240trevor Posted June 20 Report Share Posted June 20 I have double and triple checked. My AN volt 2 INPUT wire is sending 5v. I have not seen anyone else with this issue in my research. While trying to diag my IAT seemingly not sending signal I checked voltage at the IAT connector and was surprised to find 5v to both pins. Assuming I may have accidently tied in 5v out to my AN temp wire somewhere along the line I went into the car and started probing around. I de-loomed my harness I built to wire in the monsoon to the factory engine harness and made sure the AN temp 2 was not spliced anywhere with +5out. I double checked that I selected the correct color wire and that the wire was pinned into the ECU correctly. It is confirmed that the AN Temp input 2-Yellow/Brown wire-PIN 16 is sending +5v. I even cut the yellow/brown wire fairly close to the ECU plug and confirmed +5v from the ECU. I am afraid there may be some sort of defect with the ECU. Quote Link to comment Share on other sites More sharing options...
Vaughan Posted June 20 Report Share Posted June 20 So Temperature sensors have a resistance that varies with temperature, most temperature sensors are NTC (Negative thermal Coefficient) where the hotter they are the lower the resistance across them. When wiring the temperature sensor you wire one side to sensor ground and the other to an An Temp or an An Volt input into the ECU. The An Temp inputs have a built in pullup to 5V and when using An Volt inputs you need to wire in an external pullup to 5v. This setup operates like a resistor divider where you have a fixed resistance from 5V to the ECU signal pin and a varying resistance (the temperature sensor) between the ECU signal pin and sensor ground. The colder the sensor gets the higher it's resistance and so the closer to 5V the ECU signal gets, the hotter the sensor gets the lower it's resistance and so the closer to signal ground the ECU signal gets. If you are seeing 5V on both sides of the temperature sensor plug while the sensor is plugged in this means your signal ground is not connected. Picture attached shows how an external pullup resistor is added, the An Temp inputs all have internal pullups connected in the same way. Also re-reading your post it reads like you might have deliberately wired it to have an An Temp on side of the temperature sensor and a 5V supply on the other side, if you have done this then you need to change the 5V supply to a signal ground. Quote Link to comment Share on other sites More sharing options...
240trevor Posted June 20 Author Report Share Posted June 20 Ok just to be clear, AN Volt input 2 actually outputs 5v? I would have expected the sensor to be connected to +5v out and the other side to be returned to AN temp. I wired it as suggested and the temp reading is now close to room temp. Now I just need to figure out why my oem ECT sensor is reading -40. Quote Link to comment Share on other sites More sharing options...
Vaughan Posted June 20 Report Share Posted June 20 An Volt 2 does not output anything. An Temp 2 has a built in configurable pullup to 5V 10 minutes ago, 240trevor said: I would have expected the sensor to be connected to +5v out and the other side to be returned to AN temp. You may expect that but that is not how that works. 10 minutes ago, 240trevor said: I wired it as suggested and the temp reading is now close to room temp. Now I just need to figure out why my oem ECT sensor is reading -40. How have you wired your ECT sensor? Quote Link to comment Share on other sites More sharing options...
240trevor Posted June 20 Author Report Share Posted June 20 37 minutes ago, Vaughan said: How have you wired your ECT sensor? @VaughanAnalogue Temp Input 1 is wired to pin 18 on the 62/63 sr20det ecu plug Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 20 Report Share Posted June 20 53 minutes ago, 240trevor said: Analogue Temp Input 1 is wired to pin 18 on the 62/63 sr20det ecu plug And is the other side of the sensor connected to sensor ground? Quote Link to comment Share on other sites More sharing options...
240trevor Posted June 20 Author Report Share Posted June 20 23 minutes ago, Adamw said: And is the other side of the sensor connected to sensor ground? @adam It is the factory wiring. Confirmed one of the two pins is 5v (unplugged) Checking for voltage across both pins (unplugged) reads .046v (I would expect this to read 5v if the ground was good but have already established I'm no electrical engineer) Already tried replacing the sensor with another I had around. Quote Link to comment Share on other sites More sharing options...
Adamw Posted June 20 Report Share Posted June 20 3 minutes ago, 240trevor said: Checking for voltage across both pins (unplugged) reads .046v (I would expect this to read 5v if the ground was good but have already established I'm no electrical engineer) Correct, it should measure 5V, so the ground side is not connected to ground somewhere. Quote Link to comment Share on other sites More sharing options...
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