GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2008 🢒 Vibe - FWD 🢒 Safety and Security 🢒 Supplemental Inflatable Restraints 🢒 DTC C1224

Circuit Description

The electronic brake control module (EBCM) monitors the engine RPM signals of the powertrain control module (PCM).

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC C1224 RPM Signal Circuit Malfunction

Conditions for Running the DTC
    • DTC C1224 can be set anytime the vehicle speed is above 30 km/h (19 mph).
        OR
    •  The traction control system is in operation.

Conditions for Setting the DTC

The EBCM detects an open, high resistance, or short in the engine RPM signal from the PCM.

Action Taken When the DTC Sets
    • The ABS is disabled.
    • The ABS warning indicator turns ON.
    • The traction control and vehicle stability control (VSC) is disabled.
    • The VSC warning indicator turns ON.

Conditions for Clearing the DTC

The condition responsible for setting the DTC no longer exists and the scan tool Clear DTCs function is used.

Diagnostic Aids

Thoroughly inspect the wiring and the connectors. An incomplete inspection of the wiring and the connectors may result in a misdiagnosis, causing a part replacement with the reappearance of the malfunction.

The following are possible causes of the malfunction:

    • An open, high resistance, or short in the engine RPM signal circuit
    • An internal PCM malfunction

If an intermittent malfunction exists, refer to Testing for Intermittent Conditions and Poor Connections.

Test Description

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

  1. Test the engine RPM signal circuits of the EBCM for a high resistance, an open, or a short.

Step

Action

Value(s)

Yes

No

Schematic Reference: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic System Check - Vehicle

2

Test the engine RPM signal circuit of the electronic brake control module (EBCM) for a high resistance, an open, or a short. Refer to Circuit Testing and Wiring Repairs.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 3

3
  1. Disconnect the EBCM connector.
  2. Turn ON the ignition, with the engine OFF.
  3. Measure the voltage of the engine RPM signal circuit of the EBCM to a good ground. Refer to Circuit Testing and Wiring Repairs.

Is the voltage as specified?

10-14 V or below 1 V

Go to Step 4

Go to Step 5

4
  1. Disconnect the EBCM connector.
  2. Turn ON the ignition, with the engine running.
  3. Measure the voltage of the engine RPM signal circuit of the EBCM to a good ground. Refer to Circuit Testing and Wiring Repairs.

Is the voltage as specified?

10-14 V and pulsing below 1 V

Go to Step 6

Go to Step 5

5

Replace the powertrain control module (PCM). Refer to Powertrain Control Module Replacement.

Did you complete the replacement?

--

Go to Step 7

--

6

Inspect for poor connections at the EBCM and PCM connectors. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs.

Did you find and correct the condition?

--

Go to Step 7

Go to Step 2

7
  1. Use the scan tool in order to clear the DTCs.
  2. Operate the vehicle within the Conditions for Running the DTC, as specified in the supporting text.

Does the DTC reset?

--

Go to Step 2

System OK