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The intake air temp is higher than it should be. The temp will slowly climb while the engine is running or if the ignition key is on. The sensor is good, and I have a spare just in case. It's a basic thermistor which pulls the 5v down as the temp climbs. The voltage readings at the sensor and PCM are accurate. I have tried two different types of OBD2 software to verify that the temp is reading high. The engine starts and runs fine for about 15 minuets, but as the intake air rises, the engine will miss and ping. I tried both sensors, unplugged the sensor, and unplugged the battery for a day. But the problem remains. The temp will usually be in the 40s and climb over 100. It never throws a code for the sensor unless its unplugged.
I recently purchased this vehicle. They had replaced a plug and coil because the tip off the plug had broken. After driving it a few times the plug backed out and melted the plug and coil. I tapped the head and installed a plug insert along with a Delphi coil. It was after doing this that I noticed the intake air issue.
At this point I am leaning towards a PCM...... but I find it strange that " all of a sudden" it failed. Any help would be greatly appreciated!!
temp will slowly climb while the engine is running or if the ignition key is on.
With engine cold KOEO the air intake temp rises slowly? Should read steady ambient air temp. If wiring tests good, ie 5v sig and <100mv ground has to be bad sensor.
Could have two bad sensors. Have you tried to bench test the sensors?
Only other thing I can think of is the sensor signal wire is being influenced by some other variable resistor.
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Voltage is being measured at the ecm and the sensor. Unplugged is near 5v. Plugged in, it is around 2.7v. I can make the voltage go lower on both sensors by adding warm air near the sensor. The correct voltage is at the sensor and ecm. But the temp reading from the ecm is always going up. It tops off somewhere above 100 degrees.
If I leave the ignition off, or disconnect the battery long enough, the temp reading will go back to the 40 degree range. Note that the whole time, the voltage stays the same. So the temp reading off the cam climbs while the voltage stays the same.
You may want to connect a (variable) resistor/potentiometer in the place of the sensor and simulate different temps to confirm or discard a sensor problem.
Just to make sure: on a cold engine, koeo, the voltage reading with a dvom stays the same but the scanner shows rising temp?
With the sensor unplugged you initially probably will read around -40 degrees. Does the temperature reading rise as well with a disconnected sensor?
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As I had said originally, unplugging the sensor does not change anything. The temp still continues to increase. And I have used heat cold and air to change the voltage output of the sensor. I can even jump the terminals together and yet the pcm still displaces the same reading. It will start around 40 degrees and rise the longer the ignition is on until it hits above 100 degrees.
