GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 1998 🢒 Riviera 🢒 Brakes 🢒 Antilock Brake System 🢒 DTC C1274 BPMV Pressure Switch Circuit Malfunction

Object Number: 406531 Size: MF
ABS Components
Cell 44: ABS/TCS Switch, Isolation Valve Solenoids, and PCM
Cell 10: F/PMP, HZRD/STOP and INTR LP Fuses
Cell 110: Turn/Hazard Switch and Stoplamp/BTSI Switch
Cell 110: Turn/Hazard Switch and Stoplamp/BTSI Switch

Circuit Description
    • The pressure switch monitors primary brake system pressure. The switch, normally closed, opens when the brakes are applied and pressure exceeds 700 kPa (101 psi).
    •  If the brakes are applied manually during traction control mode, the BPMV pressure switch input, along with the brake switch input, signal the EBTCM to disable traction control and allow manual braking. The pressure switch is part of the BPMV assembly and is not serviceable.

Conditions for Setting the DTC

DTC C1274 sets when the EBTCM detects an open or short to ground in the BPMV pressure switch circuitry.

Action Taken When the DTC Sets

The following actions are taken when the DTC sets:

    • DTC C1274 is stored.
    • TCS is disabled.
    • The TRACTION OFF indicator lamp is turned ON.

Conditions for Clearing the DTC

The DTC will clear under following conditions:

    • Conditions for the malfunction are no longer present. Use the scan tool Clear DTCs function.
    • 100 ignition switch key cycles have passed without detecting any malfunctions

Diagnostic Aids
    • The following conditions are other possible causes for this malfunction:
       - The TCC/antilock switch circuit is open or shorted to voltage
       - The BPMV fluid level switch circuit is open or shorted to voltage
       - The ABS pump motor pressure switch circuit is open or shorted to voltage
    • Perform a thorough inspection of the wiring and the connectors.
        Failure to carefully inspect wiring may result in a misdiagnosis. A misdiagnosis may result in replacing parts without repairing the malfunction.
    • DTC C1274 may also store along with DTC C1245. Diagnose DTC C1245 first before diagnosing DTC C1274.

Step

Action

Value(s)

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step  2

Go to Diagnostic System Check

2
  1. Turn the ignition switch to the OFF position.
  2. Remove and inspect the rear fuse block HZRD/STOP fuse.

Is the fuse open?

--

Go to Step  17

Go to Step  3

3
  1. Disconnect the stoplamp/BTSI switch harness connector.
  2. Using the J 39200 set to DC scale, measure the voltage between the stoplamp/BTSI switch harness connector terminal A and ground.

Is the voltage within the specified range?

Battery Voltage

Go to Step  4

Go to Step  18

4
  1. Press and hold the brake pedal.
  2. Use the J 39200 set to ohms in order to measure the resistance between stoplamp/BTSI switch terminals A and B.

Is the resistance less than the specified value?

2  ohms

Go to Step  6

Go to Step  5

5
  1. Reconnect the stoplamp/BTSI switch connector.
  2. Check for proper stoplamp/BTSI switch adjustment. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.

Is the brake switch properly adjusted?

--

Go to Step  19

Go to Step  20

6
  1. Disconnect the EBTCM harness connector.
  2. Install the J 38716 pinout box. Measure the resistance between the J 38716 pinout box terminal 1 and the ground.

Is the resistance less than the specified value?

2  ohms

Go to Step  7

Go to Step  21

7
  1. Turn the ignition switch to the RUN position.
  2. Use the J 39200 set to DC scale in order to measure the voltage between J 39200 pinout box terminals 1 and 32.

Is the voltage greater than the specified value?

1 V

Go to Step  22

Go to Step  8

8
  1. Press and hold the brake pedal.
  2. Measure the voltage between the J 39200 pinout box terminals 1 and 32.

    3. Is the voltage within the specified range?

Battery Voltage

Go to Step  9

Go to Step  23

9
  1. Turn the ignition switch to the OFF position.
  2. Disconnect the BPMV connector C1.
  3. Measure the resistance between BPMV connector (BPMV side) terminal 11 and the BPMV case.

