Pump Circuit Failure

PUMP CIRCUIT FAILURE





For a complete wiring diagram Consult Diagrams/Electrical.

- When Monitored:
Ignition on. The CAB commands the pump on at 20 km/h (12 mph) to check its operation, if the brake switch is not applied. If the brake is applied, the test will run at 40 km/h (25 mph).

- Set Condition:
The DTC is stored when the CAB detects: 1) Improper voltage decay after the pump was turned off. 2) Pump not energized by the CAB, but voltage is present for 3.5 seconds. 3) Pump is turned on by the CAB, but without sufficient voltage to operate it.





Diagnostic Test

1. CHECK FOR A DTC PUMP CIRCUIT FAILURE
NOTE: This DTC must be active for the results of this test to be valid.

Turn the ignition on.
With the scan tool, record and erase DTCs.
Cycle the ignition switch from off to on.
Road test the vehicle over 40 km/h (25 mph).

NOTE: The CAB must sense ALL wheels at 25 km/h (15 mph) before it will extinguish the ABS indicators.

With the scan tool, read DTCs.
Does the scan tool display: PUMP CIRCUIT FAILURE?

Yes

- Go To 2

No

- Perform the ABS Intermittent Condition diagnostic procedure. ABS Intermittent Condition Test
- Perform ABS VERIFICATION TEST. ABS Verification Test

2. CAB - PUMP MOTOR RUNNING CONTINUOUSLY
Turn the ignition off.
Turn the ignition on.
Monitor the ABS Pump Motor for continuous operation.
Is the ABS Pump Motor running continuously?

Yes

- Replace the Anti-Lock Brake Controller (CAB).
- Perform ABS VERIFICATION TEST.ABS Verification Test

No

- Go To3

3. CHECK THE ABS PUMP MOTOR FUSED B+ FOR AN OPEN
Turn the ignition off.
Remove and visually inspect the ABS Pump Motor B+ fuse.
Is the ABS Pump Motor B+ fuse open?

Yes

- Go To 4

No

- Go To 6

4. CHECK THE (A107) FUSED B(+) FOR A SHORT TO GROUND




Disconnect the Anti-Lock Brake Controller (CAB) harness connector.
Using a 12-volt test light connected to 12-volts, probe the (A107) Fused B+ circuit.
Does the test light illuminate brightly?

Yes

- Repair the (A921) Fused B(+) circuit for a short to ground.
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Go To 5

5. CHECK THE (A107) FUSED B(+) CIRCUIT
Visually inspect the (A107) Fused B(+) circuit in the wiring harness.
Look for any signs of intermittent short to ground.
Is the wiring harness OK?

Yes

- Go To 6

No

- Repair the (A107) Fused B(+) circuit for a short to ground.
- Perform ABS VERIFICATION TEST. ABS Verification Test

6. CHECK THE VOLTAGE ON THE (A107) FUSED B(+) CIRCUIT




Disconnect the Anti-Lock Brake Controller (CAB) harness connector.
Measure the voltage of the (A107) Fused B(+) circuit in the Anti-Lock Brake Controller (CAB) harness connector.
Is the voltage above 10 volts?

Yes

- Go To 7

No

- Repair the (A107) Fused B(+) circuit for an open.
- Perform ABS VERIFICATION TEST. ABS Verification Test

7. CHECK THE (Z903)/(Z933) GROUND CIRCUIT FOR AN OPEN




Measure the resistance of the (Z903)/(Z933) Ground circuit between the Anti-Lock Brake Controller (CAB) harness connector and ground
Is the resistance below 5.0 ohms?

Yes

- Replace the Anti-Lock Brake Controller (CAB).
- Perform ABS VERIFICATION TEST. ABS Verification Test

No

- Repair the high resistance in the affected circuit.
- Perform ABS VERIFICATION TEST. ABS Verification Test