Code 23A Intake Air Temperature (IAT) Sensor Circuit

LOW TEMPERATURE INDICATED




Circuit Description
The Intake Air Temperature (IAT) Sensor uses a Thermistor to control the signal voltage to the Engine Control Module (ECM). The ECM applies a voltage (4-6 volts) to BLU/BLK wire of the Sensor. When Manifold air is cold, the Sensor (Thermistor) resistance is high, therefore, the ECM will see a IAT signal. As the air warms, the Sensor resistance becomes less and the IAT signal drops.




Test Description (IAT Low)
Number(s) below refer to circled number(s) on the diagnostic chart.

1. This step checks to see if Diagnostic Trouble Code (DTC) 23A is the result of a hard failure or an intermittent condition. A DTC 23A will set if:
- Signal voltage indicates a IAT temperature less than -3O°C.
- Engine has been running for longer than 3 minutes.

2. This test simulates conditions for DTC 23B. If the "Scan Tool" displays a high temperature, the ECM and wiring are OK.
3. This step checks continuity of BLU/BLK and BLK/WHT wires. If BLK/WHT wire is open there may also be a DTC 21A.

Diagnostic Aids
- If the Engine has been allowed to cool to an ambient temperature (overnight), Engine Coolant and IAT may be checked with a "Scan Tool" and should read nearly the same.
- A DTC 23A will result if BLU/BLK or BLK/WHT wires become open.
- If DTC 23A is intermittent, refer to Diagnosis by Symptom. Symptom Related Diagnostic Procedures