Intake Air Temp. Sensor Check...

[87_SR5]

'92 Corolla - 4cyl 4A-FE

I need to check to see if my Intake Air Temp. Sensor is bad or not, but I was unable to find any information in the manual I have. To check it, the manual says to put an ohm meter on the sensor itself...and that's it. It doesn't say anything about what kind of reading I should get.

Does anyone know how to tell if the sensor is bad (by checking with an ohm meter)?

I put my meter on it and came back with 1.9-2.1 KiloOhms, depending on the temp of the sensor. I don't know where to go from here.

I got the code telling me I had a short in the Intake Air Temp. Sensor circuit. So I want to make sure that the sensor is at fault and it has nothing to do with the wiring or ECU before I go out and buy this sensor.

If anyone can help me out, that would be great.

[cobrajet25]

I'd check the wiring first. Normally, a code will only set if there is an open circuit on the sensor itself (like if it is completely burned out). If you are still getting tempurature-variable resistance out of it, then chances are it is alright.

Make DOUBLE SURE that you have good connections at the connector for the sensor. If the connection is bad, then the ECM will think that the sensor is burned out and set the code. You might even try bypassing the connector just to see if that is where your problem is. Disconnect the sensor. Stick pins (like plain straight pins) through the wires on the ECM (harness) side of the connector. Make sure that the pins go through the metal part (middle) of the wires. Then take alligator clips and attach them to the pins. Take the other ends of the clips and touch them to the pins inside the sensor. Turn the car on, and see if your CEL goes out. If it does, then the problem is the connections inside the connector. If not, then it is either the sensor itself or the harness. You might try unplugging your ECM and plugging it back in again to see if the bad connection is at the ECM end of the equation. Good luck. Regards, Aaron

[87_SR5]

Originally Posted by cobrajet25

I'd check the wiring first. Normally, a code will only set if there is an open circuit on the sensor itself (like if it is completely burned out). If you are still getting tempurature-variable resistance out of it, then chances are it is alright.

Make DOUBLE SURE that you have good connections at the connector for the sensor. If the connection is bad, then the ECM will think that the sensor is burned out and set the code. You might even try bypassing the connector just to see if that is where your problem is. Disconnect the sensor. Stick pins (like plain straight pins) through the wires on the ECM (harness) side of the connector. Make sure that the pins go through the metal part (middle) of the wires. Then take alligator clips and attach them to the pins. Take the other ends of the clips and touch them to the pins inside the sensor. Turn the car on, and see if your CEL goes out. If it does, then the problem is the connections inside the connector. If not, then it is either the sensor itself or the harness. You might try unplugging your ECM and plugging it back in again to see if the bad connection is at the ECM end of the equation. Good luck. Regards, Aaron

Thanks for the reply.

I figured my sensor would be okay since I was getting readings from it. And I think my wiring is good also because I put the voltmeter on the plug (going to the ECU) and came back with a reading (a constant 4.94 volts...approx.). So if my wiring is good from the ECU to the plug...then it must be a connection????

I will try your method to make sure the connection is there. I posted about my problem before because my Idle Air Control Valve was acting up. Turns out the IACV is controlled by the readings taken from the Intake Air temp sensor. So I checked for codes (even though the engine light was not on) and came back with the code telling me this circuit was bad.

Could my Intake air temp sensor be bad, but still give me readings? (but just give the wrong ohm readings?)

Thanks for the help

[foodaa]

With a voltmeter, ground the black lead, red lead to IAT input wire. The PCM supplies the sensor with a 5V reference signal. If the temperature reading is low(cold), the voltage reading will be around 5V. As the temperature gets high(hot), the voltage will go down. You can get a hair dryer and heat up the sensor. You should see the voltage signal start high and start to go down. If it stays at 5V, check the ground.

BTW, don't Ohm the sensor without disconnecting the wires.