DTC 23

Intake Air Temperature Sensor Circuit:

Circuit Description:
The Intake Air Temperature (IAT) sensor is a thermistor. The PCM applies 5 volts on CKT 472 to the sensor.

When the air is cold, the sensor resistance is high, and the PCM will measure a high signal voltage. If the air is warm, the sensor resistance is low causing the PCM to measure a low voltage.

Code 23 will set if:

^ Coolant Temperature greater than 60°C (140°F).
^ Mass Air Flow less than 12 gm/sec.
^ Vehicle speed less than 25 mph.
^ IAT signal voltage indicates an intake air temperature below -34°C (-29°F) for 5 seconds.

Code 23 does not illuminate the "Service Engine Soon" light.

Code 23 Diagnostic Chart:

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

1. A Code 23 will set due to an open sensor, wire, or connection. An open circuit would cause the Tech 1 to display approximately -40°C (-40°F). This test determines if the wiring and PCM are OK.


Diagnostic Aids:
An intermittent may be caused by a poor connection, rubbed through wire insulation or a wire broken inside the insulation.

Check For:

^ Poor Connection or Damaged Harness Inspect PCM harness connectors for backed out terminals "BA7" and/or, "BB7", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection, and damaged harness.

^ Intermittent Test - Observe Intake Air Temperature (IAT) on Tech 1 while moving related connectors and wiring harness with warm engine running. If the failure is induced, the lAT display will change to a 400 temperature reading. This may help to isolate the location of the malfunction.