For 1990-2009 cars

Refer to

#### Ignition System

Engine Controls Components
Fuel Injector Control
MIL Lamp, Voltage and Grounds, Serial Data
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice
.

### 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 1200 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 3 X 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 Setting the DTC

• | The engine is running (3X reference pulses are being received).

• | The ratio of 24X reference pulses to 3X reference pulses received by the PCM does not equal 8.

• | The ratio of 3X reference pulses to CAM signal pulses received by the PCM equals 6.

• | Above conditions for 30 seconds.

### Action Taken When the DTC Sets

• | The PCM will illuminate the MIL during the second key cycle in which the DTC sets.

• | The PCM will use the 3X reference signal circuit for fuel and ignition control.

• | The PCM will store conditions which were present when the DTC set as Freeze Frame and Fail Records data.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF on the third consecutive trip cycle during which the diagnostic has been run and the fault condition is no longer present.

• | A history DTC P0336 will clear after 40 consecutive warm-up cycles have occurred without a fault.

• | DTC P0336 can be cleared by using the scan tool Clear Info function or by disconnecting the PCM battery feed.

### 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.

• | 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.

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

Number(s) below refer to the step number(s) on the Diagnostic Table.

1. 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 | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Attempt to start engine. Does engine start? | -- | Go to Step 3 | Go to Engine Cranks but Does Not Run
3 |

1. Clear DTC P0336.
2. Start the engine and idle for 1 minute.
3. Observe DTC(s).

Is DTC P0336 set?

--

Go to Step 4

Refer to Diagnostic Aids

4 |

1. Turn OFF the ignition switch.
2. Disconnect the PCM connector C1.
3. Connect a fused jumper between B+ and the 24X/Cam sensor feed circuit.
4. Connect J 39200 digital multimeter between the 24X signal circuit and ground.

Does the DVM display a voltage near the specified value?

B+

Go to Step 5

Go to Step 7

5 |

1. Remove the fuel injector fuse.
2. Leave the fused jumper between B+ and the 24X/Cam sensor feed circuit.
3. Connect a jumper between the 24X/cam sensor ground and engine ground.
4. Leave the DVM connected to the 24X signal circuit.
5. Observe the DVM while cranking the engine.

Does the DVM display a voltage near the specified value?

B+

Go to Step 6

Go to Step 8

6 |

1. Check for the following circuit conditions:

• | 24X signal circuit shorted to voltage or the 24X sensor feed.

• | An open in the 24X sensor ground circuit (between the splice and the 24X sensor).

• | A faulty splice connection in the 24X/cam sensor ground circuit.

• | Poor terminal connection in the 24X sensor harness connector.

2. If a problem is found, repair as necessary. Refer to Repair Procedures in electrical Diagnosis.

Was a problem found?

Go to Step 11

Go to Step 9

7 |

1. Check for the following circuit conditions:

• | An open in the 24X CKP sensor feed (between the splice and the 24X sensor)

• | A faulty splice connection in the 24X/cam sensor feed circuit.

• | An open or short to ground/short to sensor ground in the 24X CKP sensor signal circuit.

• | Poor terminal connection in the 24X CKP harness connector.

2. If a problem is found, repair as necessary. Refer to Repair Procedures in Electrical Diagnosis.

Was a problem found?

--

Go to Step 11

Go to Step 9

8 | Check connections at the PCM and replace terminals if necessary. Refer to Repair Procedures in Electrical Diagnosis. Did any terminals require replacement? | -- | Go to Step 11 | Go to Step 10
9 |

1. Replace the 24X CKP sensor. Refer to Crankshaft Position Sensor Replacement .
2. Is action complete?

--

Go to Step 11

--

10 | Replace the PCM. Important: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Is action complete? | -- | Go to Step 11 | --
11 |

1. Review and record scan tool Fail Records data.
2. Clear DTCs.
3. Operate vehicle within Fail Records conditions as noted.
4. Using a scan tool, monitor SPECIFIC DTC info for DTC P0336 until the DTC P0336 test runs.

Note test result; does scan tool indicate DTC P0336 failed this ign?

--

Go to Step 2

System OK