GM Service Manual Online
For 1990-2009 cars only

Object Number: 221438  Size: SF
ABS Components
Antilock Brake System Schematics

System Description

This DTC detects an internal malfunction of the Electronic Brake Control Module (EBCM).

Conditions for Setting the DTC

DTC C0550 is set if the EBCM has an internal malfunction.

Action Taken When the DTC Sets

    • A malfunction DTC stores.
    • The ABS disables.
    • The ABS 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

Use the enhanced diagnostic function of the Scan Tool in order to measure the frequency of the malfunction.

Clear the DTCs after completing the diagnosis. Test drive the vehicle for 3 drive cycles in order to verify that the DTC does not reset. Use the following procedure in order to complete one drive cycle:

  1. Start the vehicle.
  2. Drive the vehicle over 16 km/h (10 mph).
  3. Stop the vehicle.
  4. Turn the ignition to the OFF position.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. The Diagnostic System Check must be the starting point for any ABS related diagnosis.

  2. Determines if the condition that caused the DTC to set is currently present.

  3. Determines if the condition that set this DTC is intermittent.

  4. Determines if the condition that set this DTC is present during an ABS stop.

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Connect a scan tool to the Data Link Connector (DLC).
  2. Turn the ignition switch to the ON position.
  3. Select Diagnostic Trouble Codes (DTCs) under Application Menu on the scan tool.
  4. Select DTC Information on the scan tool.
  5. Select Current DTC on the scan tool.

Is DTC C0550 set as a Current DTC?

--

Go to Step 5

Go to Step 3

3

  1. Select Diagnostic Trouble Codes (DTC) on the scan tool.
  2. Select Clear DTC Information on the scan tool.
  3. Turn the ignition switch to the LOCK position.
  4. Wait 10 seconds then turn the ignition switch to the ON position.
  5. Select Diagnostic Trouble Codes (DTC) on the scan tool.
  6. Select Current DTC on the scan tool.

Is DTC C0550 set as a Current DTC?

--

Go to Step 5

Go to Step 4

4

  1. Test drive the vehicle at 24 km/h (15 mph) for 30 seconds.
  2. When driving conditions permit, perform an ABS stop bringing the vehicle to a complete stop.
  3. Park the vehicle and engage the parking brake.
  4. Select Diagnostic Trouble Codes (DTC) on the scan tool.
  5. Select DTC Information on the scan tool.
  6. Select Current DTC on the scan tool.

Is DTC C0550 set as a Current DTC?

--

Go to Step 5

Go to Step 6

5

Replace the brake pressure modulator valve assembly. Refer to Brake Pressure Modulator Valve Assembly Replacement .

Is the repair complete?

--

Go to Diagnostic System Check

--

6

A malfunction is not present at this time. Refer to Diagnostic Aids for additional information regarding this DTC.

Is the action complete?

--

Go to Diagnostic System Check

--