Hard Trouble Code E38: Notes

NOTE: If this code is not displayed during second pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure.

Trouble code E38 indicates that MAT sensor signal voltage is too high. This situation can be observed in engine data display parameter "P.0.5" as reading of B40°C to B35°C. Possible causes of this condition are: Open MAT sensor, defective wiring, terminals, etc., or ECM is not able to process signals properly.

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

If opposite condition (shorted MAT signal) can be created, the self-diagnostics can be used to detect failure by displaying engine data parameter "P.0.5". With opposite condition created, parameter "P.0.5" should display reading of 148-151°C. To create shorted sensor signal, disconnect MAT sensor and jumper harness terminals together. If reading is now 148-151°C, ECM and wiring harness are okay. Fault must be in sensor connector or MAT sensor itself.
If reading is 147°C or less, then there is an open in signal circuit No. 472, in sensor ground circuit No. 476X, or in ECM. If reading is now 148-151°C with circuit No. 472 jumpered to ground, an open exists in circuit No. 476X.
If reading remains 147°C or less with circuit No. 472 jumpered to ground at ECM, either ECM connector or ECM is faulty. If reading is now 148-151°C, an open exists in circuit No. 472.