2010 Cadillac CTS Sedan AWD V6-3.6L Page 652
瀚慖f the brake booster pump does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace
the brake booster pump.
9. Connect a test lamp between the ignition circuit terminal 86 and the control circuit terminal 85.
10. Command the brake booster pump ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the
commanded states.
瀚慖f the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the brake booster pump.
瀚慖f the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace
the brake booster pump.
11. If all circuits test normal, test or replace the brake booster pump relay.
Component Testing
Vacuum Pump Motor Test
1. Ignition OFF, disconnect the harness connector at the M9 brake booster pump.
2. Connect a 20 A fused jumper wire between the control circuit terminal 1 and B+.
3. Connect a jumper wire between the ground circuit terminal 2 and ground, verify the M9 brake booster pump activates.
瀚慖f the M9 brake booster pump does not activate, replace the M9 brake booster pump motor.
Relay Test
1. Ignition OFF, disconnect the brake booster pump relay.
2. Test for 60-100 ohm between terminals 85 and 86 of the relay.
瀚慖f not within the specified range, replace the brake booster pump relay.
3. Test for infinite resistance between the following terminals:
* 30 and 85
* 30 and 86
* 30 and 87
瀚慖f less than the specified value, replace the brake booster pump relay.
4. Install a fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground.
5. Test for less than 5 ohm between terminals 30 and 87.
瀚慖f greater than the specified value, replace the brake booster pump relay.
Repair Instructions
Perform the Diagnostic Repair Verification (See: Verification Tests) after completing the diagnostic procedure.
* Relay Replacement (Attached to Wire Harness) (See: Power and Ground Distribution/Power Distribution Relay/Service and Repair/Relay
Replacement (Attached to Wire Harness))Relay Replacement (Within an Electrical Center) (See: Power and Ground Distribution/Power
Distribution Relay/Service and Repair/Relay Replacement (Within an Electrical Center))
* Control Module References (See: Testing and Inspection/Programming and Relearning) for EBCM replacement, setup, and programming
C028A
DTC C028A
Diagnostic Instructions
* Perform the Diagnostic System Check - Vehicle (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic System
Check - Vehicle) prior to using this diagnostic procedure.
* Review Strategy Based Diagnosis (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Strategy Based Diagnosis) for an
overview of the diagnostic approach.
* Diagnostic Procedure Instructions (See: Testing and Inspection/Initial Inspection and Diagnostic Overview/Diagnostic Procedure
Instructions) provide an overview of each diagnostic category.
DTC Descriptors
DTC C028A 01
- Park Brake Motor Circuit Short to Battery
