P1251 Code failures by brands


Description of DTC code P1251

Some engines have a vacuum reservoir. This is installed in the passenger side breather area under the breather cover or grille panel. It is necessary to remove the cowl cover to access the reservoir when servicing, but the damaged reservoir cannot be repaired and must be replaced.

The engine vacuum is stored in the reservoir and is used to operate the vehicle accessories controlled by the reservoir during periods of low engine vacuum. For example, in steep uphill driving conditions or under other conditions that require a high engine load.

An on/off solenoid is provided for the vacuum reservoir and is constantly monitored to verify the proper performance. The DTC P1251 OBDII code is set by the ECM when a short to ground is detected in the circuit controlling this vacuum reservoir solenoid.

Symptoms of fault code P1251

  • Check Engine light ON.
  • Decreased engine power at low engine speeds.

Causes of OBD2 P1251

The P1251 OBD2 fault code is stored for one of the following reasons:

  • The vacuum reservoir solenoid harness may be damaged.
  • The vacuum reservoir solenoid circuit connections may be faulty.
  • The vacuum reservoir solenoid may be defective.

Possible solutions of the DTC code P1251

Steps to troubleshoot the P1251 OBDII diagnostic code:

  • Consult the Technical Service Bulletins.
  • Check all the wiring related to the vacuum reservoir solenoid and check for common damage. If wear or burns are discovered, make repairs.
  • Verify that the solenoid circuit connections are not faulty enough to cause a short or open circuit. If such conditions are found, make corrections.
  • Measure the vacuum reservoir solenoid resistance and verify that the vacuum reservoir solenoid resistance is correct. Compare this result with the manufacturer's specifications. If you detect an out-of-range resistance, replace the solenoid.

Codes related to P1251

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