DTC Troubleshooting

Control System DTCs

DTC Troubleshooting: P1128

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 How To Troubleshoot The Fuel And Emissions Systems.
* Before you begin, check for poor connections or a blockage at the intake air duct.

1. MAP sensor performance check:

MAP sensor performance check
-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 inHg, 406 mmHg) or 1.61 V held for more than 5 seconds?
-YES- Replace the MAP sensor Service and Repair, then do the repair verification.
-NO- Go to step 2.

2. Problem verification:

Problem verification
-1. Clear the DTC with the HDS.

-2. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) until the radiator fan comes on, then let it idle.

-3. Test-drive under these conditions:
* Engine coolant temperature (ECT SENSOR 1) above 158 °F (70 °C)
* Engine speed at 1,400 rpm or more
* Transmission in 3rd
* Vehicle speed accelerated to 15 mph (24 km/h) or more under half throttle

-4. Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.

Does the HDS indicate FAILED?
-YES- The failure is duplicated. Replace the MAP sensor Service and Repair, then do the repair verification.
-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. If the HDS indicates NOT COMPLETED, go to step 2-2 and recheck.

Repair verification (OBD STATUS check):

-1. Turn the ignition switch to ON (II).

-2. Reset the ECM with the HDS How To Troubleshoot The Fuel And Emissions Systems.

-3. Do the ECM idle learn procedure ECM/PCM Idle Learn Procedure.

-4. Start the engine. Hold the engine speed at 3,000 rpm without load (in neutral) 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 at 1,400 rpm or more
* Transmission in 3rd
* Vehicle speed accelerated to 15 mph (24 km/h) or more under half throttle

-6. Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.

Does the HDS indicate PASSED, FAILED, or NOT COMPLETED?
-PASSED- Troubleshooting is complete. If any other Pending or Confirmed DTCs were indicated, go to the indicated DTC's troubleshooting.
-FAILED- Go to step 1 and recheck.
-NOT COMPLETED- Meet the test condition, and check the OBD STATUS again.