DTC 38

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, 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 drop from its normal value to an open reading of (-) 40° to (-) 35° C.
Code 38 indicates that the manifold air temperature (MAT) sensor signal received by ECM is too high. Possible causes of this condition are as follows:
a. An open MAT sensor.
b. Defective or improperly connected wiring.
c. ECM cannot process signal.
To diagnose a Code 38, proceed as follows:
1. Turn ignition on, enter diagnostics and display parameter .0.5. Failure code will be verified by reading of (-) 40 to (-) 35° C.
2. Disconnect sensor connector and place jumper wire across harness terminals.
3. If value of parameter .0.5 is 148 to 151, check for poor mating of sensor terminals or a faulty MAT sensor and repair or replace as necessary.
4. If value of parameter .0.5 is 147 or less, remove jumper wire from terminals and jumper inside harness terminals (circuit 472) to ground. If value of parameter .0.5 is 148 to 151, inspect circuit 476-Y for an open and repair as necessary.
5. If value of parameter .0.5 is 147 or less, remove jumper wire and jumper pin 21 of blue connector to ground.
6. If value of parameter .0.5 is 148 to 151, inspect circuit 472 for an open and repair as necessary. If value of parameter .0.5 is 147 or less, fault is in ECM or ECM connector.