GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2000 🢒 Blazer - 4WD 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0269 or C0274 and C069 or C074 Excessive Dump/Isolation Time

DTC C0269 or C0274 and C069 or C074 Excessive Dump/Isolation Time 310 ABS

Circuit Description

C0269

The EBCM commands the dump valve solenoid on in order to open the dump valve and decrease the hydraulic pressure applied to a brake circuit.

C0274

The EBCM commands the isolation valve solenoid on in order to close the isolation valve and prevent the application of additional hydraulic pressure to a brake circuit.

Conditions for Running the DTC
    • The ignition is ON.
    • The vehicle is experiencing an ABS event.

Conditions for Setting the DTC

C0269

The EBCM microprocessor commands one or more dump valve solenoids on for 9 consecutive seconds.

C0274

The EBCM microprocessor commands one or more isolation valve solenoids on for 255 consecutive seconds.

Action Taken When the DTC Sets

C0269

    • The ABS indicator is commanded on.
    • If the dump command is directed to a front wheel, the front ABS is disabled for the remainder of the ignition cycle.
    • If the dump command is directed to the rear wheels, the ABS is disabled for the remainder of the ignition cycle. In this situation, the BRAKE indicator is also commanded on.

C0274

    • The ABS and BRAKE indicators are commanded on.
    • The ABS and DRP are disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

    • Repair the condition(s) responsible for setting the DTC.
    • Use a scan tool in order to clear the DTC.

Diagnostic Aids

The most likely cause of DTC C0269 or DTC C0274 is a mechanical failure that causes a wheel to lock and remain locked. The DTC(s) may also be set, conceivably, by activating the ABS on surfaces that are nearly impossible to get traction on (i.e.; sheet ice). In either of these situations, diagnosis of the ABS system is not necessary.

Test Description

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

  1. Using the scan tool to perform solenoid tests determines if there is a mechanical malfunction(s) inside the BPMV (i.e.; a dump valve(s) stuck closed or an isolation valve(s) stuck open). Perform Dump Valve Tests for DTC C0269 or Isolation Valve Tests for DTC C0274.

Step

Action

Value(s)

Yes

No

1

Did you perform the ABS Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Install a scan tool.
  2. Use a scan tool in order to clear the DTC.
  3. Select the 4WAL 3 sensor Special Functions menu on the scan tool and perform the necessary Solenoid Test(s). Refer to Scan Tool Diagnostics .

Does the Solenoid Test(s) show the system to be functioning normally?

--

System OK

Go to Step 3

3

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

Did you complete the replacement?

--

System OK

--

DTC C0269 or C0274 and C069 or C074 Excessive Dump/Isolation Time 325 ABS

Circuit Description

C0269

The EBCM commands the dump valve solenoid on in order to open the dump valve and decrease the hydraulic pressure applied to a brake circuit.

C0274

The EBCM commands the isolation valve solenoid on in order to close the isolation valve and prevent the application of additional hydraulic pressure to a brake circuit.

Conditions for Running the DTC
    • The ignition is ON.
    • The vehicle is experiencing an ABS event.

Conditions for Setting the DTC

C0269

The EBCM microprocessor commands one or more dump valve solenoids on for 9 consecutive seconds.

C0274

The EBCM microprocessor commands one or more isolation valve solenoids on for 255 consecutive seconds.

Action Taken When the DTC Sets

C0269

    • The ABS indicator is commanded on.
    • If the dump command is directed to a front wheel, the front ABS is disabled for the remainder of the ignition cycle.
    • If the dump command is directed to the rear wheels, the ABS and DRP are disabled for the remainder of the ignition cycle. In this situation, the BRAKE indicator is also commanded on.

C0274

    • The ABS and BRAKE indicators are commanded on.
    • The ABS and DRP are disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

    • Repair the condition(s) responsible for setting the DTC.
    • Use a scan tool in order to clear the DTC.

Diagnostic Aids

The most likely cause of DTC C0269 or DTC C0274 is a mechanical failure that causes a wheel to lock and remain locked. The DTC(s) may also be set, conceivably, by activating the ABS on surfaces that are nearly impossible to get traction on (i.e.; sheet ice). In either of these situations, diagnosis of the ABS system is not necessary.

Test Description

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

  1. Using the scan tool to perform solenoid tests determines if there is a mechanical malfunction(s) inside the BPMV (i.e.; a dump valve(s) stuck closed or an isolation valve(s) stuck open). Perform Dump Valve Tests for DTC C0269 or Isolation Valve Tests for DTC C0274.

Step

Action

Value(s)

Yes

No

1

Did you perform the ABS Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check

2

  1. Install a scan tool.
  2. Use a scan tool in order to clear the DTC.
  3. Select the 4WAL 3 sensor Special Functions menu on the scan tool and perform the necessary Solenoid Test(s). Refer to Scan Tool Diagnostics .

Does the Solenoid Test(s) show the system to be functioning normally?

--

System OK

Go to Step 3

3

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

Did you complete the replacement?

--

System OK

--