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For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2001 🢒 Tracker - 2WD 🢒 Engine 🢒 Engine Controls - 2.5L (LE8) 🢒 DTC P1451

Description

The DTC P1451 Barometric Pressure (BARO) Sensor Performance diagnostic checks the accuracy of the BARO sensor signal. The BARO sensor and circuitry are located inside of the powertrain control module (PCM). The PCM uses the barometric pressure information in order to compensate for changes in altitude and weather conditions.

Condition for Running the DTC

The engine is running in Closed Loop.

Conditions for Setting the DTC
    • The engine is operating in the Fuel Cut-off mode.
    • The difference between the observed barometric pressure reading and the manifold absolute pressure (MAP) sensor reading is not within a specified value.
    • The above conditions are met for 5 seconds or more.

Action Taken When the DTC Sets
    • The PCM illuminates the malfunction indicator lamp (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
    • The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Freeze Frame buffer.

Conditions for Clearing the MIL/DTC
    • The MIL turns OFF after 3 consecutively passing trips without a fault present.
    • A history DTC clears after 40 consecutive warm-up cycles without a fault.
    • Perform the scan tool Clear DTC Information function.

Diagnostic Aids

A malfunctioning or skewed MAP sensor may cause DTC P1451 to set.

The barometric pressure varies depending on the weather conditions and the altitude. Typical barometric pressure at sea level is 100 kPa (29-30 in Hg).

If a DTC P1451 cannot be duplicated, the information included in the Freeze Frame data can be useful in determining the 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.

  2. This step checks for a MAP sensor fault.

    3.

  3. This step checks the accuracy of the MAP sensor. The MAP sensor should indicate atmospheric pressure when the ignition is ON and the engine is not running.

    4.

  4. This step checks for a faulty BARO sensor. The BARO sensor and the MAP sensor should indicate approximately the same pressure when the ignition is ON and the engine is not running.

    5.

  5. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P1451 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P1451 appears in the Not Ran Since Code Cleared list, the DTC P1451 diagnostic has not yet run. When the DTC P1451 does not appear in the Not Ran Since Code Cleared list, the DTC P1451 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P1451 diagnostic has passed. The 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.

    6.

  6. Clearing the DTCs by removing the DOME fuse also clears the PCM long term memory. Using the scan tool to clear DTCs leaves the long term memory active. DTC emitting diagnostics may not run to completion as expected unless the long term memory is cleared. Removal of the DOME fuse also clears the time display of the radio. The DTC P1451 diagnostic can be monitored on the scan tool under the Not Ran Since Code Cleared selection in the DTC Information menu. If a DTC P1451 appears in the Not Ran Since Code Cleared list, the DTC P1451 diagnostic has not yet run. When the DTC P1451 does not appear in the Not Ran Since Code Cleared list, the DTC P1451 diagnostic has run. If the MIL is NOT illuminated, and there is no Pending DTC Status in DTC Information, the DTC P1451 diagnostic has passed. The 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.

Step

Action

Value(s)

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Check for DTC P1408.

Is DTC P1408 set?

--

Go to DTC P1408

Go to Step 3

3
  1. Turn ON the ignition, leaving the engine OFF.
  2. Clear the scan tool information.
  3. Select the MAP sensor parameter on the scan tool.

Is the MAP sensor pressure reading near the specified value?

97-100 kPa at sea level

Go to Step 4

Go to Step 7

4
  1. Turn ON the ignition, leaving the engine OFF.
  2. Compare the pressure readings of the BARO sensor and the MAP sensor on the scan tool.

Is the difference between the BARO pressure and the MAP pressure more than the specified value?

3 kPa

Go to Step 8

Go to Step 5

5
  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 or until the DTC P1451 diagnostic test has run. Refer to the Test Description.

Is a DTC P1451 set?

--

Go to Step 6

Go to Diagnostic Aids

6
  1. Select the Freeze Frame/Failure Record for the current DTC P1451 on the scan tool.
  2. Review the MAP sensor readings in the Freeze Frame/Failure Record.

Were the recorded MAP sensor readings normal?

--

Go to Step 8

Go to Step 7

7
  1. Inspect the MAP sensor for the following conditions:
    2. • A skewed or incorrectly calibrated MAP sensor
    • A blockage or restriction in the MAP sensor vacuum supply
    • Electrical resistance in the MAP sensor signal circuit
  2. Repair as necessary.

Did you complete the action?

--

Go to Step 9

--

8

Replace the PCM. Refer to Powertrain Control Module Replacement .

Is the action complete?

--

Go to Step 9

--

9
  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 or until the DTC P1451 diagnostic test has run. Refer to the Test Description.

Does the DTC run and pass?

--

Go to Step 10

Go to Step 2

10

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