DTC 23

DTC 23 - Intake Air Temperature (IAT) Sensor Circuit (Low Temperature Indicated):

TPS Sensor, ECT Sensor, IAT Sensor Wiring 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.

DTC 23 will set if:
^ Engine coolant temperature is greater than 60°C (140°F).
^ Mass air flow less than 12 g/sec.
^ Vehicle speed less than 25 mph.
^ lAT signal voltage indicates an intake air temperature below -34°C (-29°F) for 5 seconds.
DTC 23 does not illuminate the MIL (Service Engine Soon).

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

1. A DTC 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 I while moving related connectors and wiring harness with warm engine running. If the failure is induced, the IAT display will change to a -40° temperature reading. This may help to isolate the location of the malfunction.