MAP Sensor Circuit Diagnosis

Schematic:

CIRCUIT DESCRIPTION

The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold vacuum. The MAP sensor signal voltage to the PCM varies from below 2.0 volts at idle to above 4.0 volts with the key on and the engine not running, or the engine running at Wide Open Throttle (WOT).

The MAP sensor is used to determine manifold pressure changes while the linear EGR flow test diagnostic is being run in order to determine the engine vacuum level for other diagnostics, and to determine Barometric Pressure (BARO). The PCM monitors the MAP signals for voltages outside the normal range of the MAP sensor. If the PCM detects a MAP signal voltage that is excessively high, DTC P0108 Manifold Absolute Pressure (MAP) Sensor Circuit High Voltage sets. If the PCM detects a MAP signal voltage that is excessively low, DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage sets.

The PCM also uses the MAP sensor for Throttle Position (TP) sensor performance. If the PCM detects a TP in an out of range condition when the MAP reading is above or below a calibrated amount, DTC P0121 Throttle Position (TP) Sensor Performance sets.

Steps 1 - 9:

Steps 10 - 14:

DIAGNOSTIC AIDS
Check for the following conditions:
^ Monitor the MAP sensor using the scan tool. If the MAP sensor does not respond to throttle changes, check the 3X reference circuits from the Ignition Control Module (ICM) to the PCM.
If the 3X reference signal is lost, the PCM will only update the MAP sensor reading once per key cycle when the engine is first started. Depending on where the MAP sensor voltage is when the engine is started, the high or low voltage MAP sensor DTCs will set.
^ A faulty connection at PCM-Inspect the harness connectors for backed-out terminals, improper mating, broken locks, improperly formed or damaged terminals, and faulty terminal to wire connections. Refer to Testing for Intermittent and Poor Connections and to Wiring Repairs in Diagrams.
^ Inspect the wiring harness for damage. If the harness appears to be OK, observe the MAP display on the scan tool while moving the connectors and the wiring harnesses related to the sensor. A change in the display indicates the location of the fault. Refer to Wiring Repairs in Diagrams.
^ Inspect for kinked and damaged vacuum hoses. Ensure that a good vacuum source is available. Refer to Emission Hose Routing Diagram.