2010 Cadillac CTS Sedan AWD V6-3.6L Page 1220
4. Verify that a test lamp does not illuminate between the control circuit terminal 85 and ground.
瀚慖f the test lamp illuminates, test the control circuit for a short to voltage.
5. Disconnect the harness connector at the vacuum pump.
6. Test for less than 2 ohms between the vacuum pump ground circuit terminal 2 and ground.
瀚慖f greater than the specified range, test the ground circuit for an open/high resistance.
7. Connect the harness connector at the vacuum pump.
8. Connect a 20A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87. Verify the vacuum pump is
activated.
瀚慖f the vacuum pump does not activate, test the control circuit for a short ground or an open/high resistance. If the circuit tests normal, test
or replace the vacuum pump.
9. Ignition OFF, test for infinite resistance between the control circuit terminal 85 and ground.
瀚慖f less than the specified value, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM.
10. Disconnect the X1 harness connector at the ECM.
11. Test for less than 2 ohms between the control circuit terminal 85 at the relay cavity and terminal 18 at the ECM harness connector.
瀚慖f greater than the specified range, test the control circuit for an open/high resistance.
12. If all circuits test normal, replace the brake booster pump relay. If the DTC resets, replace the power brake booster vacuum pump.
Component Testing
1. Ignition OFF, disconnect the vacuum pump relay.
2. Test for 60-180 ohms between terminals 85 and 86.
瀚慖f the resistance is not within the specified range, replace the relay.
3. Test for infinite resistance between the following terminals:
* 30 and 85
* 30 and 87
* 30 and 86
* 86 and 87
瀚慖f not the specified value, replace the relay.
4. Install a 30A fused jumper wire between relay terminal 86 and B+. Install a jumper wire between relay terminal 85 and ground.
5. Test for less than 2 ohms between terminals 30 and 87.
瀚慖f greater than the specified range, replace the 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))
* Power Brake Booster Auxiliary Pump Replacement (See: Brakes and Traction Control/Power Brake Assist/Hydraulic Brake Booster
Pump/Service and Repair)
* Control Module References (See: Testing and Inspection/Programming and Relearning) for ECM replacement, setup, and programming
P258C
DTC P258A-P258D
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.
