DTC 23
Code 23 Chart:
Wiring Diagram For MAT/IAT Sensor:
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 (5.0 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 engine has been running longer than two minutes.
b. The signal voltage indicates a IAT reading of less than -38°C (-36°F).
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 469. If circuit 469 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 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 469 becomes open. If Code 23 is intermittent, see DIAGNOSIS BY SYMPTOM.