Is the resistance equal to the specified value?

OL (Infinite)

Go to Step  10

Go to Step  28

10

Measure the resistance between BPMV connector terminals 11 and 12 (BPMV side).

Is the resistance less than the specified value?

2 ohms

Go to Step  11

Go to Step  28

11
  1. Press and hold the brake pedal.
  2. Measure the resistance between BPMV connector terminals 11 and 12 (BPMV side).

Is the resistance equal to the specified value?

OL (Infinite)

Go to Step  12

Go to Step  28

12

Measure the resistance between pinout box terminal 13 and BPMV connector terminal 11 (harness side).

Is the resistance less than the specified value?

2  ohms

Go to Step  13

Go to Step  24

13

Measure the resistance between pinout box terminal 26 and BPMV connector terminal 12 (harness side).

Is the resistance less than the specified value?

2 ohms

Go to Step  14

Go to Step  25

14
  1. Disconnect the BPMV fluid level switch and the brake switch connectors.
  2. Turn the ignition switch to the RUN position.
  3. Measure the voltage between J 39200 pinout box terminals 1 and 5.
  4. Measure the voltage between pinout box terminals 1 and 8.
  5. Measure the voltage between J 39200 pinout box terminals 1 and 13.
  6. Measure the voltage between J 39200 pinout box terminals 1 and 26.

Was the voltage greater than the specified value on any of the measurements?

1 V

Go to Step  26

Go to Step  15

15
  1. Turn the ignition to the OFF position.
  2. Disconnect the negative battery cable. Refer to

    Caution: Unless directed otherwise, the ignition and start switch must be in the OFF or LOCK position, and all electrical loads must be OFF before servicing any electrical component. Disconnect the negative battery cable to prevent an electrical spark should a tool or equipment come in contact with an exposed electrical terminal. Failure to follow these precautions may result in personal injury and/or damage to the vehicle or its components.

    in General Information.
  3. Measure the resistance between J 39200 pinout box terminals 1 and 5.
  4. Measure the resistance between J 39200 pinout box terminals 1 and 8.
  5. Measure the resistance between J 39200 pinout box terminals 1 and 13.
  6. Measure the resistance between J 39200 pinout box terminals 1 and 26.

Is the resistance equal to the specified on any of the measurements?

OL (Infinite)

Go to Step  16

Go to Step  27

16
  1. Reconnect all connectors
  2. Turn the ignition switch to the RUN position.
  3. Using the scan tool, clear the DTCs.
  4. Test drive the vehicle.

Does DTC C1274 reset?

--

Go to Step  29

Go to Diagnostic System Check

17
  1. Repair the short to ground in CKT 140 or CKT 17. Refer to Wiring Repairs in Wiring Systems.
  2. Replace the HZRD/STOP fuse.

Is the repair complete?

--

Go to Diagnostic System Check

--

18

Repair the open or high resistance in CKT 140. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

19

Replace the brake switch. Refer to Stop Lamp Switch Replacement in Hydraulic Brakes.

Is the repair complete?

--

Go to Diagnostic System Check

--

20

Adjust the brake switch. Refer to Stop Lamp Switch Adjustment in Hydraulic Brakes.

Is the repair complete?

--

Go to Diagnostic System Check

--

21

Repair the open or high resistance in CKT 1451. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

22

Repair the short to voltage in CKT 17. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

23

Repair the open or high resistance in CKT 17. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

24

Repair the open or high resistance in CKT 1659. Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

25

Repair the open or high resistance in CKT 853. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?

--

Go to Diagnostic System Check

--

26

Repair the short to voltage in any circuit that measured more than 1 V. Refer to Wiring Repairs in Wiring Systems. Is the repair complete?

--

Go to Diagnostic System Check

--

27

Repair the short to ground in any circuits that did not measure OL (infinite). Refer to Wiring Repairs in Wiring Systems.

Is the repair complete?

--

Go to Diagnostic System Check

--

28

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

Is the repair complete?

--

Go to Diagnostic System Check

--

29

Replace the EBTCM. Refer to Electronic Brake and Traction Control Module Replacement .

Is the repair complete?

--

Go to Diagnostic System Check

--