Code 23 (1.6L Turbo) - Manifold Air Temperature (Mat) Sensor Circuit (Low Temperature Indicated): Notes

The MAT sensor uses a thermistor to control signal voltage to the ECM. The ECM applies 4-6 volts on Blue/Black wire to MAT sensor. When manifold air is cold, sensor resistance is high and ECM will see a high voltage. As air temperature increases, sensor resistance decreases and the voltage drops.

1. This determines if Code 23 is result of a hard failure or an intermittent condition. Code 23 will set if engine is running longer than 1 minute and signal voltage indicates a MAT temperature below -38°F (-39°C).
2. This step simulates conditions for a Code 25. If scan tester displays a high temperature, ECM and wiring are okay.
3. This step checks continuity of Blue/Black wire and Black/White wire. If Black/White wire is open, a Code 22 may be present.