W 250 Pickup L6-359 5.9L DSL (1989)
Intake Air Temperature Sensor: Testing and Inspection
Thermistor Electrical Connections
1.
Disconnect the 2-Way thermistor electrical connector.
2.
Turn the ignition switch to the ON position.
3.
The following should occur:
^
The Wait-To-Start light will illuminate and the air intake heater solenoids will click (The air intake heater solenoids should click every time
the Wait-To-Start light illuminates).
^
The Wait-To-Start light will remain illuminated for 20 seconds. After 20 seconds, the Wait-To-Start light will turn off and the air intake
heater relays will click off.
^
The Wait-To-Start light will remain off for another 20 seconds, then the Wait-To-Start light will start flashing. The light starts flashing to
indicate that the thermistor circuit is open (because the electrical connector is disconnected).
If the light does not perform exactly as previously outlined, there is a problem with the wiring harness or the control module. If the light performs
exactly as outlined, go to step 4.
4.
Connect a voltmeter to the KSB (cold start) solenoid valve wire terminal and ground. No voltage should be present at the KSB valve. If voltage is
at the KSB valve, there is a short in the wiring harness or the control module is defective.
5.
If all of the previous steps prove the thermistor control system to be working properly when the thermistor is disconnected, and the air intake
heater system or KSB system doesn't work properly when the thermistor is connected, replace the thermistor.
