DTC 31

MAP Sensor Circuit:

CIRCUIT DESCRIPTION
The Manifold Absolute Pressure (MAP) Sensor responds to changes in manifold pressure (vacuum). The ECM receives this information as a signal voltage that will vary from about 1 to 1.5 volts at closed throttle idle, to 4-4.5 volts at wide open throttle. If the MAP Sensor fails, the ECM will substitute a fixed MAP value to control fuel delivery.

A CODE 31 WILL SET WHEN
1. MAP signal voltage is too low (less than 1.6 in. Hg) for 0.2 seconds.

TEST DESCRIPTION
Numbers below refer to circled numbers on the diagnostic chart:
1. This step determines if Code 31 is the result of a hard failure or an intermittent condition.
2. Jumpering harness terminals "B" to "C," 5 volts to signal, will determine if the sensor is at fault, or if there is a problem with the ECM or wiring.

DIAGNOSTIC AIDS
An intermittent may be caused by a poor connection rubbed through wire insulation or a wire broken inside the insulation. Inspect ECM harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.