Any one know what code C0265, unknown diagnostic trouble code $29 means?


GM Confussed:
2000 Silverado 5.3
I am a new user.  Is there any training help available?

The C0265 code is a generic DTC and points to an electrical problem in the ABS; specifically to the EBCM (Electronic Brake Control Module).  This DTC will not illuminate the MIL.  I have the same truck and got this code once.  The EBCM is located forward of the gas tank under the vehicle on the driver's side and is attached to the vehicle frame.  It is directly under the driver's seat.  I simply unplugged the two connectors from the module,cleaned them up, and reconnected.  The problem hasn't reappeared again.

I'm not sure what the unknown DTC $29 is.  It may be a GM enhanced code that you'll need a code reader with enhanced code reading capabilities to read this code.  I would guess it is also related to the ABS like the first one.  The ScanXL and PCMSCAN available on this site has this capability if you also purchase the GM Enhanced product along with it.  You will also need an interface component such as OBDLink to communicate between the vehicle and the software.  There's other software and interface configurations out there as well but that's your decision what to buy.  Just steer away from a cloned ELM327 interface device (if it comes from China, beware).  Anything you purchase that includes the manufacturer's enhanced code reading capabilities will be more expensive than anything that only reads generic codes.

As for training, for an auto hobbiest such as myself, the internet is rich with information to research what you want to know.  That's how I've done things.  Just Google OBD II and start there.  Rather than taking my truck to a mechanic, I research the problems online first.  I have a shop with tools, so if it's something I can do myself, I fix it.  To help I've purchased PC software and other online subscriptions to assist me in the diagnostics.  For the most complicated fixes, I take to a mechanic so it gets done correctly and I don't mess things up.  Other than information you find on this Forum and others, there's no real training other than attending a trade school or taking online automotive courses which cost more time and money.

I hope this helps you.


$29 is the address of the ABS module, I'm not sure why it would show as a DTC.

I have looked through the files GM sent us, the description for that code is "EBCM Motor Relay Circuit". I have added it to our database.

#04-05-25-002E: ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Module (Reground EBCM Ground) - (Mar 11, 2009)

Subject: ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Module (Reground EBCM Ground)

Models: 2004-2007 Buick Rainier

 2002-2006 Cadillac Escalade, Escalade EXT

 2003-2006 Cadillac Escalade ESV

 1999-2007 Chevrolet Silverado Classic

 2000-2006 Chevrolet Suburban, Tahoe

 2002-2006 Chevrolet Avalanche

 2002-2007 Chevrolet TrailBlazer, TrailBlazer EXT

 2003-2006 Chevrolet SSR

 1999-2007 GMC Sierra Classic

 2000-2006 GMC Yukon, Yukon Denali, Yukon XL

 2002-2007 GMC Envoy, Envoy XL, Sierra Denali Classic

 2004-2005 GMC Envoy XUV

 2002-2004 Oldsmobile Bravada


This bulletin is being revised to add step 2 to the procedure and update the Parts and Warranty Information. Please discard Corporate Bulletin Number 04-05-25-002D (Section 05 -- Brakes).


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.

A poor connection at the EBCM ground is causing unnecessary replacement 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

Important: Do not replace the brake module to correct this condition. Perform the following repair before further diagnosis of the EBCM.

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.
If the original fastener has a welded on nut, remove the nut from the frame, and if required, enlarge the bolt hole to accommodate the new bolt and nut.
Clean the area, front and back, using a tool such as a *3M™ Scotch-Brite™ Roloc disc or equivalent.
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 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.

*We believe this source and their products to be reliable. There may be additional manufacturers of such products/materials. General Motors does not endorse, indicate any preference for or assume any responsibility for the products or material from this firm or for any such items that may be available from other sources.

Parts Information
Part Number

(in Canada, 10952414)
 Rubberized Undercoating -- Paintable
 **3M™ Scotch-Brite™ Roloc disc

Part Number

(in Canada, 10952414)
 Rubberized Undercoating -- Paintable
 **3M™ Scotch-Brite™ Roloc disc

**This product is currently available from 3M. To obtain information for your local retail location, please call 3M at 1-800-364-3577.

Warranty Information
For vehicles repaired under warranty, use:

Labor Operation
 Labor Time
 Ground Repair - EBCM Ground
 0.3 hr
*This is a unique labor operation number for bulletin use only. The number will not be published in the Labor Time Guide.
GM bulletins are intended for use by professional technicians, NOT a "do-it-yourselfer".  They are written to inform these technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle.  Properly trained technicians have the equipment, tools, safety instructions, and know-how to do a job properly and safely.  If a condition is described, DO NOT assume that the bulletin applies to your vehicle, or that your vehicle will have that condition.  See your GM dealer for information on whether your vehicle may benefit from the information.


DTC C0265 or C0266 and C065 C066 EBCM Relay Circuit
Circuit Description
The system relay supplies battery voltage to all six valve solenoids. The EBCM applies the ground(s) needed for solenoid activation. The low side of each solenoid coil has a feedback circuit to the EBCM. When the relay is commanded off, feedback voltage is low. When the relay is commanded on and the solenoid is commanded off, feedback voltage is high.

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 low feedback voltage from all of the valve solenoids when the relay is commanded on and the solenoids are commanded off.

The EBCM detects high feedback voltage from all of the valve solenoids when the relay is commanded off.

Action Taken When the DTC Sets
    •  The ABS and BRAKE indicators are commanded on.

    •  The ABS and DRP are disabled for the remainder of the ignition cycle.

    •  The EBCM aborts all other self-tests for components that are powered by the system relay (DTC C0265 only).

Conditions for Clearing the DTC
    •  The condition(s) responsible for setting the DTC are no longer present.

    •  A scan tool is used in order to clear the DTC.

Diagnostic Aids
An intermittent DTC C0265 may be caused by a problem in the battery positive voltage circuit wiring or connection to the EBCM. Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions and Poor Connections , Wiring Repairs and Connector Repairs in Wiring Systems.

An intermittent DTC C0266 can be set by several different internal EBCM problems. Replace the EBCM if DTC C0266 continues to set intermittently.

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

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

Schematic Reference: Antilock Brake System Schematics
 Did you perform the ABS Diagnostic System Check?
 Go to Step 2
 Go to Diagnostic System Check
 Use a scan tool in order to clear the DTC(s).
Use the scan tool in order to perform an ABS Relay Test.
Does DTC C0266 set?
 Go to Step 7
 Go to Step 3
 Does DTC C0265 set?
 Go to Step 4
 Go to Diagnostic Aids
 Turn the ignition OFF.
Disconnect from the EBCM, the harness connector which contains the battery positive voltage circuit.
Connect a test lamp between the battery positive voltage circuit (at the harness connector) and a good ground.
Does the test lamp illuminate?
 Go to Step 6
 Go to Step 5
 Repair the open in the battery positive voltage circuit. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?
 Go to Step 8
 Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?
 Go to Step 8
 Go to Step 7
 Important: Use the scan tool in order to perform the Tire Size Calibration procedure.

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

Did you complete the replacement?
 Go to Step 8
 Use the scan tool in order to clear the DTC.
Operate the vehicle within the Conditions for Running the DTC.
Does the DTC set?
 Go to Step 2
 System OK


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