Part 2 of 2

Code Chart 23:

Intake Air Temperature Sensor Wiring:

CIRCUIT DESCRIPTION
The Intake Air Temperature (IAT) 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 (4 to 5.5 volts) on CKT 472 to the sensor. When intake air is cold, the sensor (thermistor) resistance is high. Therefore, the ECM will sense a high signal voltage. As the air warms, the sensor resistance becomes less and the voltage drops.

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

1. This step determines if DTC 23 is the result of a hard failure or an intermittent condition.

2. 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 scan tool and should read 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 using the "Diagnostic Aids".