MAP Sensor Circuit Diagnosis

Diagnostic Chart (Part 1 Of 2):

Diagnostic Chart (Part 2 Of 2):

Schematic:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure (vacuum). The MAP sensor signal voltage to the PCM varies from below 2 volts at idle (high vacuum) to above 4 volts with the key ON, engine not running or at wide-open throttle (low vacuum). The MAP sensor is used to determine manifold pressure changes while the EGR flow test diagnostic is being run, refer to DTC P0401 Exhaust Gas Recirculation (EGR) Flow Insufficient. Also to update the barometric pressure reading (BARO), and as an enabling factor for other diagnostics. 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 will be set. If the PCM detects a MAP signal voltage that is excessively low, DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage will be set. P0401

DIAGNOSTIC AIDS
Check for the following conditions:
^ Monitor the MAP sensor using a scan tool. If the MAP sensor does not respond to throttle changes, check the 3X reference circuits from the ignition control module 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 (high voltage or low voltage) is when the engine is started, the high or low voltage MAP sensor DTCs will set.

^ Poor connection at PCM - Inspect harness connectors for the following conditions:
- Backed out terminals
- Improper mating
- Broken locks
- Improperly formed or damaged terminals Poor terminal to wire connection

Refer to Testing for Intermittent and Poor Connections and Connector Repairs in Diagrams.

^ Damaged harness - 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. 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 in Diagrams.

TEST DESCRIPTION
The numbers below refer to the step numbers on the diagnostic table.
13. This vehicle is equipped with a PCM which utilizes an Electrically Erasable Programmable Read Only Memory (EEPROM). When the PCM is being replaced, the new PCM must be programmed.