C0268 ABS Code

[A468bu]

This is a 2002 3500 4wd Silverado ABS code C0268 I cleared it and came right back up within 2 miles of driving. Any of you experience this yet? Its a code for the ABS pump, are these known to go bad?

 

Thanks

[GM-Tech]

The pumps don't go bad very often, but the module that controls it (EBCM) do and this can set that code.

[A468bu]

The pumps don't go bad very often, but the module that controls it (EBCM) do and this can set that code.

 

<{POST_SNAPBACK}>

 

 

 

 

Any way to diagnose this?

[GM-Tech]

Any way to diagnose this?

 

<{POST_SNAPBACK}>

 

 

 

sure, but pasting the diagostic chart into the forum is a mess. I'd say it's almost unreadable and impossible to follow. But here ya go. Good luck.

 

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DTC C0267 or C0268 and C067 or C068

Circuit Description

The EBCM applies the ground needed for pump motor activation. The low side of the pump motor has a feedback circuit to the EBCM. When the pump motor is commanded OFF and at rest, feedback voltage is high. When the pump motor is winding down after being commanded ON and then OFF, feedback voltage is low. The EBCM monitors this feedback voltage in order to determine if the motor is functioning properly.

 

Conditions for Running the DTC

The ignition is ON.

The vehicle speed is greater than 6 km/h (4 mph).

Conditions for Setting the DTC

The EBCM detects any of the following conditions:

 

An open or shorted pump motor

An open or shorted pump motor driver circuit

A seized pump motor

Action Taken When the DTC Sets

The EBCM disables the ABS.

The ABS indicator turns ON.

Conditions for Clearing the DTC

The conditions for setting the DTC are no longer present and you use the scan tool Clear DTCs function.

 

Diagnostic Aids

Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to the following:

 

• Testing for Electrical Intermittents

 

• Testing for Intermittent Conditions and Poor Connections

 

• Wiring Repairs

 

• Connector Repairs

 

Test Description

The numbers below refer to the step numbers on the diagnostic table.

 

It is imperative that the vehicle be driven to attempt to reset the DTC. Using the scan tool to perform a function test may not produce the same result, and therefore may cause misdiagnosis of the vehicle.

 

This step tests if the EBCM is capable of activating the ABS pump motor.

 

A shorted ABS pump motor may damage the EBCM. It is imperative that the steps in the table be followed in order to prevent damage to a replacement EBCM.

 

Step

Action

Values

Yes

No

 

Schematic Reference: ABS Schematics

 

Connector End View Reference: ABS Connector End Views

 

1

Did you perform the ABS Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - ABS

 

2

Use a scan tool in order to clear the DTCs.

Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does DTC C0267 set?

--

Go to Step 6

Go to Step 3

 

3

Does DTC C0268 set?

--

Go to Step 4

Go to Diagnostic Aids

 

4

Turn OFF the ignition.

Disconnect from the EBCM, the 2-way harness connector which contains the battery positive voltage circuit and the ground circuit.

Caution: Before servicing any electrical component, the ignition and start switch must be in the OFF or LOCK position and all electrical loads must be OFF, unless instructed otherwise in these procedures. If a tool or equipment could easily come in contact with a live exposed electrical terminal, also disconnect the negative battery cable. Failure to follow these precautions may cause personal injury and/or damage to the vehicle or its components.

 

Disconnect the negative battery cable.

Disconnect the positive battery cable.

Place one lead of a DMM on the positive battery cable where the cable normally connects to the battery.

Place the other lead on the battery positive voltage circuit terminal within the 2-way EBCM harness connector.

Measure the total resistance between the positive battery cable and the EBCM.

Does the resistance measure within the specified range?

0.0-0.2 ohms

Go to Step 5

Go to Step 10

 

5

Use a DMM to measure the resistance of the ground circuit.

 

Does the resistance measure within the specified range?

0.0-0.2 ohms

Go to Step 7

Go to Step 11

 

6

 

Important

On some applications, it may be necessary to separate the EBCM from the BPMV in order to perform this test. Also, DTC C0268 may set when this test is performed.

 

 

Turn OFF the ignition.

Disconnect from the EBCM, the ABS pump motor pigtail connector. For systems which have no pump motor pigtail, it is necessary to separate the EBCM from the BPMV in order to gain access to the pump motor connector of the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .

Use a connector adapter test kit in order to connect a test lamp between the ABS pump motor power and ground circuits at the pump motor connector of the EBCM.

Turn ON the ignition.

Use the scan tool in order to clear the DTCs.

Use the scan tool in order to perform an ABS Function Test.

Does DTC C0267 set?

--

Go to Step 12

Go to Step 9

 

7

 

Important

On some applications, it may be necessary to separate the EBCM from the BPMV in order to perform this test. Also, DTC C0268 may set when this test is performed.

 

 

Reconnect both battery cables.

Disconnect from the EBCM, the ABS pump motor pigtail connector. For systems which have no pump motor pigtail, it is necessary to separate the EBCM from the BPMV in order to gain access to the pump motor connector of the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .

Use a connector adapter test kit in order to connect a test lamp between the ABS pump motor power and ground circuits at the pump motor connector of the EBCM.

Turn ON the ignition.

Use the scan tool in order to clear the DTCs.

Use the scan tool in order to perform an ABS Function Test.

Does the test lamp illuminate and then turn OFF when the Function Test is performed?

--

Go to Step 13

Go to Step 8

 

8

Use a DMM in order to measure the resistance across the ABS pump motor.

 

Does the resistance measure within the specified range?

0.3-1.0 ohms

Go to Step 12

Go to Step 14

 

9

Inspect for poor connections at the pump motor pigtail connector. Refer to Testing for Intermittent and Poor Connections and to Connector Repairs in Wiring Systems.

 

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

 

10

Repair the high resistance in the underhood electrical center or the battery positive voltage circuit. Refer to Wiring Repairs in Wiring Systems.

 

Did you complete the repair?

--

Go to Step 15

--

 

11

Repair the high resistance in the ground circuit. Refer to Wiring Repairs in Wiring Systems.

 

Did you complete the repair?

--

Go to Step 15

--

 

12

 

Important

Following EBCM replacement, use the scan tool to perform the Tire Size Calibration procedure and the Trim Level Calibration procedure, if applicable.

 

 

Replace the EBCM. Refer to Electronic Brake Control Module (EBCM) Replacement .

 

Did you complete the replacement?

--

Go to Step 15

--

 

13

Replace the BPMV. Refer to Brake Pressure Modulator Valve (BPMV) Replacement .

 

Did you complete the replacement?

--

Go to Step 15

--

 

14

 

Important

Following EBCM replacement, use the scan tool perform the Tire Size Calibration procedure and the Trim Level Calibration procedure, if applicable.

 

 

Replace the EBCM and the BPMV. Refer to Electronic Brake Control Module (EBCM) Replacement and to Brake Pressure Modulator Valve (BPMV) Replacement .

 

Did you complete the replacements?

--

Go to Step 15

--

 

15

Use a scan tool in order to clear the DTCs.

Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC reset?

--

Go to Step 3

System OK

 

 

 

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