Circuit Description
| • | When the EBCM/EBTCM grounds terminal 15, the pump relay contacts close. The closed contacts apply voltage to the BPMV assembly's pump motor. The EBCM/EBTCM turns ON the pump motor during most ABS braking conditions and, when equipped, during all traction control conditions. |
| • | During ABS braking, when the pump motor is running, the BPMV reservoir replenishes and pressurizes the master cylinder. This causes the brake pedal to rise gradually. The pump motor will run until the brake pedal rises sufficiently in order to close the TCC/antilock brake switch. |
| • | During traction control mode, after the front hydraulic circuits are isolated, the pump motor increases fluid pressure in these circuits. The increased pressure is directed to the slipping wheel through the BPMV's front inlet and outlet valves. This pressure causes the brakes to be applied, reducing wheel spin at the slipping wheel. Traction control is disabled as soon as the brakes are applied manually. |
| • | The EBCM/EBTCM monitors pump motor operation via the pump motor run sensor. When the pump is operating, voltage is induced into the sensor's coil and the EBCM/EBTCM monitors this voltage at terminal 49 and terminal 31. |
Conditions for Setting the DTC
| • | When the EBCM/EBTCM grounds terminal 15, DTC C1261 sets if the EBCM/EBTCM determines that the frequency between EBCM/EBTCM terminals 31 and 49 is less than 160 Hz. |
| • | The EBCM/EBTCM recognizes this condition only while ABS braking during the following actions: |
| - | Pump motor operation |
| - | Traction control mode (when equipped) |
| - | The EBCM/EBTCM self-check which occurs when the vehicle reaches 20 km/h (12 mph) |
| • | Test drive the vehicle after clearing the DTC in order to ensure the correct diagnosis. |
| • | DTC C1261 also sets when the pump motor runs continuously (when the EBCM/EBTCM sees proper voltage between terminal 31 and terminal 49 without grounding terminal 15). |
Action Taken When the DTC Sets
| • | DTC C1261 is stored. |
| • | The ABS is disabled. |
| • | The ANTILOCK indicator lamp is turned on. |
Conditions for Clearing the DTC
The DTC will clear under the 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 of this malfunction:
| • | An open in any of the following circuits: |
| - | CKT 1450 |
| - | CKT 1451 |
| - | CKT 864 |
| - | CKT 854 |
| - | CKT 1633 |
| - | CKT 1292 |
| - | CKT 1293 |
| • | A short to the ground in any of the following circuits: |
| - | CKT 864 |
| - | CKT 854 |
| - | CKT 1292 |
| - | CKT 1293 |
| - | CKT 542 |
| • | An ABS pump relay failed to open, engaged, or points with high resistance. |
| • | An ABS main relay failure |
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
1 | Was the Diagnostic System Check performed? | -- | Go to Diagnostic System Check | |
2 | Turn the ignition switch to the RUN position. Does the BPMV pump motor run continuously? | -- | ||
3 | Remove the ABS pump relay. Does the pump motor stop running? | -- | ||
4 |
Is the voltage within the specified range? | Battery Voltage | ||
5 |
Does the pump motor run? | -- | ||
6 |
Is the resistance equal to the specified value? | OL (Infinite) | ||
7 | Measure the resistance between BPMV pigtail connector C2 terminal D and F. Is the resistance within the specified range? | 10-40 ohms | ||
8 |
Is the resistance less than the specified value? | 2 ohms | ||
9 | Measure the resistance between the J 38716 pinout box terminals 31 and 49. Is the resistance within the specified range? | 10-40 ohms | ||
10 | Measure the resistance between the J 38716 pinout box terminals 49 and 1. Is the resistance less than the specified value? | 2 ohms | ||
11 | Measure the resistance between the J 38716 pinout box terminals 31 and 1. Is the resistance less than the specified value? | 2 ohms | ||
12 |
Is the frequency greater than the specified value? | 160 Hz | ||
13 |
Is the voltage within the specified range? | Battery Voltage | ||
14 |
Is the voltage within the specified range? | Battery Voltage | ||
15 | Connect a fused jumper between the ABS pump relay harness terminals 30 and 87. Does the pump motor run? | -- | ||
16 |
Disconnect the BPMV connector C2. Is the voltage within the specified range? | Battery Voltage | ||
17 | Measure the voltage between BPMV harness connector C2 terminal A and E. Is the voltage within the specified range? | Battery Voltage | ||
18 |
Is the resistance less than the specified value? | 2 ohms | ||
19 | Connect the fused jumpers between the J 38716 pinout box terminals 15 and 1, and between terminals 34 and 1. Does the pump motor run? | -- | ||
20 |
Measure the resistance between pinout box terminal 15 and the ABS pump relay harness connector terminal 86. Is the resistance less than the specified value? | 2 ohms | ||
21 | Remove and inspect the ABS pump motor fuse of the engine compartment fuse block. Is the fuse open? | -- | Go to Diagnostic System Check | |
22 |
Is the resistance equal to the specified value? | OL (Infinite) | ||
23 |
Is the resistance equal to the specified value? | OL (Infinite) | ||
24 | Repair the short to voltage in CKT 864 Is the repair complete? | -- | Go to Diagnostic System Check | -- |
25 | 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 | -- |
26 |
Is the repair complete? | -- | Go to Diagnostic System Check | -- |
27 | Repair the short to ground in CKT 1292. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
28 | Repair the short to ground in CKT 1293. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
29 | Repair the open or high resistance in CKT 1633. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
30 | 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 | -- |
31 | Repair the open or high resistance in CKT 864. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
32 | Repair the open or high resistance in CKT 1450. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
33 | Repair the open or high resistance in CKT 854. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
34 | Repair the short to ground in CKT 542. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
35 | Repair the short to ground in CKT 864. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
36 | Replace the ABS pump relay. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
37 | Repair the short to voltage in CKT 854. Refer to Wiring Repairs in Wiring Systems. Is the repair complete? | -- | Go to Diagnostic System Check | -- |
38 | Replace the EBCM/EBTCM. Refer to Electronic Brake and Traction Control Module Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- |
39 | Replace the BPMV. Refer to Brake Pressure Modulator Valve Replacement . Is the repair complete? | -- | Go to Diagnostic System Check | -- |
