GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2005 🢒 Epica 🢒 DTC 🢒 DTC 023

Circuit Description

The intake air temperature (IAT) sensor is a thermistor which measures the temperature of the air entering the engine. The electronic control module (ECM) applies 5 volts through a pull-up resistor to the IAT sensor. When the temperature is cold, the IAT sensor resistance is high and the ECM will monitor a high signal voltage on the IAT circuit. If the intake air is warm, the sensor resistance is lower, causing the ECM to monitor a lower voltage.

Conditions for Setting the DTC
    • The engine has been running longer than 120 seconds.
    • The IAT sensor signal voltage indicates a temperature above 146°C (295°F).

Diagnostic Aids

Inspect the wiring harness for damage. If the harness appears to be OK, observe the IAT sensor display on the scan tool while moving the connectors and the wiring harnesses related to the IAT sensor. A change in the display will indicate the location of the fault.

Step

Action

Values

Yes

No

1

Was the Diagnostic System Check performed?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Connect the scan tool to the data link connector (DLC).
  2. Run the engine until it reaches operating temperature.

Does the scan tool show the intake air temperature (IAT) sensor reading within the value specified?

10-80°C (50-176°F)

Go to Diagnostic Aids

Go to Step 3

3
  1. Turn the ignition to LOCK.
  2. Disconnect the IAT sensor connector.
  3. Turn the ignition ON.

Does the scan tool show the IAT sensor reading below the value specified?

-35°C (-31°F)

Go to Step 4

Go to Step 5

4

Inspect for a faulty connector or terminals at the IAT sensor connector.

Is the problem found?

--

Go to Step 7

Go to Step 8

5

Inspect the wire for a short to ground between the IAT connector terminal 2 and the engine control module (ECM) connector terminal D15.

Is the problem found?

--

Go to Step 7

Go to Step 6

6

Inspect the wire for a short to ECM reference voltage between the IAT connector terminal 1 and the ECM connector terminal B4.

Is the problem found?

--

Go to Step 7

Go to Step 9

7
  1. Turn the ignition to LOCK.
  2. Repair the wire or the connector terminal as needed.
  3. Clear any DTCs from the ECM.
  4. Run the engine until it reaches operating temperature.
  5. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

Go to Step 2

8
  1. Turn the ignition to LOCK.
  2. Replace the IAT sensor. Refer to Intake Air Temperature Sensor Replacement .
  3. Clear any DTCs from the ECM.
  4. Run the engine until it reaches operating temperature.
  5. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

--

9
  1. Turn the ignition to LOCK.
  2. Replace the ECM. Refer to Engine Control Module Replacement .
  3. Run the engine until it reaches operating temperature.
  4. Perform the Diagnostic System Check.

Is the repair complete?

--

System OK

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