Advanced Diagnostics

Advanced Diagnostics - DTC P1128: Manifold Absolute Pressure (MAP) Sensor Signal Lower Than Expected











General Description
The manifold absolute pressure (MAP) sensor senses manifold absolute pressure (vacuum) and converts it into electrical signals. The MAP sensor outputs low signal voltage at high vacuum (idling) and high signal voltage at low vacuum (throttle valve wide open). The powertrain control module (PCM) compares a predetermined MAP value at a given throttle position and manifold absolute pressure to the output voltage value of the MAP sensor. If the MAP sensor outputs lower voltage than expected, the PCM detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The MAP sensor output is 53 kPa (15.9 inHg, 404 mmHg) or less for at least 2.0 seconds when atmospheric pressure is 103 kPa (30.6 inHg, 776 mmHg).

Driving Pattern
1. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on.
2. Drive the vehicle at a speed of 15 mph (24 km/h) or more under Enable Conditions (see Throttle position ) for at least 5 seconds.

- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.