For 1990-2009 cars
Engine Controls Components
Ignition System
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Crankshaft Position Sensor is mounted in the engine front cover assembly and works in conjunction with a 4X reluctor wheel on the front of the crankshaft. The CKP sensor has a B+ power supply, a ground and a signal circuit.

As the crankshaft rotates, the reluctor wheel teeth interrupt a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which is read by the PCM. The PCM uses this signal to accurately measure crankshaft velocity which is a variable used to detect misfire. This sensor is not used for spark or fueling. For this diagnostic the PCM monitors the Crankshaft Position Sensor signal, and the Low Resolution and the High Resolution signals from the distributor. During normal operation, at the falling edge of a Crankshaft Sensor signal pulse (signal voltage transitions to low), the PCM starts counting High Resolution pulses. The counter will increase until the PCM detects the leading edge of the next Low Resolution signal pulse (voltage transitions to high). The PCM monitors the number of High Resolution counts to verify proper CKP sensor operation. The scan tool parameter that displays the results of this calculation is CKP:Lo Resolution Angle. The value displayed is the number of degrees that the camshaft deviates [either advanced (+) or retarded (-)] from its normal alignment with the crankshaft. During normal operation, on a vehicle with little or no timing chain wear, the value displayed would be near 0°Dev.

### Conditions for Setting the DTC

• | Engine Speed between 500 and 4000 RPM (LT1), 675 and 4000 RPM (LT4)

• | Ignition Voltage between 9 and 17 volts

• | CKP:Lo Resolution Angle goes outside of the range from -21°Dev to +51°Dev No signal from the CKP sensor will also cause this condition.

### Action Taken When the DTC Sets

• | The PCM will illuminate the Malfunction Indicator Lamp (MIL) on the second consecutive drive trip that the diagnostic runs and fails.

• | The PCM will record operating conditions at the time the diagnostic fails. The first time the diagnostic fails, this information will be stored in Failure Records. If the diagnostic reports a failure on the second consecutive drive trip, the operating conditions at the time of failure will be written to Freeze Frame and the Failure record will be updated.

### Conditions for Clearing the MIL/DTC

• | The PCM will turn the MIL OFF after three consecutive drive trips that the diagnostic runs and does not fail.

• | A last test failed (Current DTC) will clear when the diagnostic runs and does not fail.

• | A History DTC will clear after forty consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | PCM battery voltage is interrupted.

• | Using a Scan tool.

### Diagnostic Aids

The following mechanical problems may cause this DTC to set:

• | Poor connections/terminal tension at the sensor.

• | Excessive timing chain/gear wear.

• | Excessive distributor drive backlash or other mechanical distributor problem.

• | Crankshaft reluctor wheel damage or improper installation.

• | Engine front cover assembly damage.

• | The sensor coming in contact with the reluctor wheel.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If the DTC cannot be duplicated, the information included in the Freeze Frame and/or Failure Records data can be useful in determining how many miles since the DTC set. The Fail Counter and Pass Counter can also be used to determine how many ignition cycles the diagnostic reported a pass and/or a fail. Operate vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that were noted. This will isolate when the DTC failed.

For intermittents, refer to Symptoms .

### Test Description

Number(s) below refer to step numbers on the diagnostic table.

1. Crankshaft RPM should be similar to Engine Speed within approximately ± 75 RPM.

Important: During hard acceleration these two parameters can differ widely from each other due to time variances in the PCMs internal calculating processes. This difference could show up in a snapshot. If other parameters indicate a hard acceleration condition, the difference in the two values should be disregarded.

1. If there is excessive timing chain/gear wear, the camshaft has a tendency to retard on acceleration and to advance on deceleration. This parameter will indicate a positive value as the crankshaft accelerates, then flip to a negative value as the crankshaft decelerates. This may be more apparent while driving the vehicle than it is under a no-load situation.

2. If the reluctor wheel keyway moves off of the key in the crankshaft before the damper hub is completely installed, it is possible to pinch the reluctor wheel in an incorrect position. This will cause the CKP: Lo Res Angle parameter to be skewed. If the distributor drive pin is not properly indexed into the distributor and then the distributor is drawn into place with the mounting bolts, the CKP: Lo Res Angle parameter will be skewed. Check the condition of the distributor shaft for evidence of this condition.

3. The parameter Cyl Mode Misfire Index is the difference in crankshaft deceleration from one reference period to the next (in counts). On a perfect engine this value would equal zero, however, due to normal variations in engine operation, a value less than 1000 is acceptable. In this diagnostic table, Cyl Mode Misfire Index is being used to detect erratic signals from the CKP sensor. The following conditions should be met before using this parameter:

• | Engine idling at normal operating temperature.

• | All accessories OFF.

• | No apparent engine misfire. DTC P0300 may or may not be set since that diagnostic relies on data from this sensor. If the engine is misfiring, this needs to be corrected before proceeding. Refer to Symptoms .

