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Alright, these problems are pissing me off

Discussion in 'ECU's, Electronics, and Tuning' started by dohcvtec_accord, Jul 2, 2003.

  1. dohcvtec_accord

    dohcvtec_accord WRX Sellout

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    For quite some time now, my ECU likes to throw code 10 (Intake Air Temp sensor) after the car is warm and when the weather is warmer out (usually above 60 degrees). Let me run down the items and symptoms:

    - As I said, it will only happen when the car has been running for awhile and when it's hot outside. EXCEPTION: On extremely hot days (like today), it'll throw the code as soon as I start the car.
    - When it comes on while driving, I can feel the ECU retard the timing and cut my power.
    - I'm not running hot, and all things in my car are carefully maintained (full oil, full coolant, well-running plugs, distro, timing, etc).
    - I've replaced the IAT sensor with a new one, and that's not the problem.
    - When I swapped my H22, I had a problem making the fans work, so I jumpered the fan switch to make the fans be on all the time (yeah, ghetto, I know).

    OK, so my thoughts are these. I could try getting a cold air intake (currently running a filter on a stick), but I don't think that's the problem, since, as I said, the code will come on as soon as I start the car on REALLY hot days. The reason for that, I think, is the black hood I have is heating up the air under the hood, and causing SOME sensor to get extremely hot.

    My question is: Could having the fans jumpered have something to do with the code? In other words, would the ECU be freaking out about a sensor getting hot WITH the fans being on, and throwing the code?

    I've done almost all the troubleshooting in my Helm's manual, without any luck.

    I've got a few more items to check before I send the car to the wrecker. :) One of these involves getting a pinout for a JDM P13, since I think the JDM and USDM ECU's are different. My reason for this is, my Helm's shows there being TWO Engine Coolant Temperature switches, and my engine came with one. So I need to find where to wire the one ECT switch back to the ECU. Can anyone help me out with that?

    I know this is alot of shit. Any help would be appreciated.
     
  2. ohmstable

    ohmstable Senior Member

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    I know there's a coolant temp "SWITCH" which is a switch used to turn on/off the cooling fan. It's an always open switch which closes when the engine coolant reaches a certain temperature. Then there's a coolant temp "SENSOR" which sends the signal back to the ECU for the temp gauge and perhaps some other engine controls. I don't the the ECU knows when the fans are on or off, the ECT switch takes care of that.

    If I were you, I'd check the IAT sensor resistances again. Make sure it's in spec. If that checks out then I would check the wiring back to the ECU and try and measure the IAT resistances directly at the ECU harness. Just to ensure the wires aren't screwed.

    Temperature Resistance
    oF (oC) (Ohms)
    -4 (-20) .............................. 15,000-18,000
    68 (20) ................................... 1000-4000
    176 (80) .................................... 200-400

    Let me know what you come up with.

    I'm having a similar issue with my JDM H22. Except it keeps throwing the knock sensor code. Only does it when the car warms up and then it retards the timing and the car starts to drive like shit.
     
  3. dohcvtec_accord

    dohcvtec_accord WRX Sellout

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    Yeah, I've been reading up in my Helm's, and it doesn't appear that the "switch" goes to the ECU. I think it goes to the fan relay, which turns the fans on or off. The coolant temp "sensor" actually goes back to the ECU, and runs the temp gauge and maybe some other inputs, like you said.

    I know that my IAT is good, it's brand new. Hell, my old one may have still been good, I'm thinking the problem lies elsewhere. I think I've got to check some wiring, checks some grounds, and see what I come up with.

    The only reason I don't think the wiring is bad, is that like I said, it only throws the code on warm days. This NEVER happens in the winter when the temperature is cold outside. This is what confuses me, and makes me think I may need to go to Honda or someplace to troubleshoot this a little more.
     
  4. rudeludenotmeanthough

    rudeludenotmeanthough Senior Member

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    Check your IAT sensor itself.... i had the smae problem, and it turned out that one of the wires on my IAT sensor had broken off. It could be a bum sensor too.

    Im not sayin its for sure.. but check it out.
     
  5. dohcvtec_accord

    dohcvtec_accord WRX Sellout

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    No, like I said, it's a brand new sensor, bought from Honda. I can't believe that both the old AND new sensors are bad. As I said, I think it's a wiring problem, which is what I'm exploring next. Just hoping that someone on here might have had a different suggestion.
     
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