DTC P1129: MAP Sensor Signal Higher Than Expected

NOTE: Before you troubleshoot, record all freeze data and any on-board snapshot, and review GENERAL TROUBLESHOOTING INFORMATION .

Check for vacuum leaks in these parts:
- PCV valve
- PCV hose
- EVAP canister purge valve
- Throttle body
- Intake manifold
- Brake booster
- Brake booster hose
  Are there any vacuum leaks?
  
  YES: Repair or replace the parts with vacuum leaks, then go to step 9.
  
  NO: Go to step 2.
Start the engine. Hold the engine speed at 3.000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
Check the MAP SENSOR in the DATA LIST with the HDS.
Is more than 36.9 kPa (11.0 in.Hg, 277 mmHg), or 1.1 V held for more than for 5 seconds?

YES: Go to step 7.

NO: Go to step 4.
Clear the DTC with the HDS.
Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)
- A/T in D, M/T in 5th
- Drive at a steady speed between 55-75 mph (88-120 km/h) for 10 seconds
- During the drive, decelerate (with the throttle fully closed) for at least 2 seconds
Monitor the OBD STATUS for DTC P1129 in the DTCs MENU with the HDS.
Does the screen 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 ECM/PCM. If the HDS indicates NOT COMPLETED, go to step 5 and recheck.
Turn the ignition switch to LOCK (0).
Replace the MAP sensor (see MAF SENSOR/IAT SENSOR REPLACEMENT ).
Turn the ignition switch to ON (II).
Reset the ECM/PCM with the HDS.
Do ECM/PCM IDLE LEARN PROCEDURE .
Start the engine. Hold the engine speed at 3, 000 rpm without load (A/T in P or N, M/T in neutral) until the radiator fan comes on, then let it idle.
Test-drive under these conditions:
- Engine coolant temperature (ECT SENSOR 1) above 158°F (70°C)
- A/T in D, M/T in 5th
- Drive at a steady speed between 55-75 mph (88-120 km/h) for 10 seconds
- During the drive, decelerate (with the throttle fully closed) for at least 2 seconds
Check for Pending or Confirmed DTCs with the HDS.
Is DTC P1129 indicated?

YES: Check for poor connections or loose terminals at the MAP sensor and the ECM/PCM, then go to step 1.

NO: Go to step 15.
Monitor the OBD STATUS for DTC P1129 in the DTCs MENU with the HDS.
Does the screen indicate PASSED?

YES: Troubleshooting is complete. If any other Pending 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 ECM/PCM, then go to step 1. If the HDS indicates NOT COMPLETED, go to step 12.