Intake Air Temperature Sensor Wiring Harness (Related to CEL P0112)

[NyteEscape]

So I've gotten a CEL (P0112 Intake Air Temperature Circuit Low Input) and have been trying to figure it out. I picked up a new IAT sensor and swapped it out, but still get the same error code. I think it's the wiring harness now, but i'm not sure how to check. It leads into a bundle of wires which are covered which eventually lead through the firewall into the ECU. Any of you guys have an idea how I can check this? My intake air temp is currently stuck reading 143 degress C, which I believe is the reason my car is feeling sluggish.

[old guy]

Is the wiring harness to the plug covered in a sheath or can you see the two wires attached to the plug?

[NyteEscape]

i can see the two wires going to the plug. when i try to trace the wire to find the other side, it goes into a sheath which then leads to the firewall.

pics for reference:

[old guy]

I'm going to guess that you had you intake manifold off recently. Check the plug going to the thermostat. If the wiring harness to the thermostat is completely covered (no exposed wires) you have the two plugs reversed.

[NyteEscape]

old guy, you have no idea how much i love you right now. i've been struggling with this for 2 weeks.

i just replaced my thermostat and j-plug, so i had the manifold and everything around there off. never even realized they have very similar looking plugs.

thanks again, and if you're even down in DC, i owe you a beer or 6.

[old guy]

old guy, you have no idea how much i love you right now. i've been struggling with this for 2 weeks.

i just replaced my thermostat and j-plug, so i had the manifold and everything around there off. never even realized they have very similar looking plugs.

thanks again, and if you're even down in DC, i owe you a beer or 6.

You can thank Vinny for that one! Vinny and I PM'd back and forth for days trying to figure his problem out. He finally did a wire trace by color and determined that he had them reversed. I happened to recall that one of his symptoms was a excessively high IAT reading.

[chiefchaka4]

Bringing back an old thread for a second.. which wires are you referring to? I seem to have the same problem and also have had the manifold off but I believe i've done the same thing he did.

[old guy]

Bringing back an old thread for a second.. which wires are you referring to? I seem to have the same problem and also have had the manifold off but I believe i've done the same thing he did.

The wiring harness shown in this pic that is plugged into the IAT (green and white wires) should be plugged into the thermostat heater. The two connectors are reversed.

[Seerlah]

He is saying the two connectors themselves. They look identical for the t-stat and IAT sensor. How they distinguished they were reversed (placed on incorrect sensor) was the colors of the wiring. If you had your t-stat disconnected along with IAT sensor, he is saying it is very probable that they were placed back on to the incorrect sensor. If you never unplugged your t-stat, then your issue differs.

[chiefchaka4]

ah perfect it's exactly what I did.. do you know by chance if this would affect my boost i'm basically running stock boost even though it's tuned to 20psi

[old guy]

ah perfect it's exactly what I did.. do you know by chance if this would affect my boost i'm basically running stock boost even though it's tuned to 20psi

It probably will since the ECM will think the IAT's are excessively high. Be sure to reset your ECM after correcting the wiring harness plugs.

[chiefchaka4]

Exactly what I did..

[old guy]

Glad you got it sorted out

[chiefchaka4]

How do you reset ECM

[old guy]

How do you reset ECM

Do you have any software (VagCom, VCDS) or a Torque App? If not you can force a reset by simply disconnecting the battery, run a jumper between the two disconnected terminal leads to discharge any stored capacitive energy, wait about 15 minutes and then hook the battery back up.

[chiefchaka4]

Sorry I had a brain fart.. I ECM/ECU

[chiefchaka4]

I Have the Torque App and a bluetooth dongle

[old guy]

Sorry I had a brain fart.. I ECM/ECU

I tend to confuse sometimes when i use ECM/ECU (engine control module/Engine control unit) interchangeably. Obviously both are the same thing.

[old guy]

I Have the Torque App and a bluetooth dongle

Perfect. Just click on the Fault Codes icon, go to the menu and click on Clear Faults on ECU. This will reset any DTC codes as well as your readiness codes.

[chiefchaka4]

Perfect yeah I figured that what you meant just mixed myself up.

[chiefchaka4]

Thanks Again Old Guy!