DTC 37

Fig. 14 Coolant sensor wiring circuit:

If this code is not displayed during the third pass of diagnostic codes, the problem is an intermittent failure. To help isolate the problem, manipulate related wiring while observing parameter .0.5. If failure is induced, MAT reading will jump from its normal value to a shorted reading of 142°-151° C.
Code 37 indicates that the manifold air temperature (MAT) sensor signal received by ECM is too low. Possible causes of this condition are as follows:
a. A shorted MAT sensor.
b. Defective or improperly connected wiring.
c. ECM cannot process signal.

To diagnose a Code 37, proceed as follows:
1. Turn ignition on, enter diagnostics and display parameter .0.5. Failure code will be verified by reading of 142 to 151° C.
2. Disconnect sensor connector. If value of parameter .0.5 is (-) 40 to (-) 35, replace MAT sensor.
3. If value of parameter is (-) 34 or more, proceed as follows:
a. Turn ignition off and disconnect red ECM connector.
b. Turn ignition on, enter diagnostics and display parameter .0.5.
c. If parameter value does not change, replace ECM.
4. If value of parameter is (-) 34 or more, check circuit 472 for short to ground or short to circuits 476 X and Y. If circuit is satisfactory, check for faulty ECM connector or ECM.