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IACV wiring problems. CEL P1508

 
Old 01-26-2016, 10:38 PM
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Default IACV wiring problems. CEL P1508

I have a 97 accord with a f20b engine and a h22 intake manifold. runs and everything but i have a CEL for "IACV circuit failure". the exact code is p1508. I am running a manual p13 ecu.
anyway, I have the wiring for the IACV wired straight to the ecu to pin A12. it is a 2 wire IACV, I have the 2 wires spliced into one that goes to A12, because from all the research ive done the 2 wire IACV only uses that one pin.

Ive done all the basic troubleshooting like cleaning the IACV and checking all the various air hoses. Ive even replaced the iacv and the 2 wire plug and doubled checked all the coolant lines going to it to be correct. the CEL is still there, obviously. So my only conclussions are that the 96 prelude P13 ECU came with a 3 wire IACV or one of the wires needs to be grounded, but from what ive read the 2 wire iacv gets grounded in the ECU and I have found no information that says for it to be wired to more then just A12. Also maybe i just need to drive the car more as the ECU has not seen many miles, but driving it around poses a threat since my tags are backed to 2014 (cars been sitting with various problems and ive fixed them all but this one check engine light)

Can anyone shed some light on a solution of any sort? When i reset the ECU the CEL will stay off for about a minute or 2 and then comes back. The idle isnt even bad once the car warms up and I can even adust the idle with the IACV by turning that set screw sort of deal that is used to adjust it.
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Old 01-26-2016, 11:42 PM
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Default Re: IACV wiring problems. CEL P1508

Im wondering why you think its able to work with only one wire lol. electrical circuits always need a power and a ground to function.

which p13 are you using? the obd1 or obd2a?

to properly/partially answer your question; the yellow/black wire should be spliced into a battery voltage source, typically the main relay ignition output, but you can tap into the coil positive.
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Old 01-26-2016, 11:56 PM
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Default Re: IACV wiring problems. CEL P1508

Yeah I addressed that in various ways in my post if you read the whole thing.. And its not really just one wire by itself since theyre spliced together since the only info i could get is that it wires straight to A12 only. never saw anything that mention a seperate ground.

I am using the obd2 one.

Are you sure I can just ground it to something that gives constant power? I know you do that for the 3 wire, but read somewhere that the 2 wire gets grounded in the ECU and the ecu sort of pulses the electricy in the ground to open and close the IACV.

Honda IACV explained - Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com

That is were i got that info.

Thank you.
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Old 01-27-2016, 12:02 AM
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Default Re: IACV wiring problems. CEL P1508

Only reason i havnt grounded it to something already is because i didnt want to risk frying something. Which is why im here to see if any else has delt with this.
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Old 01-28-2016, 10:33 PM
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Default Re: IACV wiring problems. CEL P1508

I fixed it. I wired one wire how that guy above said and kept one on the ecu A12 pin. I put 2 and 2 together and realized A12 is the ground and sensor and then you source the power from a battery voltage source.
Started up with a extremely high idle, but once it warmed up the idle is fine and the whole car runs better now and the CEL is gone.

Only posting this update so if anyone else has this problem they may see this.
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Old 01-29-2016, 07:32 AM
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Default Re: IACV wiring problems. CEL P1508

Nice
just make sure the power source is ignition voltage and not battery voltage. meaning it should only have power (12v) when the key is on. it should not have power when the key is removed (aka battery voltage)
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Old 01-29-2016, 10:51 AM
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Default Re: IACV wiring problems. CEL P1508

Yes I have it wired to the old external coil that is just looping power since I had to do the convert to internal coil dizzy from external during the f20b swap.
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Old 04-10-2019, 02:11 PM
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Default Re: IACV wiring problems. CEL P1508

:help I have the same problem could you explain more in detail what you did to fix the problem?
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