4. With the signal generator set to 54 mph, the Crankshaft RPM should indicate approximately 900 RPM.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Is DTC P1371 or P1373 also set? | -- | Go to that DTC Table first | Go to Step 3
3 |

1. Start the engine.
2. Using the scan tool, monitor Crankshaft RPM.

Is RPM indicated?

--

Go to Step 4

Go to Step 9

4 | Using the scan tool, monitor CKP: Lo Res Angle. The actual value may fluctuate, but should remain within the range shown. Is the value within the range specified? | -10° Dev to +7° Dev | Go to Step 7 | Go to Step 5
5 | While observing CKP: Lo Res Angle, Quickly rev the engine once and allow it to return to idle. Does the CKP: Lo Res Angle change from a positive value on acceleration to a negative value on deceleration? | -- | Go to Step 15 | Go to Step 6
6 | Does the CKP: Lo Res Angle appear to be fixed at or near a value outside the specified range? | - 10° Dev to +7° Dev | Go to Step 16 | Go to Step 7
7 | Important: Review the information in the Test Description before proceeding. Using the scan tool, monitor Cyl Mode Misfire Index (in the Misfire data list) with the engine idling. Typically this value should remain below 1000. Is the value below the specified value? | 1000 | Go to Step 8 | Go to Step 12
8 |

1. Turn the ignition ON, engine OFF, review Freeze Frame and/or Failure Records data for this DTC and note parameters.
2. Ignition OFF for 15 seconds.
3. Start the engine and operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in Freeze Frame/Failure Records as possible. Special operating conditions that need to be met before the PCM will run this diagnostic, where applicable, are listed in Conditions for Setting the DTC.
4. Using the scan tool, select DTC, Specific, then enter the DTC number which was set.

Does the scan tool indicate that this diagnostic failed this ignition?

--

Go to Step 9

Go to Diagnostic Aids

9 |

1. Turn the ignition ON, engine OFF.
2. Disconnect the Crankshaft Position Sensor harness connector.
3. Connect a test light (J 34142-B) from the ignition feed circuit in the Crankshaft Position Sensor harness connector to battery ground.

Is the test light ON?

--

Go to Step 10

Go to Step 17

10 | Connect a test light (J 34142-B) between terminal A and terminal B in the Crankshaft Position Sensor harness connector. Is the test light ON? | -- | Go to Step 11 | Go to Step 19
11 |

1. Install the Signal Generator Tester (J 33431-B) to the signal circuit in the Crankshaft Position Sensor harness connector (one terminal connected to the signal circuit and the other to ground).
2. Turn the ignition ON, Tester ON and set to generate a 54 mph signal.
3. Using the scan tool, monitor Crankshaft RPM.

Does the scan tool indicate Crankshaft RPM?

--

Go to Step 17

Go to Step 13

12 | Visually inspect the Crankshaft Position Sensor for the following conditions:

• | Physical damage.

• | Loose or improper installation.

• | Wiring routed too closely to secondary ignition components.

• | Poor connections/terminal tension at the sensor and/or the PCM.

Was a problem found and corrected?

--

Go to Step 23

Go to Step 21

13 |

1. Turn the ignition OFF.
2. Disconnect PCM connector C1.
3. Using DVM J 39200, check continuity of the signal circuit from the sensor harness connector to the PCM connector.

Does the DVM indicate continuity?

5 ohms

Go to Step 14

Go to Step 20

14 | Using the J 39200, measure the resistance between the signal circuit and ground. Does the DVM indicate infinite resistance? | -- | Go to Step 22 | Go to Step 20
15 | Check for excessive timing chain/gear wear. Refer to Engine Unit Repair, Section 6A. Is the action complete? | -- | Go to Step 23 | --
16 | Check for poor connections/terminal tension at the sensor. If the connections are OK, Check for proper reluctor wheel installation. Refer to Engine Unit Repair, Section 6A. Is the action complete? | -- | Go to Step 23 | --
17 | Check for poor connections/terminal tension at the sensor. Was a problem found and corrected? | -- | Go to Step 23 | Go to Step 21
18 | Repair the ignition feed circuit. Is the action complete? | -- | Go to Step 23 | --
19 | Repair the ground circuit. Is the action complete? | -- | Go to Step 23 | --
20 | Repair the signal circuit. Is the action complete? | -- | Go to Step 23 | --
21 | Replace the Crankshaft Position Sensor. Refer to Crankshaft Position Sensor Replacement . Is the action complete? | -- | Go to Step 23 | --
22 | Important:: Replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | Go to Step 23 | --
23 |

1. Using the scan tool, select DTC, Clear Info.
2. Start the engine and idle at normal operating temperature.
3. Select DTC, Specific, then enter the DTC number which was set.
4. Operate vehicle within the conditions for setting this DTC as specified in the supporting text, if applicable.

Does the scan tool indicate that this test ran and passed?

--

Go to Step 24

Go to Step 2

24 | Using the scan tool, select Capture Info, Review Info. Are any DTCs displayed that have not been diagnosed? | Go to the applicable DTC table | System OK