GM Service Manual Online
For 1990-2009 cars only

Object Number: 439255  Size: MF
Engine Controls Components
Cell 22: CKP and Injection Timing Stepper Motor
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

The PCM provides a 5 volt supply for use in powering up the sensors. This test monitors the voltage present at terminals BRD13 (shared by boost and crankshaft position sensors) and BRD14 (the optical/fuel temperature sensor (Cam/HI. Res)).

Conditions for Setting the DTC

The ignition switch in the on position.

Conditions for Setting the DTC

The 5 volt reference is less than 1 volt.

Action Taken When the DTC Sets

    • The PCM will not illuminate the malfunction indicator lamp (MIL).
    • The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Records.

Conditions for Clearing the MIL/DTC

    • A History DTC will clear after forty consecutive engine warm up cycles, if this or any other emmision related diagnosic does not report any failures.
    • Use of a scan tool will clear the DTC codes.

Diagnostic Aids

During the time the failure is present, the setting of additional DTCs that share a 5 volt reference may also set.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

  1. Checks to confirm that a DTC is still present.

  2. Checks to determine if there is a 5 volt reference from the PCM.

  3. Checks to determine if there is a short-to-ground in the reference circuit or a short-to-ground in the PCM.

  4. This step determines if the short is being caused by one of the sensors on the engine or the short is in the wiring harness.

Step

Action

Value(s)

Yes

No

1

Important: Before clearing the DTCs, use the scan tool Capture Info to save Freeze Frame and Failure Records for reference. The control module's data is deleted once the Clear Info function is used.

Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?

--

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

2

  1. Install a scan tool.
  2. Crank the engine for 15 seconds or until start up.

Does the DTC reset?

--

Go to Step 3

Go to Step 5

3

  1. Turn the ignition ON leaving the engine OFF.
  2. Disconnect the boost sensor.
  3. With J 39200 DMM, probe the 5 volt reference circuit at the harness connector.

Is the voltage less than the specified value?

4.0 V

Go to Step 4

Go to Step 6

4

  1. Disconnect the PCM connector with the Boost sensor 5 volt reference circuit.
  2. With an J 35616-200 unpowered test lamp connected to B+, probe the 5 volt reference circuit at the PCM harness.

Is the test lamp ON?

--

Go to Step 7

Go to Step 8

5

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to those table(s).

Are any additional DTCs stored?

--

Go to the applicable DTC table

Go to Diagnostic Aids

6

Replace the Boost sensor. Refer to Boost Sensor Replacement .

Is the action complete?

--

Go to Step 11

--

7

With the J 35616-200 unpowered test lamp still probing the boost sensor 5 volt reference circuit at the PCM, disconnect each sensor, one at a time, that shares the 5 volt reference with the boost sensor.

Does the test lamp turn OFF when one of the sensors are disconnected?

--

Go to Step 9

Go to Step 10

8

  1. Disconnect the PCM connector with the fuel temperature sensor 5 volt reference circuit.
  2. With a J 35616-200 unpowered test lamp connected to B+, probe the fuel temperature 5 volt reference circuit at the PCM harness.

Is the test lamp ON?

--

Go to Step 10

Go to Step 11

9

Repair the short to ground in 5 volt reference circuit. Refer to Wiring Repairs.

Is the action complete?

--

Go to Step 11

--

10

Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Replace the PCM.

Is the action complete?

--

Go to Step 11

--

11

  1. Using the scan tool, clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number which was set.
  6. Operate the vehicle, with the Condition for Setting this DTC, until the scan tool indicates the diagnostic Ran.

Does the scan tool indicate the diagnostic Passed?

--

Go to Step 12

--

12

Does the scan tool display any additional undiagnosed DTCs?

--

Go to the applicable DTC table

System OK