Circuit Description
The powertrain control module (PCM) uses dual crankshaft position (CKP) A and CKP B sensors to determine crankshaft position. The PCM supplies a 12- volt reference and a low reference 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 two 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. The PCM will switch from angle based mode to Time Based Mode A using CKP sensor A signal input. If the PCM detects no CKP sensor B signal, DTC P0385 sets.
Conditions for Running the DTC
The engine is cranking or running.
Conditions for Setting the DTC
The PCM detects a loss of CKP sensor B signal.
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 .
Ignition system DTCs set with the ignition in the Start position if the starter relay or the starter is inoperative. When the PCM enables starter operation, the PCM also initiates the diagnostic test routines for DTCs P0335, P0340, and P0385. If a condition exists which prevents the engine from cranking, the PCM will not receive signal input from the CKP and CMP sensors, and the DTCs will set.
If DTC P0615 is set, diagnose DTC P0615 first. If DTC P0335, P0340, and/or P0385 are set and no condition is found, inspect for the following conditions:
| • | Is there a no-crank condition or an intermittent no-crank condition? |
| • | Was an attempt made to crank the engine with the shift lever not in Park or Neutral? |
Procedures for Selecting Crank Position Sensing Decode Mode
When diagnosing the crankshaft position 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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This step determines if the 12-volt reference circuit to the CKP A, CKP B, and the CMP is shorted to a ground. If all 3 DTCs are set, this indicates the circuit is shorted to a ground or a sensor is internally shorted. All 3 DTCs set because the 12-volt reference circuit are internally connected within the PCM. The engine will not start with this condition.
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DTC P0336 indicates an intermittent loss of CKP sensor A signal while in Time A mode. DTC P0336 only sets after the PCM detects a loss of CKP sensor B signal and has switched to Time A mode.
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.
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During engine operation, if moving the harnesses and connectors related to CKP sensor B results in a switch to Time A mode, an intermittent condition in the harnesses or connectors is present. This may cause an engine stall condition. If the harnesses and connectors are OK, CKP sensor B may be the cause of the intermittent condition.
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In order to test the CKP sensor B signal circuit, the PCM must be commanded to Time B mode using the scan tool. This allows the PCM to monitor input signals from CKP sensor B. Refer to Diagnostic Aids for the procedures to selecting the Crank Decode Mode.
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-Engine Controls? | Go to Step 2 | |||||||||
Are all three DTCs P0335, P0340, and P0385 set? | Go to Step 11 | Go to Step 3 | |||||||||
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Important: If DTC P0336 is also set, continue with the diagnostic table for DTC P0385 before diagnosing DTC P0336.
Does the scan tool indicate the CKP sensor status as ANGLE? | Go to Step 4 | Go to Step 5 | |||||||||
Did you find and correct the condition? | Go to Step 18 | Go to Diagnostic Aids | |||||||||
5 |
Does the test lamp illuminate? | Go to Step 6 | Go to Step 8 | ||||||||
6 | Connect the test lamp between the 12-volt reference circuit of the CKP sensor B and the low reference circuit of the CKP sensor B. Does the test lamp illuminate? | Go to Step 7 | Go to Step 9 | ||||||||
Does the scan tool indicate an RPM while touching the test lamp to the signal circuit? | Go to Step 12 | Go to Step 10 | |||||||||
8 | Test the 12-volt reference circuit of the CKP sensor B for an open. Refer to Testing for Continuity and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 | ||||||||
9 | Test the low reference circuit of the CKP sensor B for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 | ||||||||
10 | Test the CKP sensor B signal 1 circuit for the following conditions:
Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 13 | ||||||||
11 | Test the 12-volt reference circuit of the CKP sensor A, the CKP sensor B, and the CMP sensor for a grounded circuit. Refer to Testing for Short to Ground and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 17 | ||||||||
12 | Test for an intermittent and for a poor connection at the CKP sensor B. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 14 | ||||||||
13 | Test for an intermittent and for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 18 | Go to Step 17 | ||||||||
14 | Remove the CKP sensor B. Refer to Crankshaft Position Sensor Replacement . Did you find and correct the condition? | Go to Step 18 | -- | ||||||||
15 | Visually inspect the CKP sensor reluctor wheel for damage or looseness. Refer to Crankshaft and Bearing Cleaning and Inspection in Engine Mechanical. Did you find and correct the condition? | Go to Step 18 | Go to Step 16 | ||||||||
16 | Replace the affected CKP sensor. Refer to Crankshaft Position Sensor Replacement . Did you complete the replacement? | Go to Step 18 | -- | ||||||||
17 | Replace the PCM. Refer to Powertrain Control Module Replacement . Did you complete the replacement? | Go to Step 18 | -- | ||||||||
18 |
Did the DTC fail this ignition? | Go to Step 2 | Go to Step 19 | ||||||||
19 | Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | System OK | |||||||||
