C1261

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 WITH THE DTC SETS
^ DTC C1 261 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 ground in any of the following circuits:
^ CKT 864
^ CKT 854
^ CKT 1292
^ CKT 1293
^ CKT 542
^ An ABS pump relay failed open, engaged, or point with high resistance.
^ A main relay failure

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DTC C1261 PUMP MOTOR RUN MALFUNCTION