Page 6E2-54 DOHC Code 23B MAT Sensor High Temp. Indicated

Fig. 6E2-35:

6E2-54 DRIVEABILITY AND EMISSIONS (DOHC)

CODE 23B

MANIFOLD AIR TEMPERATURE (MAT) SENSOR CIRCUIT (HIGH TEMPERATURE INDICATED)


Circuit Description:

The Manifold Air Temperature Sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage (4-6 volts) on CKT 472 to the sensor. When manifold air is cold, the sensor (thermistor) resistance is high, therefore, the ECM will see a high signal voltage. As the air warms, the sensor resistance becomes less and the voltage drops.

MAT HIGH Test Description:

Numbers below refer to circled numbers on the diagnostic chart.
(1) This check determines if the Code 23B is the result of a hard failure or an intermittent condition.
A Code 23B will set if:
^ A MAT temperature greater than 14~C is detected for a time longer than 4.25 minutes.

Diagnostic Aids:

If the engine has been allowed to cool to an ambient temperature (overnight), coolant and MAT temperatures may be checked with a "Scan" tool and should read nearly the same. A Code 23B will result if CKT's 472 or 42 become open, or shorted to ground. If Code 23B is intermittent, refer to Section "B".