Circuit Description
The Crankshaft Position (CKP) sensor sends pulses to the PCM when the reluctor wheel teeth rotate past the CKP sensor. The PCM uses the CKP pulses in order to synchronize the ignition and the fuel injector operation, and in order to time the interval between each CKP pulse. The PCM determines when an excessive change in the 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 or 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:
| • | The crankshaft |
| • | The reluctor wheel |
| • | The CKP sensor |
The PCM learns variations during the Crankshaft Position System Variation Learning Procedure. The PCM compensates for these variations when it performs detect misfire calculations. Only a scan tool can command the PCM to perform the Crankshaft Position System Variation Learning Procedure again.
After the following actions, perform the learning procedure:
| • | 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 is from another vehicle.
A DTC P1336 sets if the Crankshaft Position System Variation is not within an acceptable range, or cannot be learned.
Conditions for Running the DTC
DTCs P0335, P0336, P0341, P0342, and P0343 are not set.
Conditions for Setting the DTC
The PCM has not learned the Crankshaft Position System Variation.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records. |
Conditions for Clearing the MIL/DTC
| • | The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail. |
| • | A current DTC, Last Test Failed, clears when the diagnostic runs and passes. |
| • | A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic. |
| • | Clear the MIL and the DTC with a scan tool. |
Diagnostic Aids
Important:
• Before you service the PCM, remove any debris from the PCM connector
surfaces. Inspect the PCM connector gaskets when you diagnose or replace
the PCM. Ensure that the gaskets are installed correctly. The
gaskets prevent contaminate intrusion into the PCM. • For any test that requires probing the PCM or probing
a component harness connector, use the J 35616
connector test adapter kit. Using this kit prevents damage
to the harness and component terminals. Refer to
Using Connector Test Adapters
in Wiring Systems. If the PCM receives an incorrect crankshaft-to-camshaft ratio, the PCM
will not allow the scan tool to enable the learn procedure.
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 |
The 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 the engine speed will occur. During the engine coastdown, 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.
For an intermittent condition, refer to Intermittent Conditions .
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
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.
-
Test in Progress status on the scan tool indicates the PCM is performing the learn procedure. If the PCM receives any of the signals listed below, the learn procedure will not be allowed.
-
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.
-
The ignition must be in the OFF position for at least 10 seconds after the learn procedure is complete, and after the engine RPM has returned to idle. The PCM saves the signal data after these conditions are met.
| • | An incorrect crankshaft-to-camshaft pulse ratio |
| • | An incorrect transmission range signal input |
| • | Corrupted communication |
| • | No change in the brake switch input |
Step | Action | Values | Yes | No |
|---|---|---|---|---|
1 | Did you perform the Diagnostic System Check-Engine Controls? | -- | Go to Step 2 | |
Perform the Crankshaft Position System Variation Learning Procedure as follows:
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. Does the scan tool indicate Learn Status: Learned This Ignition? | 65°C (150°F) 4000 RPM | Go to Step 5 | Go to Step 3 | |
Attempt the Crankshaft Position System Variation Learn Procedure as many times as the specified value. Refer to Crankshaft Position System Variation Learn . Does the scan tool indicate Learn Status: Learned This Ignition? | 3 | Go to Step 5 | Go to Step 4 | |
Inspect the Crankshaft Position (CKP) sensor and the crankshaft reluctor wheel for damage. Refer to Diagnostic Aids. Did you find any damage? | -- | Go to Step 6 | Go to Diagnostic Aids | |
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 . Did you complete the replacement? | -- | Go to Step 7 | -- |
7 |
Does the DTC run and pass? | -- | Go to Step 8 | Go to Step 2 |
8 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | -- | System OK |
