GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The engine control module (ECM) replicates the signal received from the crankshaft position (CKP) sensor. This signal is sent to the fuel injection control module (FICM) through the engine speed signal circuit. The FICM uses this replicated signal to generate injection current and control the recharge of the fuel injection high voltage circuits. When cranking, the FICM has full control of the fuel injectors. The only input the FICM uses at this time is the engine speed signal from the ECM. The FICM monitors the signal along with the injection request signals from the ECM after the engine is running. If there is a problem with this signal, a DTC could set.

Conditions for Running the DTC

The engine is cranking or running.

Conditions for Setting the DTC

The FICM does not receive a crank signal, but does receive injection requests from the ECM.

OR

The FICM receives an invalid crank signal from the ECM.

Action Taken When the DTC Sets

    • The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/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

A missing high resolution signal will cause a no-start condition.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

Connector End View Reference: Engine Control Module Connector End Views or Engine Controls Connector End Views

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Crank the engine.
  2. Use the scan tool to observe the Specific DTC information for the DTC that was set.

Does the scan tool display Last Test Failed?

--

Go to Step 3

Go to Intermittent Conditions

3

Important: Use the proper terminal from J 35616 Connector Test Adapter Kit.

  1. Turn OFF the ignition.
  2. Disconnect the fuel injection control module (FICM) harness connector containing the engine speed signal circuit.
  3. Measure the voltage from the engine speed signal circuit at the FICM harness connector to a good ground using an adapter terminal and a DMM. Refer to Troubleshooting with a Digital Multimeter in Wiring Systems.
  4. Crank the engine

Does the voltage measure within the specified range?

4-5 V

Go to Step 4

Go to Step 5

4

With the DMM still connected, measure the current from the engine speed signal circuit to a good ground.

Does the current measure less than the specified value?

10 mA

Go to Step 9

Go to Step 6

5

Does the voltage measure above the specified range?

4-5 V

Go to Step 7

Go to Step 8

6

Repair the short to reference voltage on the engine speed signal circuit. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 13

--

7

  1. Test for a short to battery voltage, ignition voltage, or either 5-volt reference on the engine speed signal circuit.
  2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

8

  1. Test the engine speed signal circuit for an open or a short to ground.
  2. Repair as necessary. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 11

9

  1. Inspect for poor connections at the FICM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 10

10

Replace the fuel injection control module. Refer to Fuel Injector Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

11

  1. Inspect for poor connections at the ECM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
  2. Repair as necessary. Refer to Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 13

Go to Step 12

12

Replace the ECM. Refer to Engine Control Module Replacement .

Did you complete the replacement?

--

Go to Step 13

--

13

  1. Use the scan tool in order to clear the DTCs.
  2. Turn OFF the ignition 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 14

Go to Step 2

14

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