Circuit Description
The electronic brake control module (EBCM) monitors the HydroMax assist relay and the HydroMax motor for electrical continuity.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC C0272 Base Brake Pump Motor Circuit
Conditions for Running the DTC
The ignition is ON.
Conditions for Setting the DTC
| • | The EBCM detects open Hydromax assist relay contacts while the relay is energized. |
| • | The EBCM detects an open Hydromax pump motor or pump motor circuit. |
Action Taken When the DTC Sets
| • | The service brake soon indicator turns ON. |
| • | A fast rate audible chime turns ON. |
Conditions for Clearing the DTC
The conditions for setting the DTC are no longer present.
Diagnostic Aids
| • | Inspect the 10 A Hydromax fuse for an open. |
| • | Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. Refer to Testing for Electrical Intermittents , Testing for Intermittent Conditions and Poor Connections , Wiring Repairs and Connector Repairs in Wiring Systems. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
Listen for an audible click when the brake pedal is pressed and released.
-
This step tests whether or not the EBCM is able to energize the hydromax relay.
-
This step tests for voltage supplied to the hydromax pump motor when the hydromax relay is energized.
Step | Action | Yes | No |
|---|---|---|---|
Schematic Reference: Brake Warning System Schematics and Power Brake Booster Pump Schematics Connector End View Reference: Hydraulic Brake Connector End Views | |||
1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Does the DTC set? | Go to Step 3 | Go to Diagnostic Aids |
3 | Press the brake pedal. Does the hydromax pump motor run when the brake is applied? | Go to Step 14 | Go to Step 4 |
press and release the brake pedal several times. Does the hydromax relay click each time the brake pedal is pressed and released? | Go to Step 7 | Go to Step 5 | |
Does the test lamp illuminate when the brake pedal is pressed? | Go to Step 12 | Go to Step 6 | |
6 |
Did you find and correct the condition? | Go to Step 17 | Go to Step 15 |
Does the test lamp illuminate when the brake pedal is pressed? | Go to Step 10 | Go to Step 8 | |
8 | Test the battery positive voltage circuit to the hydromax relay for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 9 |
9 | Test the brake booster pump motor supply voltage circuit and the hydromax pump motor ground circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 12 |
10 | Inspect for poor connections at the harness connector of the hydromax pump motor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 11 |
11 | Replace the hydromax pump motor. Refer to Power Brake Booster Pump Replacement. Did you complete the replacement? | Go to Step 17 | -- |
12 | Inspect for poor connections at the harness connector of the hydromax relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 13 |
13 | Replace the hydromax relay. Did you complete the replacement? | Go to Step 17 | -- |
14 | Turn the ignition off and test the hydromax motor feedback circuit for an open between terminal 10 of the EBCM connector and terminal A of the pump motor connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 15 |
15 | Inspect for poor connections at the harness connector of the EBCM. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 |
16 | Replace the EBCM. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | -- |
17 |
Does the DTC reset? | Go to Step 3 | System OK |
