Circuit Description
The powertrain control module (PCM) uses dual crankshaft position (CKP) A and CKP B sensors to determine crankshaft position. The PCM supplies an ignition voltage and a ground for each sensor. During engine rotation, a slotted ring, machined into the crankshaft, causes the sensors to return a series of ON and OFF pulses to the PCM. The PCM uses these pulses to decode the position of the engine crankshaft.
The PCM uses 2 basic methods of decoding the engine position, Angle Based and Time Based, using either CKP A or CKP B sensor input. During normal operation, the PCM uses the angle based method. In order to operate in this mode, the PCM must receive signal pulses from both CKP sensors. The PCM uses the signal pulses to determine an initial crankshaft position, and to generate medium resolution (24X reference) and low resolution (4X reference) signals. Once the initial crank position is determined, the PCM continuously monitors both sensors for valid signal inputs. As long as both signal inputs remain, the PCM will continue to use the Angle Based mode.
When either CKP signal is lost, the PCM will compare the medium resolution signal to the camshaft position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the medium resolution to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the medium resolution to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault. If the PCM determines that CKP sensor A is at fault, DTC P0335 will set. The PCM will switch from Angle Based mode to Time Based Mode B using CKP sensor B signal input. If, after switching to Time Based Mode B, the PCM detects an intermittent loss of CKP sensor B signal, DTC P0386 will set.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P0386 Crankshaft Position (CKP) Sensor B Performance
Conditions for Running the DTC
DTC P0386 runs continuously once the above conditions are met.
Conditions for Setting the DTC
The PCM detects that 5 CKP resyncs occurred within 10 seconds.
Action Taken When the DTC Sets
| • | The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. |
| • | The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the 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
The following conditions may cause this DTC to set:
| • | The crankshaft reluctor wheel is damaged or improperly installed. |
| • | The sensor is coming in contact with the reluctor wheel. |
| • | If the crankshaft rotates backwards, this DTC sets. This condition is only with vehicles equipped with a manual transmission. This condition can occur when a vehicle is on an incline and the clutch is released and an engine stall occurs. |
Excess crankshaft end play will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in any of the following conditions:
| • | A no start |
| • | A start and stall |
| • | Erratic performance |
An improperly installed crankshaft could cause excess crankshaft end play.
If the condition is intermittent, refer to Intermittent Conditions .
Procedures for Selecting Crank Position Sensing Decode Mode
When diagnosing the CKP sensors, it may be necessary to enable a specific decode mode (Angle, Time A, or Time B). To enable a specific crank decode using the scan tool, perform the following steps:
- Turn ON the ignition, with the engine OFF.
- Select Engine Output Controls.
- Select Crank Position Sensing Decode Mode.
- Select the desired mode (Angle, Time A, or Time B) and press Select State.
- Command the decode mode by pressing Command State.
The commanded state remains valid for the current ignition cycle. A specific decode mode can not be commanded with the engine running, or after commanding a desired decode mode. To command a different decode mode, you must cycle the ignition OFF and ON.
Test Description
The numbers below refer to the step numbers on the diagnostic table.
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During normal operation, the PCM uses the Angle Mode to determine engine position. In order to operate in this mode, the PCM must receive valid input from both CKP sensors. If the PCM detects a loss of CKP sensor A signal, the PCM switches to a Time B Mode using CKP sensor B input to determine engine position. If the PCM detects a loss of CKP sensor B, the PCM switches to a Time A Mode using CKP sensor A input to determine engine position. If the PCM detects a loss of CKP sensor A signal, DTC P0335 will set. DTC P0386 will only set if a problem with CKP sensor B occurs while in Time B Mode. DTC P0335 must be diagnosed first.
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To properly verify any repair to CKP sensor A harnesses/connectors, the system must be commanded to operate in Time B mode. This forces the PCM to use CKP sensor B to determine engine position. If the system is functioning normally, DTC P0386 should not reset.
Step | Action | Yes | No | ||||||
|---|---|---|---|---|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | |||||||||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | ||||||
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Important: If DTC P0335 is set, diagnose DTC P0335 before continuing with this table.
Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 3 | |||||||
3 | Test the low reference circuit of the CKP sensor B for an intermittent open. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 4 | ||||||
4 | Test the CKP sensor B signal 1 circuit for the following conditions:
Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 5 | ||||||
5 | Test for an intermittent and for a poor connection at the CKP sensor A. Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Step 6 | ||||||
Test for an intermittent and for a poor connection at the powertrain control module (PCM). Refer to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 7 | Go to Diagnostic Aids | |||||||
7 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 8 | ||||||
8 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | ||||||
