Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1998 Hummer H1 V8-6.5L DSLFACTORY OEM SERVICE PROCEDURE
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
Figure 3-11: Coolant Temperature Sensor Circuit:
Engine Coolant Temperature Sensor Test
The coolant temperature sensor is a thermistor that provides a temperature signal to the PCM (Figure 3-11). The signal is in the form of a voltage that changes according to sensor resistance. At low temperatures, resistance and voltage are both high. As temperature increases, resistance and voltage both decrease.
A sensor fault will cause the check engine light to illuminate and the torque converter clutch to apply early. If the sensor fails in a cold mode, it can produce overrich operation and rough idle.
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.