DTC 23

Code 23 Diagnostic Chart:

Wiring Diagram For MAT/IAT:

CIRCUIT DESCRIPTION:

The Intake Air Temperature (IAT) Sensor uses a thermistor that controls the signal voltage to the ECM. The ECM applies a reference voltage (4.0-5.5 volts) on circuit 472 to the sensor. When the air is cold, the sensor (thermistor) resistance is high, therefore the ECM will sense a high signal voltage. If the air is warm, the sensor resistance is low, therefore the ECM will see a low voltage.


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

1. This checks to see if a Code 23 is the result of a hard code failure or an intermittent problem.
A Code 23 will set under the following conditions:
a. The signal voltage indicates a IAT reading of less than -30°C (-22°F).
b. The engine has been running longer than 58 seconds.

2. Simulates a Code 25. If the "Scan" tool displays a high temperature, the ECM and wiring are OK.

3. This step checks the continuity of circuits 472 and 802. If circuit 802 is open, there may be a Code 33 stored.


DIAGNOSTIC AIDS:

1. If the engine has been allowed to cool to ambient temperature, coolant and MAT/IAT temperatures may be checked with a "Scan" tool. The readings should be close to each other.
2. A Code 23 will result if circuits 472 or 802 becomes open. If Code 23 is intermittent, refer to Diagnosis by Symptoms.