DTC C0269 or C0274 and C069 or C074 Excessive Dump/Isolation Time. GMC Truck Savana 2000

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 2000 🢒 Savana 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C0269 or C0274 and C069 or C074 Excessive Dump/Isolation Time

Circuit Description

C0269

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

C0274

The EBCM commands an 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 commands a dump valve solenoid(s) on for 9 consecutive seconds.

C0274

The EBCM commands an isolation valve solenoid(s) 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, all ABS function is disabled for the remainder of the ignition cycle.

C0274

•	The ABS indicator is commanded on.

•	The ABS is disabled for the remainder of the ignition cycle.

Conditions for Clearing the DTC

•	The condition(s) responsible for setting the DTC is no longer present.

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

Ensure proper operation of the base brake system. The most likely cause of DTC C0269 or DTC C0274 is a mechanical failure that causes a wheel(s) to lock and remain locked. The DTC(s) may also set, conceivably, when the ABS is activated on surfaces that are nearly impossible to get traction on (i.e.; sheet ice). If the DTC sets within these conditions, diagnosis of the ABS system is not necessary.

Test Description

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

Using the scan tool in order to perform an ABS Function Test while applying firm and steady pressure to the brake pedal and observing how the pedal reacts 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).

Step

Action

Value(s)

Yes

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to Diagnostic System Check

Install a scan tool.
Use the scan tool in order to clear the DTC(s).
Use the scan tool in order to perform an ABS Function Test while applying firm and steady pressure to the brake pedal. Observe the brake pedal and ensure that the pedal reacts as follows (time values in the list below are approximate):

3.1.	The pump motor activates (0.5 seconds).

3.2.	The pedal drops to the floor (2 seconds).

3.3.	The pedal pumps up (2 seconds).

3.4.	The pedal drops approximately 1.25 cm (1/2 inch) and then holds (1 second).

3.5.	Steps 3.2, 3.3 and 3.4 repeat.

3.6.	Steps 3.2, 3.3 and 3.4 repeat.

3.7.	Step 3.2 repeats.

3.8.	Step 3.3 repeats.

3.9.	Step 3.2 repeats.

3.10.

Step 3.3 repeats.

Does the brake pedal react as described when the Function Test is performed?

Go to Diagnostic Aids

Go to Step 3

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

Did you complete the replacement?

Go to Step 4

Use the scan tool in order to perform an ABS Function Test while applying firm and steady pressure to the brake pedal. Observe the brake pedal and ensure that the pedal reacts as described in step 2.

Does the brake pedal react as described in step 2 when the Function Test is performed?

System OK

Go to Step 2