Powertrain Controls - ECM/PCM

DTC 37 Chart:

CIRCUIT DESCRIPTION
The Intake Air Temperature (IAT) sensor is a thermistor. The PCM applies a voltage (about 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 warm, the sensor resistance is low causing the PCM to measure a low voltage. If the IAT sensor indicates too high of a temperature,the PCM will set DTC 37.

DTC 37 WILL SET WHEN
- DTC 14 or 15 are not set.
- Engine coolant temperature is below 100°C (212°F).
- Intake air temperature sensor signal indicates temperature above 148°C (297°F).

ACTION TAKEN (PCM WILL DEFAULT TO)
With a current DTC 36 set, the PCM will illuminate the Malfunction Indicator Lamp (MIL) (Service Engine Soon) and disable the EGR system for the entire ignition cycle.

DTC 37 WILL CLEAR WHEN
The fault no longer exists.

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

1. This step determines if DTC 37 is the result of a hard failure or an intermittent condition.
2. If the PCM recognizes the open circuit (high voltage) and displays a low temperature, the PCM 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 about the same.
- It DTC 37 is intermittent or a "Hard Start" symptom is present, check intake air temperature with a scan tool on a cool engine. Temperature should display within 5° of the ambient.