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Discussion Starter · #1 ·
Hey guys, I posted earlier about my ABS and Brake light coming on. When it comes on this is the code CO265 Can someone tell me about this and what I can or can't do to fix it myself. Thanks in advance!!! The vehicle is an 01 Yukon XL.
 

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ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Module (Reground EBCM Ground) #04-05-25-002C - (Nov 23, 2005)
ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Module (Reground EBCM Ground)
2004-2005 Buick Rainier

2002-2006 Cadillac Escalade, Escalade EXT

2003-2006 Cadillac Escalade ESV

1999-2006 Chevrolet Silverado

2000-2006 Chevrolet Suburban, Tahoe

2002-2006 Chevrolet Avalanche

2002-2005 Chevrolet TrailBlazer, TrailBlazer EXT

2003-2005 Chevolet SSR

1999-2006 GMC Sierra

2000-2006 GMC Yukon, Yukon Denali, Yukon XL

2002-2005 GMC Envoy, Envoy XL

2002-2006 GMC Sierra Denali

2004-2005 GMC Envoy XUV

2002-2004 Oldsmobile Bravada

This bulletin is being revised to provide further diagnostic information and add 2006 model year full-size vehicles. Please discard Corporate Bulletin Number 04-05-25-002B (Section 05 -- Brakes).

Condition
Some customers may comment that the ABS light is on. Upon further inspection, DTCs C0265 and C0201 may be set in the brake module. It is also possible for DTC U1041 to set in other modules. There may also be a loss of communication with the brake module.

Cause
A poor connection at the EBCM ground is causing unnecessary replacements of brake modules.

Important: The EBCM Ground is different for each application. Refer to the list below for the proper ground reference:


• Midsize Utilities = Ground 304

• SSR = Ground 400

• Fullsize Trucks and Utilities = Ground 110


Correction
DO NOT REPLACE THE BRAKE MODULE.

Perform the following steps to improve the connection of the EBCM Ground:

Remove the EBCM Ground. The EBCM Ground is located on the frame beneath the driver's side door. If multiple grounds are found in this location, the EBCM ground can be identified as the heavy (12-gauge) wire.
Clean the area, front and back, using a Whiz Wheel®.
Install the ground, then the washer and then the bolt to the frame.
Important: It is important to use the bolts, washers and nuts specified in this bulletin. These parts have been identified due to their conductive finish.


Install a washer and nut to the back side of the frame.

Tighten
Tighten the nut to 9 N·m (79 lb in).

Cover the front and back side of the repair area using Rubberized Undercoating.
An additional check can be made to ensure a good connection for the Battery Cable to Frame ground. It is possible for this ground to cause similar symptoms with the ABS as described above.
 

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The ground is at the left body mount pocket that is part of the frame, and would be located beneath the drivers left foot. It is attached to the backside of that mount with a 13mm self threading bolt. Replace the bolt with a regular bolt and nut, and use star washers between the ground eyelet and frame for a good contact.
 

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Discussion Starter · #4 ·
Max, Thanks again, you are awsome as always. If I ever get to Southern Oregon, Im gonna buy you a case of ______________ (Your Choice!!!)
 

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Discussion Starter · #5 ·
OK, I replaced the bolt and used star washers. Still getting the pesky lights. Cant tell that there is any problem in the braking. Any other ideas??

Thanks once again!!!
 

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Discussion Starter · #6 ·
ttt, any ideas??
 

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From above "An additional check can be made to ensure a good connection for the Battery Cable to Frame ground. It is possible for this ground to cause similar symptoms with the ABS as described above. "

Did you check this as well?
 

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DTC C0265 or C0266
Circuit Description
The ABS relay supplies battery voltage to 6 valve solenoids. The electronic brake control module (EBCM) microprocessor applies the grounds needed to activate each solenoid. The low side of each solenoid coil has a feedback circuit to the EBCM microprocessor. When a solenoid is commanded OFF, the feedback voltage is high. When a solenoid is commanded ON, the feedback voltage is low.

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 an internal malfunction.

Action Taken When the DTC Sets
C0265
If equipped, the following actions occur:

The EBCM disables the DRP/ABS.
The ABS indicator turns ON.
The brake warning indicator turns ON.
C0266
If equipped, the following actions occur:

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

Important
Whenever the EBCM is replaced for DTC C0265 or C0266, the ABS pump motor and motor circuitry must be tested for the proper resistance. Refer to steps 7 and 8 in the diagnostic table below for testing procedures and resistance values.


C0265
Thoroughly inspect connections and circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent and Poor Connections , Testing for Electrical Intermittents , Connector Repairs and to Wiring Repairs in Wiring Systems.

C0266
Replace the EBCM if DTC C0266 continues to set intermittently.

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

This step tests if the battery positive voltage circuit can supply adequate power to the system relay.

A shorted ABS pump motor or shorted motor circuitry may damage the contacts within the system relay. Follow this step 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.
Use the scan tool in order to perform an ABS Function Test.
Does DTC C0266 set?
--
Go to Step 7
Go to Step 3

3
Does DTC C0265 set?
--
Go to Step 4
Go to Diagnostic Aids

4
Turn OFF the ignition.
Disconnect from the EBCM, the harness connector containing the battery positive voltage circuit.
Connect a test lamp between the battery positive voltage circuit and a good ground.
Does the test lamp illuminate?
--
Go to Step 6
Go to Step 5

5
Repair the open in the battery positive voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you complete the repair?
--
Go to Step 11
--

6
Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
--
Go to Step 11
Go to Step 7

7

Important
It may be necessary to separate the EBCM from the BPMV to gain access to the pump motor pigtail connector. If so, refer to Electronic Brake Control Module (EBCM) Replacement .


Disconnect from the EBCM, the ABS pump motor pigtail connector.
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 8
Go to Step 10

8
Use a DMM in order to measure the resistance between the high side of the pump motor and a good ground.

Does the resistance measure less than the specified value?
0L
Go to Step 10
Go to Step 9

9

Important
Use the scan tool in order 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 11
--

10

Important
Use the scan tool in order to 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 Brake Pressure Modulator Valve (BPMV) Replacement .

Did you complete the replacements?
--
Go to Step 11
--

11
Use the 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 2
System OK
 
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