For 1990-2009 cars

### Circuit Description

The DTC P1450 barometric pressure (BARO) sensor circuit diagnostic monitors the operation of the BARO sensor. The BARO sensor and circuitry are located inside of the powertrain control module (PCM). The PCM uses barometric pressure information in order to compensate for altitude changes. The barometric pressure sensor reading is displayed on a scan tool when the ignition switch is ON and the engine is OFF.

### Conditions for Running the DTC

The engine is running.

### Conditions for Setting the DTC

The input range check indicates the following conditions:

The barometric pressure is less than 38 kPa for more than 5 seconds.

OR

The barometric pressure is more than or equal to 113 kPa for more than 5 seconds.

### Action Taken When the DTC Sets

• | The PCM illuminates the malfunction indicator lamp (MIL).

• | The PCM records the operating conditions at the time the diagnostic fails. This information will be stored in the Freeze Frame buffer.

• | The PCM enters the Fail-Safe Function and operates as if the barometric pressure is 101 kPa (760 mm Hg).

### Conditions for Clearing the MIL/DTC

• | The MIL turns OFF after three consecutively passing trips without a fault present.

• | A History DTC clears after 40 consecutive warm-up cycles without a fault.

• | Use the scan tool Clear DTC Information function or disconnect the PCM battery feed in order to clear the DTC.

### Diagnostic Aids

Barometric pressure varies depending on weather conditions and altitude.

If the DTC P1450 is intermittent, driving the vehicle under the following conditions can verify whether the fault is present. Perform the scan tool Clear DTC Information function. Road test the vehicle while monitoring the DTC P1450 diagnostic on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P1450 appears in the Not Ran Since Code Cleared list, the P1450 diagnostic has not yet run. When the DTC P1450 does not appear in the Not Ran Since Code Cleared list, the P1450 diagnostic has run. If the MIL is NOT ILLUMINATED, and there is no PENDING DTC Status in DTC Information, the P1450 diagnostic has passed. DTCs MUST BE CLEARED in order to view the CURRENT STATUS of the Not Ran Since Code Cleared list. DO NOT FORGET that the Not Ran Since Code Cleared list only indicates that the test has run, not whether the test passed or failed. The DTC Information screen must be checked for CURRENT or PENDING status, in order to determine the outcome of the diagnostic test involved.

If DTC P1450 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining vehicle operating conditions when the DTC was first set.

### Test Description

The numbers below refer to the step numbers in the diagnostic table.

1. The Diagnostic System Check-Engine Controls 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. This step determines if a fault is present.

3. This step checks for a short to ground in the PCM 5 volt reference circuit. The BARO sensor shares the 5 volt reference supply from the PCM with the MAP sensor, the TP sensor, and the fuel tank pressure sensor. A short in any branch of the reference voltage circuit will cause a DTC P1450 to set.

Step | Action | Yes | No
--- | --- | --- | ---
1 | Did you perform the Diagnostic System Check-Engine Controls? | Go to Step 2 | Go to Diagnostic System Check - Engine Controls
2 |

1. Turn ON the ignition, leaving the engine OFF.
2. Clear the scan tool information.
3. Operate the vehicle within the Freeze Frame conditions as specified.

Is DTC P1450 set?

Go to Step 3

Go to Diagnostic Aids

3 |

1. Test the 5-volt reference circuit of the following sensors for a short to ground:

• | The manifold absolute pressure (MAP) sensor

• | The throttle position (TP) sensor

• | The fuel tank pressure sensor

2. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Was a repair necessary?

Go to Step 5

Go to Step 4

4 | Replace the PCM. Refer to Powertrain Control Module Replacement . Is the replacement complete? | Go to Step 5 | --
5 |

1. Use the scan tool in order to clear the DTCs.
2. Turn OFF the ignition for 30 seconds.
3. Start the engine.
4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

Go to Step 6

Go to Step 2

6 | With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? | Go to Diagnostic Trouble Code (DTC) List | System OK