P1107

DTC P1107 Manifold Absolute Pressure Intermittent Low Voltage




Circuit Description
The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP signal voltage to the engine control module (ECM) varies from below 2 volts at idle (high vacuum) to above 4 volts with the key in the ON position, engine not running or at wide open throttle (WOT) (low vacuum).

A "speed density" method of determining engine load is used. This is calculated using inputs from the MAP sensor, the rpm (58X), and the Intake Air Temperature (IAT) sensor. The MAP sensor is the main sensor used in this calculation, and measuring engine load is its main function.

The MAP sensor is also used to determine manifold pressure changes while the linear Exhaust Gas Recirculation (EGR) flow test diagnostic is being run (refer to DTC P0401). This determines engine vacuum level for some other diagnostics and determines barometric pressure (BARO). The ECM compares the MAP sensor signal to calculated MAP based on throttle position (TP) and various other engine load factors. If the ECM detects a MAP signal voltage that is intermittently above the calculated value, DTC P1107 will set.

Conditions for Setting the DTC
- Engine running.
- No TP sensor DTCs are present.
- The MAP is less than 103 kPa.
- TP sensor is greater than or equal to 2% if rpm is less than or equal to 2000.
- TP sensor is greater than 5% if rpm is greater than 2000.

Action Taken When the DTC Sets
- The Malfunction Indicator Lamp (MIL) will not illuminate.
- The ECM will store conditions which were present when the DTC was set as Failure Records data only.
- This information will not be stored in the Freeze Frame data.

Conditions for Clearing the MIL/DTC
- A history DTC will clear after 40 consecutive warm-up cycles without a fault.
- DTC P1107 can be cleared by using the scan tool CLEAR INFO function or by disconnecting the ECM battery feed.

Steps 1 - 8:

Diagnostic Aids
Check for the following conditions:
- Leaking or plugged vacuum supply line to the MAP sensor.
- Inspect ECM harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and poor terminal-to-wire connection.
- Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving connectors and wiring harnesses related to the sensor. A change in the display will indicate the location of the fault.

Reviewing the Fail Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.