Mol
Member
My 4wd works just fine, but I have had a "service 4wd" message for quite some time, only recently got around to scanning it.
It's showing the following 3 transfer case codes:
U1301 - Class 2 communications circuit low voltage
U1000 - Class 2 serial communications problem
B0790 - Transfer case neutral indicator circuit
Any ideas? I'm finding very minimal information from google searches
I also have an ABS code being thrown as of about a week ago, with a strange symptom. I started the car one morning, and a loud humm was audible from within the cab, ABS light and parking light came on. Cycled the ignition a few times, set the parking brake, pumped the brake pedal and the humming persisted. Upon a quick inspection, I determined it was the ABS pump running constantly. I pulled the ABS fuse under the hood to kill the pump. Tried plugging it back in and the problem had not gone away. Scanned it and found the following code:
C0265 - EBCM Motor Relay Circuit
I searched for an ABS relay, but couldn't find one. Am I overlooking it, or misinterpreting the code? Any suggestions are appreciated!
It's a 2004 YXL K2500 6.0L, by the way
---------- Post added at 10:31 PM ---------- Previous post was at 08:58 PM ----------
Managed to track this bulletin down for the faulty EBCM:
Subject: ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Moduel (Reground EBCM Ground) #04-05-25-002D - (06/14/2007)
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 Chevolet 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 update model years. Please discard Corporate Bulletin Number 04-05-25-002C (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.
Parts Information
FULL-SIZE TRUCKS, SUVs AND H2
Part Number
Description
11588564
Bolt
15650962
Washer
15672934
Nut
12378398
(in Canada, 10952414)
Rubberized Undercoating -- Paintable
MIDSIZE SUVs
Part Number
Description
11517555
Bolt
15650961
Washer
11503749
Nut
12378398
(in Canada, 10952414)
Rubberized Undercoating -- Paintable
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation
Description
Labor Time
N9502
Ground Repair - EBCM Ground
0.2 hr
---------- Post added at 10:32 PM ---------- Previous post was at 10:31 PM ----------
And this flow chart:
DTC C0265 or C0266 and C065 or C066
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
• Low system voltage
• Open ground at the EBCM
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.
Check ground G110 for an open or a high resistance.
Check the EBCM power supply for an intermittent open.
C0265
Thoroughly inspect connections and circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions 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
It's showing the following 3 transfer case codes:
U1301 - Class 2 communications circuit low voltage
U1000 - Class 2 serial communications problem
B0790 - Transfer case neutral indicator circuit
Any ideas? I'm finding very minimal information from google searches
I also have an ABS code being thrown as of about a week ago, with a strange symptom. I started the car one morning, and a loud humm was audible from within the cab, ABS light and parking light came on. Cycled the ignition a few times, set the parking brake, pumped the brake pedal and the humming persisted. Upon a quick inspection, I determined it was the ABS pump running constantly. I pulled the ABS fuse under the hood to kill the pump. Tried plugging it back in and the problem had not gone away. Scanned it and found the following code:
C0265 - EBCM Motor Relay Circuit
I searched for an ABS relay, but couldn't find one. Am I overlooking it, or misinterpreting the code? Any suggestions are appreciated!
It's a 2004 YXL K2500 6.0L, by the way
---------- Post added at 10:31 PM ---------- Previous post was at 08:58 PM ----------
Managed to track this bulletin down for the faulty EBCM:
Subject: ABS Light On, DTCs C0265, C0201, U1041 Set and/or Loss of Communication with Brake Moduel (Reground EBCM Ground) #04-05-25-002D - (06/14/2007)
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 Chevolet 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 update model years. Please discard Corporate Bulletin Number 04-05-25-002C (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.
Parts Information
FULL-SIZE TRUCKS, SUVs AND H2
Part Number
Description
11588564
Bolt
15650962
Washer
15672934
Nut
12378398
(in Canada, 10952414)
Rubberized Undercoating -- Paintable
MIDSIZE SUVs
Part Number
Description
11517555
Bolt
15650961
Washer
11503749
Nut
12378398
(in Canada, 10952414)
Rubberized Undercoating -- Paintable
Warranty Information
For vehicles repaired under warranty, use:
Labor Operation
Description
Labor Time
N9502
Ground Repair - EBCM Ground
0.2 hr
---------- Post added at 10:32 PM ---------- Previous post was at 10:31 PM ----------
And this flow chart:
DTC C0265 or C0266 and C065 or C066
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
• Low system voltage
• Open ground at the EBCM
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.
Check ground G110 for an open or a high resistance.
Check the EBCM power supply for an intermittent open.
C0265
Thoroughly inspect connections and circuitry that may cause an intermittent malfunction. Refer to Testing for Intermittent Conditions 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
