2000 Malibu - 3.1 Liter - Air Intake Temp Sensor

[Fishinguy40]

The check engine light came on. Hook up the code reader from the parts store and it says air intake temp sensor high. Sorry I don't remember the exact error code.

I pulled the filter house and put a multimeter across the pins on sensor and read infinite resistance. I'm assuming this is an RTD and that the resistance will correlate to temperature. I also checked for voltage at the plug/wire harness with the car running and got 0.

I'm confident I got good a connection on the sensor pins when I tried to read resistance. So if it is an RTD, this would indicate that it is open/bad. I'm not as confident on my connections to the wiring harness plug. I will chack again and use a paper clip or something similar to insert into the plug to ensure I am getting a good connection when I check for voltage.

My questions are:

Should I expect 12 volts at the plug to the temp sensor? If not what voltage should I see?

Am I correct in assuming the temp sensor is an RTD and I should be able to read resistance?

What effect does the temp sensor have on performance? I would assume it is used to trim or fine tune the fuel/air ratio. It hasn't had any noticeable le effect on driving.

[Jeremy airjer W]

The IAT (intake air temp) sensor is a thermistor. As temp goes up resistance goes down.

Whats an RTD?

You should see a five volt reference on one wire and ground on the other.

You should see a resistance value anytime you ohm check the sensor.

The computer uses IAT and MAP (mass air pressure) to calculate air mass.

[Fishinguy40]

RTD stands for Resistance Temperature Detector.

RTD's and thermocouples are very common temperature measurement elements in the industry that I work in. So I resorted to what I know.

Like a thermistor, the resistance varies according to temperature but construction is different. RTD's are usually made from metals such as platinum.

Looks like I need a new thermistor and I will check for the 5V reference voltage.

Thanks Airjer!

[Fishinguy40]

It ended up being the wire connector. I bought a new sensor and brought it home. I decided to check the resistance of the new one but it read infinite.

Then I stuck a piece of 18 ga solid copper wire into the wiring connector to check for the +5v. I could only read 1 or 2 volts. As I was attempting to scrape some insulation of the wire going into the connector the wire just pulled right out. So I checked and it had +5v.

I went back to the parts store with new and old sensors and the bad connector. I borrowed their cheap multimeter and check both the old and new sensors....what do you know... both were good. So much for my expensive Fluke that is supposed to auto range (Yes, I checked mine by touching leads together and it did indicate continuity).

Anyhow, auto store let me return the new sensor since it was never installed and I bought a new connector, soldered it into the wire harness and she's good to go.

Thanks for the info Airjer!