DTC 31

Code 31:

Code 31:

CIRCUIT DESCRIPTION:

The Mass Air Flow (MAF) Sensor measures the flow of air, which passes through it in a given time. The ECM uses this information to monitor the operating condition of the engine in calculating fuel delivery. A large quantity of air movement indicates acceleration, while a small quantity indicates deceleration or idle. The MAF sensor produces a frequency signal, which cannot be easily measured. The sensor can be diagnosed using the procedures on this chart. The MAF sensor also contains the Manifold Air Temperature (MAT) sensor and provides the ground to the circuit opening relay to run the fuel pump once the engine has started.

TEST DESCRIPTION: Numbers below refer to circled numbers on the diagnostic chart.

1. Verifies B+ and ground at MAF sensor.

2. Verifies proper voltage control to the ECM from MAF sensor.

3. Verifies proper voltage from MAF sensor with rpm.

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. Also check for a damaged MAF housing.