Diagnostic Aids:

The MAT sensor is a thermistor or variable resistor that varies in resistance with temperature. The MAP sensor is a 2-wire sensor with a reference or signal voltage coming from the ECM to sensor pin B circuit No. 473 and a sensor reference ground on pin A circuit No. 476.

As temperature of sensor increases, sensor resistance is lower. The signal voltage from ECM to pin B decreases as sensor temperature increases, because current flows from pin B through the sensor element to pin A ground sensor. Voltage is dropped across the sensor element.

High temperature means low signal voltage on circuit No. 472, and low temperature means high signal voltage on circuit No. 472. Code "EO37", shorted MAP sensor, sets because ECM assumes that MAP can not be 288°F (142°C) or greater with a coolant of less than 221°F (105°C).

NOTE: The following step numbers refer to the numbers in the accompanying flow chart(s).

With a shorted sensor, ECM parameter code "ED05" should read 288°F (142°C) or greater. If not, sensor is not shorted. See NOTES ON INTERMITTENTS.
Check for sensor shorted or circuit No. 472 shorted. If ECM parameter P.0.5. stays at 288-304°F (142-151°C) with sensor unplugged, short is in circuit No. 472.
Fault is at ECM connector or ECM. Before ECM is replaced, perform PERFORMANCE CHART C1 - ECM REPLACEMENT CHECK at the end of this article.
MAT sensors can be damaged by a backfire at intake. If vehicle has had more than one MAT sensor replaced, check for signs of backfire or high intake manifold temperatures due to improper valve train operation.