Coolant Temp Sensor on 99+ Grand Am Testing

[xeroinfinity]

This works on 99'+ N-Bodies,
but is relevant to most N body temp sensors vs. resistance values.

Heres a pic of the coolant temp sensor,
and it located right under the TB on the V6(3.1 & 3.4L) easy to see and get to.
Easy to locate on the 4cyl(2.4L) too.

V6 temp sensor

4 Cyl Temp sensor

Testing your Coolant temp sensor is as follows;

- First inspect the wires at the plug for looseness or breaks.

- Now test the circuit for power from the PCM.
- Disconnect the plug-in on the sensor and test the two terminals on the wire harness.
- Connect the + lead on the voltmeter to #1 and the ground to #2.
- Turn the key on, should read approx 5 volts.

- If not check the wiring from the plug to the pcm.
- If the cicuits are good have the PCM checked by a dealership or other qualified shop.

Checking the resistance values



- With the ignition off and engine cold, unplug the sensor connector.
- Using an Ohmmeter measure the resistance between the terminals on the sensor cold(between 50-80 deg). Write that # down.

- Start the engine and let it get to running temp between 180-200deg.
- Disconnect the connector and test the resistance again.
- Compare the two measurments to the chart below.

- If the results are incorrect then replace the sensor.

- When replacing the sensor use teflon tape to seal from leaks.

Hope that helps.