Operation CHARM: Car repair manuals for everyone.
Manuals through 2025 now available!

Our trusted friends have launched a new website named LEMON, which has newer manuals. It also contains all the CHARM manuals.

LEMON is the spiritual successor to CHARM, I recommend you try it!

Link: lemon-manuals.la or lemon-manuals.org.ua

(Some people have issue connecting. LEMON is investigating. For now, use Firefox or change your DNS server)

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

A Tech 1 scan tool displays engine coolant temperature (ECT) in degrees. After the engine is started, the temperature should rise steadily to about 90°C (194°F) then stabilize when the thermostat opens. If the engine has not been run for several hours (overnight) the engine coolant and intake air temperature (IAT) sensor should be within 5 degrees of each other. A fault in the ECT sensor circuit should set a DTC P0117 or DTC P0118. The Diagnostic Trouble Code (DTC) charts also contain a chart to check for sensor resistance values relative to temperature. Testing and Inspection