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Dan
Dan, Auto Technician
Category: Chevy
Satisfied Customers: 3490
Experience:  GM Mark of Excellence/ Service Guild Participant with 13 years experience, ASE Master Certified
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2001 Chevy Blazer: 4wd..ABS light..brake light..the connector

Resolved Question:

2001 Chevy Blazer 4wd, ABS light and parking brake light intermittent code C0265, so far I have spray cleaned the connectors, cleaned and wire wheeled the ABS ground at the rad support also checked continuity, ran a wire from the bat neg to the rad support ground still same there are 4 bat ground wires, I have cleaned one the others are tough to get to without a lift, finnally my question if I run a wire from the bat neg to just before the connector and splice it in that should give me a good ground and knock out the lights correct?
Submitted: 5 years ago.
Category: Chevy
Expert:  Dan replied 5 years ago.
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.

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 the following:

    • Testing for Intermittent Conditions and Poor Connections

    • Testing for Electrical Intermittents

    • Connector Repairs

    • Wiring Repairs

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: Antilock Brake System Schematics

Connector End View Reference: Antilock Brake System 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 Conditions 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 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 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 Replacement and Brake Pressure Modulator Valve 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

Customer: replied 5 years ago.
I have gotten that info at http://www.blazerforum.com/m_147323/tm.htm will a direct ground temp fix the problem?
Expert:  Dan replied 5 years ago.
It depends. If the internal resistance to the EBCM is not within spec the fault will remain and the problem can only be solved by replacing the EBCM.
Dan, Auto Technician
Category: Chevy
Satisfied Customers: 3490
Experience: GM Mark of Excellence/ Service Guild Participant with 13 years experience, ASE Master Certified
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