GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The crankshaft position (CKP) sensor used on this engine is actually 2 sensors within a single housing. There are separate power, ground (reference low) and signal circuits connecting both sensors to the powertrain control module (PCM). The PCM supplies 12 volts to the CKP sensors.

The PCM can use three different modes of decoding crankshaft position. During normal operation, the PCM performs an Angle Based calculation using both signals to determine crankshaft position. The dual sensor allows the engine to run even if one signal is lost. If either signal is lost, the PCM switches to a Time Based method of calculating crankshaft position. If the system is operating in Time A mode, the PCM is using only the signal from sensor A. Time B indicates that the sensor B signal is being used. If the lost signal is restored, the PCM will continue to operate in Time A or B mode for the remainder of the current key cycle. The PCM will automatically revert back to the Angle mode on the next start up if the fault is not present. The scan tool can display the Crank Position Sensing Decode Mode.

Conditions for Running the DTC

The engine is cranking or running.

Conditions for Setting the DTC

The PCM detects a problem with the 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

Notice: Use the connector test adapter kit J 35616-A for any test that requires probing the following items:

   • The PCM harness connectors
   • The electrical center fuse/relay cavities
   • The component terminals
   • The component harness connector
Using this kit will prevent damage caused by the improper probing of connector terminals.

If the problem is intermittent, refer to Intermittent Conditions .

CKP/CMP sensor DTCs may set if the key is turned to Start and the starter is inoperative. If P0335, P0340, and P0385 are set and no trouble is found, check for the following:

    • 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 P/N?

Test Description

The number below refers to the step number on the diagnostic table.

  1. During normal operation the CKP Sensor Status parameter should always indicate Angle. If Time  A or Time B is displayed, a problem has been detected. For example, if the scan tool indicates Time A, the system is using the signal from CKP sensor A. CKP sensor B and the related circuits should be diagnosed.

Step

Action

Values

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

Does the engine start and run?

--

Go to Step 3

Go to Step 5

3

  1. Start the engine.
  2. Select CKP Sensor Status on the scan tool.

Does the scan tool indicate CKP Sensor Status Angle?

--

Go to Step 4

Go to Step 5

4

Move the related harnesses and the connectors, by hand only, while monitoring the scan tool display.

Does CKP Sensor Status change to Time A or to Time B, or does an engine stall occur?

--

Go to Step 12

Go to Intermittent Conditions

5

The following steps apply to the sensor and to the related circuitry that is malfunctioning. For example, if the scan tool indicates Time A, the system is using the signal from CKP sensor A. CKP sensor B and the related circuits should be diagnosed.

  1. Turn the key to OFF.
  2. Disconnect the CKP sensor.
  3. Turn the key to ON.
  4. Using the DMM connected to ground, measure the voltage on the 12-volt reference circuit at the CKP sensor harness connector.

Does the DMM indicate the specified voltage?

B+

Go to Step 6

Go to Step 13

6

Connect the DMM between the 12-volt reference circuit and the low reference circuit in the CKP sensor harness connector.

Does the DMM indicate the specified voltage?

B+

Go to Step 7

Go to Step 14

7

For the following test, the PCM must be commanded to look at the sensor being tested. Set the Crank Position Sensing Decode Mode to Time A when testing sensor A, and to Time B when testing sensor B.

  1. Turn the key to OFF and wait 15 seconds.
  2. Turn the key to ON.
  3. Clear the DTCs.
  4. Using the scan tool, command the system to operate in the appropriate Time mode for the sensor being tested, as explained above.
  5. Monitor the 24X Crank Sensor Data on the scan tool.
  6. Using a test lamp connected to B+, momentarily touch the signal circuit several times.

Does the scan tool indicate RPM?

--

Go to Step 19

Go to Step 8

8

  1. Turn the key to OFF.
  2. Disconnect the PCM connector.
  3. Turn the key to ON.
  4. Using the DMM, check for the presence of voltage on the signal circuit.

Does the scan tool indicate voltage?

--

Go to Step 17

Go to Step 9

9

Using the DMM, check the signal circuit for continuity between the CKP sensor harness connector and the PCM harness connector.

Does the DMM display the value shown or lower?

5 ohms

Go to Step 10

Go to Step 15

10

Using the DMM, check for continuity between the signal circuit and ground.

The DMM should display infinite resistance.

Does the DMM display infinite resistance?

--

Go to Step 11

Go to Step 16

11

Using the DMM, check for continuity between the CKP sensor A and the CKP sensor B signal circuits.

The DMM should display infinite resistance.

Does the DMM display infinite resistance?

--

Go to Step 21

Go to Step 18

12

Repair the harness and connections as necessary. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

13

Repair the sensor 12-volt reference circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

Go to Step 21

14

Repair the open or the high resistance in the low reference sensor circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

Go to Step 21

15

Repair the open or the high resistance in the sensor signal in the circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

Go to Step 21

16

Repair the sensor signal circuit that is shorted to ground. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

17

Repair the sensor signal circuit that is shorted to power. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

18

Repair the signal circuits that are shorted together. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 23

--

19

Check for poor connections and for poor terminal tension at the CKP sensor. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 20

20

  1. Replace the CKP sensor. Refer to Crankshaft Position Sensor Replacement .
  2. Perform the Crankshaft Position System Variation Learn after replacing the sensor.

Did you complete the replacement?

--

Go to Step 23

--

21

Check for poor connections and for poor terminal tension at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 23

Go to Step 22

22

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

--

Go to Step 23

--

23

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the engine for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 24

Go to Step 2

24

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