P258B Electronic Vacuum Pump Performance

P258B Electronic Vacuum Pump Performance - The Electric Vacuum Pump (EVP) system is installed to provide supplemental vacuum to the brake booster, when the engine vacuum supply is low. The pumps is connected to the engine and the brake booster through a series of hoses and one-way flow check valves. A pressure sensor, mounted in the brake booster, provides information to the ABS/ESP Module. This information is then sent to the Powertrain Control Module (PCM) over the CAN C BUS. 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 engine running, the PCM monitors the change in vacuum in the brake booster when the EVP is commanded on over a calibrated threshold of time. Set condition the PCM detects that the chenge in vacuum during the testing period is less than a calibrated threshold. Default action MIL light will illuminate.

Possible causes P258B Code

  • Fused B+ circuit open.
  • Electric Vacuum Pump output circuit open/high resistance.
  • Electric Vacuum Pump output circuit shorted to ground.
  • Ground circuit open/high resistance.
  • Pinched, cut or open vacuum supply line.
  • Vacuum pressure sensor.
  • Brake booster.
  • Electric Vacuum Pump.
  • Antilock Brake System (ABS) Module.

Diagnose DTC P258B Code

Step 1. Check for an active DTC
If DTC P258A is active, perform the diagnostic procedure for P258A before continuing with this test. Diagnose and repair any vacuum pressure sensor DTC that are present in the PCM or ABS Module before continuing with this test procedure. Start the engine and allow it to idle. Press and release the Brake pedal several times to cause the EVP to operate. With the scan tool, read DTC.

Is the DTC active or pending?

Yes, go to step 2.
No, perform the the PCM intermittent condition.

Step 2. Electric Vacuum Pump actuation
Turn the ignition on, engine not running. With the scan tool actuate the Electronic Vacuum Pump.

Does the Electronic Vacuum Pump run?

Yes, go to step 8.
No, go to step 3.

Step 3. Check the Electronic Vacuum Pump output circuit
Disconnect the EVP harness connector. With the scan tool actuate the Electronic Vacuum Pump. Using a 12-volt test light connected to ground, probe the Electric Vacuum Pump output circuit at the Electronic Vacuum Pump harness connector.

Does the test light illuminate brightly?

Yes, go to step 4.
No, go to step 5.

Step 4. Check the EVP ground circuit
Check a 12-volt test light connected to 12-volts, probe the EVP ground circuit at the Electric Vacuum Pump harness connector.

Does the test light illuminate brightly?

Yes, replace the Electric Vacuum Pump.
No, repair the EVP ground circuit for an open.

Step 5. Check the Electric Vacuum Pump output circuit for an open/high resistance
Turn the ignition off, remove the EVP relay from the relay connector. Measure the resistance of the Electric Vacuum Pump output circuit between the EVP relay connector and the EVP harness connector.

Is the resistance below 3.0 Ohms?

Yes, go to step 6.
No, repair the Electric Vacuum Pump output circuit for an open or high resistance.

Step 6. Check the Electric Vacuum Pump output circuit for a short to ground
Check for continuity between ground and the Electric Vacuum Pump output circuit at the EVP relay connector.

Is there continuity between ground and the Electric Vacuum Pump output circuit?

Yes, repair the Electric Vacuum Pump output circuit for a short to ground. If the circuit was shorted to ground, test the fuse in the fuse box and replace as necessary.

No, go to step 7.

Step 7. Check the Fused B+ circuit at the EVP relay
Turn the ignition on, using a 12-volt test light connected to ground, probe the Fused B+ circuit at the EVP relay connector (terminal 30).

Does the test light illuminate brightly?

Yes, replace the Vacuum Pump relay. With the scan tool actuate the Electronic Vacuum Pump. Using a 12-volt test light connected to ground, probe the Electric Vacuum Pump output circuit at the Electric Vacuum Pump harness connector. If the test light still does not illuminate brightly, replace the Front PDC/Fused Box.

No, repair the Fused B+ circuit for an open or short to ground. If no problems are found with the Fused B+ circuit and the fuse is not blown, replace the TIPM or BCM.

Step 8. Check the Vacuum supply line
Turn the ignition off. Check the vacuum supply line to brake booster for a pinched, cut or open hose.

Were any problems found?

Yes, repair as necessary.
No, go to step 9.

Step 9. Vacuum Pressure signal
Start the engine. With the scan tool, view and record the vacuum pressure signal with foot off the brake pedal. With the scan tool, view the vacuum pressure signal while pressing the brake pedal several times. Record the highest value.

Without the brake pedal applied, was the vacuum presure signal -40 kpa (-12 in hg)?

Yes, go to step 10.
No, replace the Brake booster.

Step 10. Check for vacuum pressure signal change
Turn the ignition on, remove the Vacuum Pressure sensor from the Brake booster. Connect a vacuum pump to the vacuum pressure sensor. 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 step 11.
No, replace the Vacuum Pressure Sensor.

Step 11. Check brake booster check valve
Remove the Brake booster check valve. Apply vacuum to the booster side of the check valve.

Is the Brake booster check valve holding vacuum?

Yes, go to step 12.
No, replace the Brake Booster check valve.

Step 12. Check Brake Booster

Reinstall the Brake Booster check valve. Apply vacuum to the brake booster.

Is the Brake booster holding vacuum?

Yes, go to step 13.
No, replace the Brake booster.

Step 13. Check related PCM and component connections

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