Antilock Braking System (ABS)

DTC 61 Pump Motor Circuit Test (part 1 Of 3):

DTC 61 Pump Motor Circuit Test (part 2 Of 3):

DTC 61 Pump Motor Circuit Test (part 3 Of 3):

DTC 61 Pump Motor Circuit Test:

CIRCUIT OPERATION
When the EBCM/EBTCM grounds terminal 15, the pump relay contacts close applying voltage to the pressure modulator valve (PMV) 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.

When the pump motor runs during ABS braking, the PMV assembly reservoir is replenished and fluid pressure is applied to the master cylinder. This causes the brake pedal to rise gradually. The pump motor runs until the brake pedal sufficiently rises to close the TCC/antilock brake switch.

During traction control mode, after the front hydraulic circuits are isolated, the pump motor runs to increase brake fluid pressure in these circuits. The increased pressure is directed to the slipping wheel through the PMV assembly's front inlet and outlet valves. This causes the brakes to be applied, reducing wheel spin at the slipping wheel. Traction control is disabled as soon as the brakes are manually applied.

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 terminals 49 and 31.

FAILURE CONDITIONS
When the EBCM/EBTCM grounds terminal 15, DTC 61 sets when the EBCM/EBTCM determines the frequency between EBCM/EBTCM terminals 31 and 49 is not between 70-150 Hz. The EBCM/EBTCM recognizes this condition only during ABS braking requiring pump motor operation, traction control mode (when equipped), and during the EBCM/EBTCM self-check which occurs when the vehicle reaches 11 km/h (7 mph). Therefore, be sure to test drive vehicle, after clearing the DTC to assure correct diagnosis.

DTC 61 also sets when the pump motor runs all the time (i.e. EBCM/EBTCM sees proper voltage between terminals 31 and 49 without grounding terminal 15).


Possible Causes
^ Open in CKT 1450, 864, 854, 1633, 1292, 1293 or 1446.
^ Short to ground in CKT 864, 854, 1292, 1293, or 642.
^ ABS pump relay fails "open" or "engaged."