Diagnostic Aids

NOTE: If this code IS NOT displayed during the third pass of diagnostic codes, it is an intermittent failure and cannot be diagnosed using this procedure. For an intermittent code, refer to NOTE ON INTERMITTENTS.

Trouble Code 14 indicates that the coolant sensor signal voltage is too low. This condition will be observed in engine data display as a "coolant temperature" reading (parameter .0.4) of 142°-151°C. Possible causes of this condition are:

A. A shorted coolant sensor.
B. Defective wiring, terminals, etc.
C. ECM not processing the coolant signal properly.

If the opposite failure mode (open sensor) is created, then the self-diagnostics can be used to detect this failure by displaying engine data parameter .0.4. With the opposite failure created, parameter .0.4 should display a "coolant temperature" reading of -40° to -35°C. To create an open sensor signal, disconnect the coolant sensor connector. If the "coolant temperature" reading is now -40° to -35°C the ECM and the wiring harness are OK. The fault must be in the coolant sensor itself. If the "coolant temperature" reading is -34°C or greater, then there is a short to ground in the wiring harness or the ECM.