Coolant Temperature Sensor/Switch (For Computer): Testing and Inspection

Coolant Temperature Sensor Schematic:

A faulty coolant temperature sensor will set code 21 in the on-board diagnostic system. Refer to the schematic diagram and test the coolant sensor with the diagnostic chart.

Wire color code identification:

L: Blue
B: Black
Y: Yellow
G: Green
R: Red
W: White
Br: Brown
Lg: Light green
Gr: Gray

Coolant Temperature Sensor Diagnostic Chart:

COOLANT TEMPERATURE SENSOR DIAGNOSTIC CHART