The IAT sensor is supplied with a 5 V reference signal at Pin 1 through 12–pin connector (Pin 5) from
ECM Pin X1–7. The sensor is grounded at Pin 2 through the signal ground at ECM Pin X4–24. As the air temperature increases or decreases, the sensor changes resistance and provides the air temperature
signal voltage at the ECM. The signal voltage is monitored by the ECM to determine the intake air temperature.
Fault Detection / Management
When the ECM detects an IAT signal out of range high or low, the ECM will ignore the IAT signal and assume
an ambient temperature of 25 °C (77 °F).
IAT Diagnostic Trouble Codes (DTCs)
DTCs are read using the EST or by counting the flashes from the amber and red ENGINE lamp on the vehicle dash.
DTC 154
IAT signal out-of-range low
• DTC 154 is set by the ECM if signal voltage is less than 0.127 V for more than 0.35 second.
• DTC 154 can be set due to a short to ground in the signal circuit or a failed IAT sensor.
• When DTC 154 is active, the amber ENGINE lamp is illuminated.
DTC 155
IAT signal out-of-range high
• DTC 155 is set by the ECM if signal voltage is more than 4.6 V for more than 0.35 second.
• DTC 155 can set due to an open signal or ground circuit, a short to a voltage source, or a failed IAT sensor.
• When DTC 155 is active, the amber ENGINE lamp is illuminated.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
• Digital Multimeter (DMM)
• 3-Banana Plug Harness
• 500 Ohm Resistor Harness
• Breakout Box
• Breakout Harness
• Terminal Test Adapter Kit
