Powertrain Controls - ECM/PCM

Code Chart 23:

CHART 1 OF 2

DTC 23 Intake Air Temperature Sensor Circuit (High/Low Temperature):

CHART 2 OF 2

Intake Air Temperature Sensor Wiring Circuit:

Circuit Description:
The Intake Air Temperature (lAT) sensor, located in the air cleaner assembly, uses a thermistor to control the signal voltage to the Engine Control Module (ECM). The ECM applies a reference voltage (5 volts) on CKT 472 to the sensor. When intake air is cold, the sensor (thermistor) resistance is high. The ECM will then sense a high signal voltage. As the air warms, the sensor resistance becomes less and the voltage drops.

DTC 23 Will Set When:
^ Engine running for 2 minutes or longer
^ Signal voltage indicates an lAT temperature less than -39°C (-39.4°F) or greater than 146°C (294°F).

Action Taken (ECM will default to): Malfunction Indicator Lamp (MIL) illuminates. ECM will default to -5.5°C, for intake air temperature (Tech I scan tool will not show defaulted value).

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.
1. This step checks to see if DTC 23 is the result of a hard failure or an intermittent condition.
2. If the scan tool displays a high temperature, the ECM and wiring are OK.
3. This step checks continuity of CKT 472 and CKT 452. If CKT 452 is open, there may also be other DTC(s) stored.
4. This step determines if DTC 23 is the result of a hard failure or an intermittent condition.
5. If the ECM recognizes the open circuit (high voltage) and displays a low temperature, the ECM and wiring are OK.

Diagnostic Aids:
If the engine has been allowed to cool to an ambient temperature (overnight), engine coolant and intake air temperatures may be checked with a Tech 1 scan tool and should display values close to each other.
^ If DTC 23 is intermittent or a "Hard Start" symptom is present check intake air temperature with a scan tool on a cool engine. Temperature displayed should be within 5 degrees of the ambient. If not, check the IAT sensor. if sensor is OK. check connections. If connections at sensor and ECM are OK, replace ECM.