P258B

P258B-ELECTRIC VACUUM PUMP PERFORMANCE





For a complete wiring diagram, refer to the Wiring Information .

Theory of Operation

The Electric Vacuum Pump (EVP) system is installed to provide supplemental vacuum to the brake booster, when the engine vacuum supply is low. The pump is connected to the engine and the brake booster through a series of hoses and one-way flow check valves. A pressure senor, mounted in the brake booster, provides information to the ABS/ESP module, the vacuum level is then sent over CAN to the Powertrain Control Module (PCM). The PCM modulates the EVP operation to maintain the brake booster vacuum within a given range. This system ensures that the customer experiences a consistent brake pedal feel under all driving conditions.

- When Monitored:
With the ignition on and engine running.

- Set Condition:
Minimum Manifold Absolute Pressure (MAP) reading is 15 kpa (4.4 inHg). EVP minimum vacuum is -35 kpa (-10 inHg) and the EVP cannot create 3 kpa (1 inHg) or the system cannot increase the vacuum from -35 kpa (-10 inHg) to -38 kpa (-11 inHg). Two trip fault. Three good trips to turn off the MIL.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC

NOTE: Diagnose and repair any communication or low voltage DTCs before proceeding with this test.

1. Ignition on, engine not running.
2. With the scan tool, select View DTCs.

Is the DTC Active or Pending at this time?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

2. ENGINE WITH ELECTRIC VACUUM PUMP
1. Verify vehicle is equipped with an electric vacuum pump.

Is the vehicle is equipped with an electric vacuum pump?

Yes

- Go To 3

No

- Go To 9

3. CHECK FOR PINCHED VACUUM SUPPLY LINE
1. Turn the ignition off.
2. Check the vacuum supply line to brake booster for a pinched, cut or open hose.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 4

4. VACUUM PRESSURE SIGNAL
1. Start the engine.
2. With the scan tool, view and record the vacuum pressure signal with foot off the brake pedal.
3. With the scan tool, view the vacuum pressure signal while pressing the brake pedal several times.
4. Record the highest value.

Without the brake pedal applied, was the vacuum pressure signal -40 kpa (-12 inHg)?

Yes

- Go To 5

No

- Replace the Power Brake Booster. Power Brake Booster - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. CHECK FOR VACUUM PRESSURE SIGNAL CHANGE
1. Turn the ignition on.
2. Remove the Vacuum Pressure Sensor from the Booster.
3. Connect a vacuum pump to the Vacuum Pressure Sensor.
4. Apply vacuum to the Vacuum Pressure Sensor and watch for signal change.

Is the voltage signal changing on the scan tool as vacuum is being applied?

Yes

- Go To 6

No

- Replace the Power Brake Booster. Power Brake Booster - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. CHECK BRAKE BOOSTER CHECK VALVE
1. Remove the Brake Booster Check Valve.
2. Apply vacuum to the booster side of the check valve.

Is the Brake Booster Check Valve holding vacuum?

Yes

- Go To 7

No

- Replace the Power Brake Booster. Power Brake Booster - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

7. CHECK BRAKE BOOSTER
1. Reinstall the Brake Booster Check Valve.
2. Apply vacuum to the Brake Booster.

Is the Brake Booster holding vacuum?

Yes

- Go To 8

No

- Replace the Power Brake Booster. Power Brake Booster - Removal.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. ELECTRIC VACUUM PUMP
1. Turn the ignition on.
2. With the scan tool actuate the Electronic Vacuum Pump.

Did the Electric Vacuum Pump run?

Yes

- Go To 9

No

- Perform the diagnostic procedure for P258A. P258A.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

9. ANTI-LOCK BRAKE SYSTEM (ABS)
1. Turn the ignition off to the lock position.
2. Perform any Technical Service Bulletins that may apply.
3. Inspect the related wiring harness. Look for any chafed, pierced, pinched or partially broken wires.
4. Inspect the related wire harness connectors. Look for broken, bent, pushed out or corroded terminals.

Were any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace the Anti-lock Brake System (ABS) Module. Anti-Lock Brake System Module - Removal.
- Perform the ABS VERIFICATION TEST. ABS Verification Test.