DTC 23

Code Chart 23:

IAT Sensor Circuit:

CIRCUIT DESCRIPTION:
The Intake Air Temperature (IAT) sensor uses a thermistor to control the signal voltage to the ECM. The ECM applies a voltage (about 5 volts) on CKT 472 to the sensor. When the air is cold, the sensor (thermistor) resistance is high, therefore the ECM will see a high signal voltage. If the air is warm, the sensor resistance is low, therefore, the ECM will see a low voltage.

The IAT sensor is located in the air cleaner.

TEST DESCRIPTION: Number(s) below refer to circled number(s) on the diagnostic chart.

1. DTC 23 will set if:

^ A signal voltage indicates an intake air temperature below -35°C (-31°F) for 10 seconds.
^ Time since engine start is 4 minutes or longer.
^ No VSS.

2. A DTC 23 will set due to an open sensor, wire or connection. This test will determine if the wiring and ECM arc OK.

3. This will determine if the signal CKT 472 or the sensor ground, CKT 452 is open.

DIAGNOSTIC AIDS:
A scan tool reads temperature of the air entering the engine and should read close to ambient air temperature when engine is cold and rises as underhood temperature increases.

A faulty connection, or an open in CKT 472 or 452 will result in a DTC 23. - Intermittent Malfunctions