E038

Code E038 - Manifold Air Temp Sensor (Low Temp. Indicated):

Temperature To Resistance Values:

Wiring Diagram for Code E038 - Manifold Air Temp. Sensor (Low Temp. Indicated):

CODE E038 - MANIFOLD AIR TEMP. SENSOR (LOW TEMP. INDICATED)

Circuit Description:

The Manifold Air Temperature (MAT) Sensor is a thermistor (a resistor which decreases in resistance as temperature increases) mounted in the air cleaner assembly. Low temperature produces a high resistance (100,000 ohms at -40°C/-40°F) while high temperature causes low resistance (70 ohms at 130°C/266°F).

The ECM supplies a 5-volt signal to the sensor through a resistor in the ECM and monitors this voltage. the voltage will be high when the manifold air is cold, and low when the air is hot. By monitoring the voltage, the ECM knows the manifold air temperature.

Code E038 will set if a signal voltage indicates a manifold air temperature less than -35°C (-30°F).

Possible causes of a Code E038 are:

a. A open MAT sensor
b. Faulty wiring or terminals
c. A faulty ECM

Manifold air temperature is one of the inputs used to control:

a. Fuel delivery
b. Spark Timing (ESC)
c. Idle (IAC)




Test Description: The following numbered steps correspond with the step numbers on the diagnostic chart.

1. With engine warmed up, MAT should be displayed somewhere between -30°C and 130°. If not, a MAT circuit fault is indicated.

2. If the "MAT" reading is 130°C or warmer, the problem is a faulty MAT sensor of ECM.

3. When MAT signal CKT 472 is jumpered to ground, the result should be a MAT display above 130°C. If not, an open in CKTs 472 or 452, or a faulty ECM is indicated.




Diagnostic Aids:

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

Check For:

a. Poor Connection or Damaged Harness - Inspect ECM harness connectors for backed out terminals "C11" or "D12", improper mating, broken locks, improperly formed or damaged terminals, poor terminal to wire connection and damaged harness.

b. Intermittent Test - If connections and harness checks out ok, monitor ED05 (MAT) display while moving related connectors and wiring harness. If the failure is induced, the "MAT" display will abruptly change. This will help to isolate the location of the malfunction.



c. Shifted Sensor - The "Temperature To Resistance Value" scale above may be used to test the MAT sensor at various temperature levels to evaluate the possibility of a "shifted" (mis-scaled) sensor which may result in driveability complaints.