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.
Before you begin, check for poor connections or a blockage at the intake air duct.

DTC Description
Confirmed DTC
Pending DTC
Freeze Frame
P1128 MAP Sensor Signal Lower Than Expected
      

1.
MAP sensor performance check:

MAP sensor performance check
?1.
Turn the ignition switch to ON (II), or press the engine start/stop button to select the ON mode.

?2.
Check the parameter(s) below with the HDS.
Signal
Malfunction Threshold
Current conditions
Values
Unit
Values
Unit
MAP SENSOR
Less than 54.1
kPa
    
Less than 1.61
V

Did the value maintain the malfunction threshold for 5 seconds or more?

     
YES
     
     
     
     
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 (A/T in P or N, M/T 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
A/T in D, M/T in 4th or 5th
Vehicle speed accelerated to 15 mph (24 km/h) or more under half throttle

Signal
Current conditions
Values
Unit
ECT SENSOR 1
    
ENGINE SPEED
    
VEHICLE SPEED
    

?4.
Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.
DTC Description
OBD STATUS
P1128 MAP Sensor Signal Lower Than Expected
  

Does the HDS indicate FAILED?

     
YES
     
     
     
The failure is duplicated. Replace the MAP sensor, 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 PCM. 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), or press the engine start/stop button to select the ON mode.

?2.
Reset the PCM with the HDS.


?3.
Do the PCM idle learn procedure.

?4.
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.

?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
A/T in D, M/T in 4th or 5th
Vehicle speed accelerated to 15 mph (24 km/h) or more under half throttle

Signal
Current conditions
Values
Unit
ECT SENSOR 1
    
ENGINE SPEED
    
VEHICLE SPEED
    

?6.
Monitor the OBD STATUS for DTC P1128 in the DTCs MENU with the HDS.
DTC Description
OBD STATUS
P1128 MAP Sensor Signal Lower Than Expected
  


Does the HDS indicate PASSED, FAILED, or NOT COMPLETED?

     
PASSED
     
     
     
Troubleshooting is complete. If any other Pending or Confirmed DTCs are 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.