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DTC P1128: MAP Sensor Signal Lower Than Expected

NOTE:
  • Before you troubleshoot, record all freeze data and any on-board snapshot, and review the general troubleshooting information (see GENERAL TROUBLESHOOTING INFORMATION ).
  • Before starting this troubleshooting check for poor connections or a blockage at the intake air duct.
  1. Turn the ignition switch to ON (II).
  2. Check the MAP SENSOR in the DATA LIST with the HDS.

    Is less than 54.1 kPa (16.0 in.Hg, 406 mmHg), or 1.61 V held for more than 5 seconds? 

    YES  -Go to step  7.

    NO  -Go to step 3.

  3. Clear the DTC with the HDS.
  4. Start the engine. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
  5. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)
    • ENGINE SPEED between 1, 200-5, 500 rpm
    • Transmission in D
    • Vehicle speed accelerated from 16-31 mph (25-50 km/h) under half throttle
  6. Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.

    Does the HDS indicate FAILED? 

    YES  -Go to step 7.

    NO  -If the HDS indicates PASSED, intermittent failure, the system is OK at this time. Check for poor connections or loose terminals at the MAP sensor and the PCM. If the HDS indicates NOT COMPLETED, Go to step  4 and recheck.

  7. Turn the ignition switch to LOCK (0).
  8. Replace the MAP sensor (see MAF SENSOR/IAT SENSOR REPLACEMENT ).
  9. Turn the ignition switch to ON (II).
  10. Reset the PCM with the HDS.
  11. Do the PCM idle learn procedure (see PCM IDLE LEARN PROCEDURE ).
  12. Start the engine. Hold the engine speed at 3, 000 rpm without load (in P or N) until the radiator fan comes on, then let it idle.
  13. Test-drive under these conditions:
    • Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)
    • ENGINE SPEED between 1, 200-5, 500 rpm
    • Transmission in D
    • Vehicle speed accelerated from 16-31 mph (25-50 km/h) under half throttle
  14. Check for Pending DTCs or Confirmed DTCs with the HDS.

    Is DTC P1128 indicated? 

    YES  -Check for poor connections or loose terminals at the MAP sensor and the PCM, then Go to step  1.

    NO  -Go to step 15.

  15. Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.

    Does the HDS indicate PASSED? 

    YES  -Troubleshooting is complete. If any other Pending DTCs or Confirmed DTCs were indicated in step 14, Go to the indicated DTC's troubleshooting. ■

    NO  -If the HDS indicates FAILED, check for poor connections or loose terminals at the MAP sensor and the PCM, then Go to step  1. If the HDS indicates NOT COMPLETED, Go to step  12.

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