GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2002 🢒 DeVille 🢒 DTC 🢒 DTC P0336

Circuit Description

The powertrain control module (PCM) uses dual crankshaft position (CKP A and CKP B) sensors in order 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 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 in order to determine an initial crankshaft position, and to generate MEDRES (24X reference) and LORES (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 MEDRES signal to the camshaft position (CMP) sensor signal. If the PCM detects a valid CMP signal, and the MEDRES to CMP signal correlation is correct, the PCM determines that CKP sensor A is at fault. However, if the MEDRES to CMP correlation is incorrect, the PCM determines that CKP sensor B is at fault. If the PCM determines that CKP sensor B is at fault, DTC P0385 will set. The PCM will switch from angle based mode to Time Based mode A using CKP sensor A signal input. If, after switching to Time Base A mode, the PCM detects an intermittent loss of CKP sensor A signal, DTC P0336 will set.

Conditions for Running the DTC
    • The engine is cranking or running.
    • DTC P0385 has set.
    • Cam faults are not present.

Conditions for Setting the DTC

The PCM detects an intermittent loss of CKP Sensor A 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

If the condition is intermittent, refer to Intermittent Conditions in Symptoms.

Procedures for Selecting Crank Position Sensing Decode Mode

Diagnosing the crankshaft position sensors may require enabling 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 the ignition switch to the RUN/ON position.
    • 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.

  1. During normal operation, the PCM uses the angle mode in order 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 in order 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 B signal, DTC P0385 will set. DTC P0336 will only set if a problem with CKP sensor A occurs while in Time A mode. DTC P0385 must be diagnosed first.

    2.

  2. To properly verify any repair to CKP sensor A harness connectors, the system must be commanded to operate in Time A mode. This forces the PCM to use CKP sensor A in order to determine engine position. If the system is functioning normally, DTC P0336 should not reset.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: If DTC P0385 is set, diagnose DTC P0385 before continuing with this table.

  1. Install the scan tool.
  2. Turn the ignition switch to the RUN position, with the engine OFF.
  3. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  4. Disconnect CKP Sensor A connector.
  5. Test the 12-volt reference circuit of the CKP sensor A for the following conditions:
    6. • An intermittent open
    • An intermittent short to ground
    • Poor terminal contact at CKP sensor A
  6. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 3

3
  1. Test the low reference circuit of the CKP sensor A for the following conditions:
    2. • An intermittent open
    • Poor terminal contact at CKP sensor A
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring System.

Did you find and correct the condition?

Go to Step 6

Go to Step 4

4
  1. Test the signal 2 circuit of the CKP sensor A for the following conditions:
    2. • An intermittent open
    • An intermittent short to sensor 12-volt reference circuit or battery voltage
    • An intermittent short to ground or sensor low reference circuit
    • Poor terminal contact at CKP sensor A
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Step 5

5
  1. Test the following CKP sensor A circuits for poor terminal contact at the PCM:
    2. • Sensor 12-volt reference circuit
    • Sensor signal 2 circuit
    • Sensor low reference circuit
  2. If a condition is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

Go to Step 6

Go to Diagnostic Aids

6

  1. Lower the vehicle.
  2. Review and record the scan tool Failure Record Data.
  3. Clear the DTCs.
  4. Using the scan tool, command the system to operate in Time A mode. Refer to Procedures for Selecting Crank Position Sensing Decode Mode in Diagnostic Aids.
  5. Monitor the Specific DTC Information for DTC P0336.

Does the DTC run and pass?

Go to Step 7

Go to Step 2

7

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

Go to Diagnostic Trouble Code (DTC) List

System OK