DTC info for DTC P0336 until DTC P0336 test runs.

Does scan tool indicate DTC P0336 failed this ignition?

--

Go To Step 3

Go To Diagnostic Aids

3 | Using the scan tool monitor 24X RPM. Does 24X RPM vary with engine speed up to approximately 1600 RPM? | -- | Go To Diagnostic Aids | Go To Step 4
4 |

1. Turn the ignition OFF.
2. Disconnect the 24X CKP sensor connector.
3. Turn ON the ignition, with the engine OFF.
4. Using DMM, check for voltage at 24X sensor feed circuit.

Does DMM display a voltage near the specified value?

B+

Go To Step 6

Go To Step 5

5 |

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Check for an open or short to ground in the 24X CKP sensor feed circuit, repair as necessary. Refer to Wiring Repairs .

Was a problem found?

--

Go To Step 16

Go To Step 12

6 |

1. Connect an test lamp to battery positive voltage.
2. Touch 24X CKP sensor ground circuit.

Does test lamp illuminate?

--

Go To Step 8

Go To Step 7

7 |

1. Turn the ignition OFF.
2. Disconnect the PCM.
3. Check for an open in the 24X CKP sensor ground, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a problem found?

--

Go To Step 16

Go To Step 12

8 |

1. Monitor 24X RPM on the scan tool.
2. Using a 5 amp fused jumper wire connected to battery positive voltage momentarily touch the signal circuit 5 times for a duration of 1 second each.

Does 24X RPM change EACH time the signal circuit is touched?

--

Go To Step 14

Go To Step 9

9 | Did the fuse in the jumper wire blow? | -- | Go To Step 11 | Go To Step 10
10 | Check signal circuit for an open or a short to voltage, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found? | -- | Go To Step 16 | Go To Step 12
11 | Check signal circuit for a short to ground, repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a problem found? | -- | Go To Step 16 | Go To Step 12
12 | Check for poor connections at PCM and replace terminals as necessary. Refer to Testing for Continuity , Intermittents and Poor Connections Diagnosis , Repairing Connector Terminals , and Connector Repairs . Did any terminals require replacement? | -- | Go To Step 16 | Go To Step 13
13 | Important: : Replacement PCM must be reprogrammed. Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | Go To Step 16 | --
14 | Check for poor connections at 24X CKP sensor and replace terminals as necessary. Refer to Testing for Continuity , Wiring Repairs , Repairing Connector Terminals , and Connector Repairs in Wiring Systems. Did any terminals require replacement? | -- | Go To Step 16 | Go To Step 15
15 | Replace 24X CKP sensor. Refer to Crankshaft Position Sensor Replacement . Is the action complete? | -- | Go to Step 16 | --
16 |

1. Review and record fail records data.
2. Clear DTCs.
3. Operate vehicle within fail records parameters as noted.
4. Using scan tool monitor Specific DTC for DTC P0336 until the DTC P0336 test runs.

Does scan tool indicate DTC P0336 failed this ignition?

--

Go To Step 2

System OK