DTC Troubleshooting

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.

1. Inspect the air cleaner element.

Is there damage or clogging?

YES - Replace the air cleaner element. Then clear the DTC with the HDS, and Go to step 13.

NO - Go to step 2.

2. Turn the ignition switch ON (II).
3. Check the MAP SENSOR in the DATA LIST with the HDS.

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

YES - Go to step 8.

NO - Go to step 4.

4. Clear the DTC with the HDS.
5. 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.
6. Test-drive under these conditions:
- ECT SENSOR 1 above 158 °F (70 °C)
- Engine speed between 1,400 and 6,500 rpm
- Transmission in 3rd gear
- Vehicle speed at 15 mph (24 km/h) or more, and engine speed between 1,300 rpm and 7,600 rpm for 2 seconds or more.

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

Does the screen indicate FAILED?

YES - Go to step 8.

NO - If the screen 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 screen indicates NOT COMPLETED, Go to step 5 and recheck.

8. Turn the ignition switch OFF.
9. Replace the MAP sensor.
10. Turn the ignition switch ON (II).
11. Reset the ECM with the HDS.
12. Do the ECM idle learn procedure.
13. 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.
14. Test-drive under these conditions:
- ECT SENSOR 1 above 158 °F (70 °C)
- Engine speed between 1,400 and 6,500 rpm
- Transmission in 3rd gear
- Vehicle speed at 15 mph (24 km/h) or more, and engine speed between 1,300 rpm and 7,600 rpm for 2 seconds or more.

15. Check for Temporary DTCs or DTCs with the HDS.

Is DTC P1128 indicated?

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

NO - Go to step 16.

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

Does the screen indicate PASSED?

YES - Troubleshooting is complete. If any other Temporary DTCs or DTCs were indicated in step 15, Go to the indicated DTCs troubleshooting.

NO - If the screen indicates FAILED, check for poor connections or loose terminals at the MAP sensor and the ECM, then Go to step 1. If the screen indicates NOT COMPLETED, Go to step 14.