For 1990-2009 cars
Engine Controls Components
Engine Speed Output, CKP and CMP Sensors
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice

### Circuit Description

The Crankshaft Position (CKP) sensor sends pulses to the PCM as the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses to synchronize the ignition and fuel injector operation, and to time the interval between each CKP pulse. The PCM determines when an excessive change in crankshaft speed occurs by comparing each new time interval with the previous interval. A misfire causes an unexpected change in the crankshaft speed. A certain amount of acceleration/deceleration is expected between each firing stroke, but if the crankshaft speed changes more than an expected amount, the PCM interprets this as a misfire. The interval between CKP sensor pulses is extremely small. At high engine speeds, slight variations in the following components make misfire detection difficult:

• | Crankshaft

• | Reluctor wheel

• | CKP sensor

The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when performing detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.

Perform the learning procedure after the following actions:

• | A PCM replacement

• | Any operation or repair involving the crankshaft, the CKP sensor, or the CKP sensor to reluctor wheel gap relationship.

• | An engine replacement.

• | The ignition switch is in the ON position until the battery is drained.

Important: A PCM power disconnect with the ignition ON may erase the stored pulse value and set the DTC P1336.

Disconnecting the PCM will not erase the learned Crankshaft Position System Variation as long as the ignition switch is in the OFF position.

Important: Reprogramming the PCM does not require running the Crankshaft Position System Variation Learn Procedure unless the PCM is new or from another vehicle.

A DTC P1336 sets if the Crankshaft Position System Variation is not within an acceptable range, or can not be learned.

### Conditions for Running the DTC

There are no crankshaft position (CKP) or camshaft position (CMP) sensor DTCs

### Conditions for Setting the DTC

The PCM has not learned the Crankshaft Position System Variation

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• | The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Freeze Frame and/or Failure Records.

### Conditions for Clearing the MIL/DTC

• | The PCM turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.

• | A last test failed, or current DTC, clears when the diagnostic runs and does not fail.

• | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.

• | Use a scan tool in order to clear the MIL and the DTC.

### Diagnostic Aids

If the Crankshaft Position System Variation Learn Procedure cannot be learned, inspect for the following conditions:

• | A chipped or damaged reluctor wheel

• | Incorrect alignment of the CKP sensor to the reluctor wheel

• | Excessive crankshaft run-out

• | Interference in the signal circuit to the CKP sensor

• | Incorrect ratio of crankshaft to camshaft pulses

| Important: If the PCM receives an incorrect crankshaft to camshaft ratio the PCM will not allow the scan tool to enable the learn procedure.

Engine diagnostic misfire is not operable when the engine is above 1000 RPM and DTC P1336 is set.

When the learn procedure is in progress and the engine speed is at 4000 RPM, a decrease in engine speed will occur. During the engine coast down, the PCM monitors the CKP sensor signal and stores the pattern. This pattern is used to determine if the crankshaft speed variations are due to misfire.

### Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

1. The PCM enables the learn process after 65°C (150°F) is reached. Engine deceleration occurs when the learn procedure is in progress. The PCM monitors and records the CKP sensor signal during engine coast-down conditions.

2. Test in Progress on the scan tool indicates the PCM is performing the learn procedure. If the PCM receives an incorrect crankshaft to camshaft pulse ratio, an incorrect transmission range signal input, corrupted communication, or no change in the brake switch input, the learn procedure will not be allowed.

3. If a repair is necessary due to a condition which prevented the learn procedure from enabling, the Crankshaft Position System Variation Learning Procedure must be performed.

4. The ignition must be in the OFF position for at least 10 seconds after the learn procedure is complete and the engine RPM has returned to idle. The PCM saves the signal data after these conditions are met.

Step | Action | Value(s) | Yes | No
--- | --- | --- | --- | ---
1 | Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | Go to Step 2 | Go to Powertrain On Board Diagnostic (OBD) System Check
2 | Perform the Crankshaft Position System Variation Learning Procedure as follows.

1. Install the scan tool.
2. Apply the vehicle's parking brake.
3. Block the drive wheels.
4. Close the hood.
5. Place the vehicle's transmission in Park (A/T) or Neutral (M/T).
6. Idle the engine until the specified engine coolant temperature value is reached.
7. Turn OFF all the accessories.
8. Apply the brakes for the duration of the procedure.

Important: While the learn procedure is in progress, release the throttle immediately when the engine starts to decelerate. The engine control is returned to the operator and the engine will respond to throttle position after the learn procedure is complete.

9. Enable the Crankshaft Position System Variation Learning Procedure with the scan tool.
10. Slowly raise the engine RPM to the specified value.
11. Immediately release the throttle when the engine speed decreases.

Does the scan tool indicate the Learn Status: Learned This Ignition?

65°C (150°F)

4000 RPM

Go to Step 5

Go to Step 3

3 | Attempt the Crankshaft Position System Variation Learn Procedure as many times as the specified value. Does the scan tool indicate the Learn Status: Learned This Ignition? | 3 | Go to Step 5 | Go to Step 4
4 | Inspect the Crankshaft Position (CKP) sensor and the crankshaft reluctor wheel for damage. Refer to Diagnostic Aids. Did you find a condition? | -- | Go to Step 6 | Go to Diagnostic Aids
5 | Turn OFF the ignition for 15 seconds. Is the action complete? | -- | Go to Step 7 | --
6 | Replace the Crankshaft Position (CKP) sensor and/or reluctor wheel. Refer to Crankshaft Position Sensor Replacement or Crankshaft and Bearings Removal in Engine Mechanical 5.7L. Is the action complete? | -- | Go to Step 7 | --
7 |

1. Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
2. Idle the engine at the normal operating temperature.
3. Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.

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

--

Go to Step 8

Go to Step 2

8 | Select the Capture Info option and the Review Info option using the scan tool. Does the scan tool display any DTCs that you have not diagnosed? | -- | Go to the applicable DTC table | System OK