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.
1989 Geo Tracker L4-1590cc 1.6LFACTORY OEM SERVICE PROCEDURE
Coolant Temperature Sensor/Switch (For Computer): Description and Operation
MAT & CTS Sensor Characteristics:
Located at the side of intake manifold, this sensor measures the temperature of the engine coolant and converts its change into a resistance through the thermistor similar to the Manifold Air Temperature (MAT) sensor. That is, as coolant temperature lowers, resistance increases and as it rises, resistance decreases. By monitoring the resistance of the CTS, the ECM detects the engine coolant temperature.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.