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IAT Modification Problem
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sixmenn Offline
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Post: #1
IAT Modification Problem
Recently I placed a 10K resistor in parallel with my IAT sensor. After a couple of days my CEL came on. When I check the code it is #24, which is the IAT sensor, so I removed the 10K resistor, but the CEL will not go off.

I have removed the fuse that my manual indicates will reset the CEL. The CEL still comes on. I have even disconnected the battery for a couple of hours, but after reconnecting and starting, I still have the code.

I have double checked the wiring, and there is no apparent short. The places in the wire that I stripped so I could solder in the 10K resistor are taped up so that they do not touch one another.

I have also checked the resistance across the sensor itself to ensure that the sensor wasn't damaged somehow. It appears to be acting normally, and even changes readings when I breathe warm air on it.

Anyone have any ideas what could be causing the IAT to deliver this code, or an alternative to get it to reset? Is it possible that the EFIE I installed could be contributing to this code?

HELP!!

1994 Camry 2.2L 4 cylinder
Smacks Booster
ZFF EFIE with 50 millivolt offset (still tuning)
IAT parallel 10K resistor
CTS parallel 3.9K resistor (removed for winter)
MAP sensor enhancer
Fuel pre-heater
(This post was last modified: 09-29-2008 06:15 PM by sixmenn.)
09-29-2008 06:15 PM
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colchiro Offline
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Post: #2
RE: IAT Modification Problem
Here's some info on Toyota codes (from my Toyota Sensors link) and how to clear them: http://www.troublecodes.net/Toyota/

Did you disconnect your wiring anywhere?

Here's some help troubleshooting IAT sensors: http://www.autoshop101.com/forms/h32.pdf

Rick

Links: Documents / Tuning for Mileage | Toyota Sensors | Autoshop Sensor Tutorials
09-29-2008 06:41 PM
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dr_dx Offline
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Post: #3
RE: IAT Modification Problem
sixmenn Wrote:Recently I placed a 10K resistor in parallel with my IAT sensor. After a couple of days my CEL came on. When I check the code it is #24, which is the IAT sensor, so I removed the 10K resistor, but the CEL will not go off.

I have removed the fuse that my manual indicates will reset the CEL. The CEL still comes on. I have even disconnected the battery for a couple of hours, but after reconnecting and starting, I still have the code.

I have double checked the wiring, and there is no apparent short. The places in the wire that I stripped so I could solder in the 10K resistor are taped up so that they do not touch one another.

I have also checked the resistance across the sensor itself to ensure that the sensor wasn't damaged somehow. It appears to be acting normally, and even changes readings when I breathe warm air on it.

Anyone have any ideas what could be causing the IAT to deliver this code, or an alternative to get it to reset? Is it possible that the EFIE I installed could be contributing to this code?

HELP!!

Make sure one side of the IAT goes to ground. Check with an ohm meter.
10-09-2008 03:06 PM
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visek Offline
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Post: #4
RE: IAT Modification Problem
sixmenn Wrote:Anyone have any ideas what could be causing the IAT to deliver this code, or an alternative to get it to reset? Is it possible that the EFIE I installed could be contributing to this code? HELP!!

10K probably makes the ECU think your IAT is not functioning....stuck at "engine cold"?

http://www.fuel-saver.org/showthread.php?tid=1658

As far as I know...coolant temp sensors and air intake sensors are thermistors and operate in much the same way. If you are DIY...you want to use a pot in order to be able to adjust your settings?

Check out the CHT setup here?

http://www.nonags.org/members/nijqk/Sens...0_Z24i.doc
(This post was last modified: 10-10-2008 12:52 AM by visek.)
10-10-2008 12:44 AM
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01olds Offline
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Post: #5
RE: IAT Modification Problem
HI just a note..i am using a small volume controll resisit to controll this car (I A T) its set at 90 temp something like 2.22 volts i think so far seems to work ok...it just time consuming but fun too. ... oh just a tid bit of personal observiation this car check engine stays on all the time .actually theres is no problem ! i have drove it some 70000 miles every where. runs perfect...so yes we know all cars are different i put some black tape over the light so i didnt have to see it all the time...some trick huh... but it still runing just fine.. good luck ... don.
(This post was last modified: 10-10-2008 06:48 AM by 01olds.)
10-10-2008 06:02 AM
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visek Offline
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Post: #6
RE: IAT Modification Problem
01olds Wrote:HI just a note..i am using a small volume controll resisit to controll this car (I A T) its set at 90 temp something like 2.22 volts i think so far seems to work ok...it just time consuming but fun too. ... oh just a tid bit of personal observiation this car check engine stays on all the time .actually theres is no problem ! i have drove it some 70000 miles every where. runs perfect...so yes we know all cars are different i put some black tape over the light so i didnt have to see it all the time...some trick huh... but it still runing just fine.. good luck ... don.

Unless you are monitoring the O2 for cycling either using a multimeter or scangauge...you could be running in open loop....running good but using more gas?
10-11-2008 02:19 AM
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01olds Offline
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Post: #7
RE: IAT Modification Problem
visek Wrote:
01olds Wrote:HI just a note..i am using a small volume controll resisit to controll this car (I A T) its set at 90 temp something like 2.22 volts i think so far seems to work ok...it just time consuming but fun too. ... oh just a tid bit of personal observiation this car check engine stays on all the time .actually theres is no problem ! i have drove it some 70000 miles every where. runs perfect...so yes we know all cars are different i put some black tape over the light so i didnt have to see it all the time...some trick huh... but it still runing just fine.. good luck ... don.

Unless you are monitoring the O2 for cycling either using a multimeter or scangauge...you could be running in open loop....running good but using more gas?
is running in cloosed loop well that mod as welll as outhers of course.....something like just over 40 m p g tunning for millage was a big help.....
10-11-2008 02:41 AM
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Atfab Offline
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Post: #8
RE: IAT Modification Problem
sixmenn

Did you ever figure out what was wrong?

Atfab
99 S-10 Pickup 2.2L auto, Std cab, Short bed, Alum cap
Stock, Ave. 25.5 MPH
10-28-2008 12:51 PM
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01olds Offline
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Post: #9
RE: IAT Modification Problem
.......HI to you also Rick & rest of the folks oh thing are improving m p g increasing..with just the lean outs only so at this post i am verry incouraged so as the car computer re learns ..it in theory be ok....... see ya all later good luck Don.
10-28-2008 01:32 PM
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sixmenn Offline
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Post: #10
RE: IAT Modification Problem
Yes. I had a bad crimp connection in my EFIE hookup. How in the world that ever caused an IAT code I'll never know, but when i fiddled with the wiring, the CEL went on and off. After fixing the connection, no more CEL.

Still not seeing any mileage gains, though. I'm thinking of removing all modifications and starting over....

Atfab Wrote:sixmenn

Did you ever figure out what was wrong?

1994 Camry 2.2L 4 cylinder
Smacks Booster
ZFF EFIE with 50 millivolt offset (still tuning)
IAT parallel 10K resistor
CTS parallel 3.9K resistor (removed for winter)
MAP sensor enhancer
Fuel pre-heater
11-03-2008 04:04 AM
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