For 1990-2009 cars only
Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptor
DTC C0272: Base Brake Pump Motor CircuitDiagnostic Fault Information
Circuit | Short to Ground | Open/High Resistance | Short to Voltage | Signal Performance |
|---|---|---|---|---|
Power Brake Booster Pump Relay Coil Ground (terminal 86) | -- | 1 | -- | -- |
Power Brake Booster Pump Relay Switch Ground (terminal 30) | 1 | 1 | -- | -- |
Power Brake Booster Pump Relay Coil control (terminal 85) | -- | 2 | -- | |
Relay Controlled Output (terminal 87) | 1 | 1 | -- | -- |
Brake booster pump motor signal | 1 | C0272 | -- | -- |
Brake booster fluid flow switch signal | 1 | C0272 | -- | -- |
1. Power Brake Booster Pump Relay Malfunction 2. Power Brake Booster Pump Relay Coil Control Malfunction | ||||
Circuit/System Description
The electronic brake control module (EBCM) monitors the HydroMax assist relay and HydroMax motor for electrical continuity.
Conditions for Running the DTC
Ignition ON.
Conditions for Setting the DTC
| • | The EBCM detects an open HydroMax assist relay contacts while the relay is energized. |
| • | The EBCM detects an open HydroMax (brake booster pump fluid flow switch signal) or (brake booster pump motor signal). |
Action Taken When the DTC Sets
| • | The service brake soon indicator illuminates. |
| • | 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 10A HydroMax fuse (JE3) on the EBCM brake booster pump motor signal circuit for an open. |
| • | Thoroughly inspect connections or circuitry that may cause an intermittent malfunction. |
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Brake Warning System Description and Operation
Electrical Information Reference
| • | Circuit Testing |
| • | Wiring Repairs |
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
Press and release the brake pedal several times, each time the power brake booster pump relay should click.
Circuit/System Testing
- Ignition OFF, disconnect the power brake booster pump relay.
- Test for less than 1.0 ohm between the relay coil ground circuit terminal 86 and ground.
- Test for less than 1.0 ohm between the relay switch ground circuit terminal 30 and ground.
- Ignition OFF, disconnect the brake booster pump harness connector at the EBCM.
- Verify that a test lamp illuminates between the power brake booster relay switch B+ circuit terminal 87 and ground.
- Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 30 and B+.
- Connect the power brake booster pump relay harness connector at the EBCM.
- Connect a 3A fused jumper wire between the relay ground circuit terminal 87 and the control circuit terminal 30. Verify the power brake booster pump motor is activated.
- Connect a test lamp between the relay coil control circuit terminal 85 and the relay coil ground circuit terminal 86.
- Press the brake pedal several times. The test lamp should turn ON and OFF when changing between the brake pedals pressed and depressed states.
- Ignition OFF. Disconnect the EBCM harness at the power brake booster pump relay. Connect a test light between the EBCM brake booster pump motor signal terminal 10 and EBCM brake booster fluid flow switch signal terminal 28.
- Press the brake pedal several times. The test lamp should turn ON and OFF when changing between the brake pedals pressed and depressed states.
- If all circuits test normal, test or replace the power brake booster pump relay.
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance |
| ⇒ | If greater than the specified range, test the ground circuit for an open/high resistance. |
| ⇒ | If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse 4 60A is open, test or replace the power brake booster pump motor. |
| ⇒ | If the test lamp illuminates, test the control circuit for a short to ground. |
| ⇒ | If it does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the power brake booster pump motor. |
| ⇒ | If the test lamp is always ON, test the control circuit for a short to voltage. If the circuit tests normal, replace the EBCM. |
| ⇒ | If the test lamp is always OFF, test the control circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the EBCM |
| ⇒ | If the test lamp is always OFF, test the brake switch signal circuit and the brake booster fluid flow switch signal circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the relay. |
Component Testing
Relay Test
- Ignition OFF, disconnect the power brake booster pump relay.
- Test for 1-5 ohms between terminals 85 and 86.
- Test for infinite resistance between the following terminals:
- Install a 3A fused jumper wire between relay terminal 85 and 12 volts. Install a jumper wire between relay terminal 86 and ground. Test for less than 2.0 ohms between terminals 30 and 87.
| ⇒ | If the resistance is not within the specified range, replace the relay. |
| • | 30 and 86 |
| • | 30 and 87 |
| • | 30 and 85 |
| • | 85 and 87 |
| ⇒ | If not the specified value, replace the relay. |
| ⇒ | If greater than the specified range, replace the relay. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
| • | Control Module References for EBCM replacement, setup, and programming |
