P1451

Diagnostic Chart:

Circuit Description

The Barometric Pressure Sensor reading is displayed from the Powertrain Control Module (PCM) at ignition switch on, engine off and at wide open throttle. The Barometric Pressure Sensor represents barometric pressure and is used to compensate for altitude changes.


Conditions for Setting the DTC

Comparison with the MAP sensor:

- Difference between barometric pressure and manifold absolute pressure is 67 kPa or more.

- CTP switch ON.

- Engine speed greater than 2000 RPM.

- The above conditions are met for 5 seconds or more.


Action Taken When the DTC Sets

- The Malfunction Indicator Lamp (MIL) will illuminate after two consecutive ignition cycles in which the diagnostic runs with the fault active.

- The PCM will record operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.


Conditions for Clearing the MIL/DTC

- The MIL will turn off after three consecutive drive cycles without a fault present.

- A DTC will clear after 40 consecutive warm-up cycles without a fault.

- The DTCs can be cleared by using a scan tool or by disconnecting the PCM battery feed.


Diagnostic Aids


Check for the following conditions:

- A faulty MAP sensor input to the PCM can cause a DTC P1451 to set. Check for a good vacuum supply to the MAP sensor. Also check for a poor electrical connection in the MAP sensor circuit or a faulty MAP sensor.

- A poor connection at the PCM. Inspect the harness connectors for backed out terminal, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal to wire connection.

- A damaged wiring harness. Inspect the wiring harness for damage and repair as necessary.

- Note that barometric pressure varies depending on weather conditions as well as altitude.

If a DTC P1451 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was last set. This may assist in determining how often the DTC sets.

If any wiring repairs need to be made, Refer to Repair Procedures in Diagrams/Electrical.


Test Description

The numbers below refer to the step numbers in the Diagnostic Table.

1. The Powertrain (OBD) System Check prompts the technician to complete some basic checks and store the Freeze Frame data on the scan tool if applicable. This creates an electronic copy of the data taken when the fault occurred. The information is then stored in the scan tool for later reference.

2. Determine if a fault is present. Review the Freeze Frame data to determine when the DTC set. Always record this information.