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Loosing 5v reference signal to map and tps, cycle key a few times fixes

  • Suselman92
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14 Mar 2020 09:32 #38333 by Suselman92
I have an 03 accord 2.4 coupe that recently started having some issues, at first it threw a code for tps and map so naturally instead of investigating I just put new parts on it, then after awhile the problem started getting worse, here’s what the car does ONLY after sitting more than 4 hours. You start the car and within 5 seconds it dies and looses 5v to the map and tps maybe more but the map and tps is all I’ve checked. Weird thing is when it is acting up and dies the left turn signal comes on briefly. You cycle the key 2-4 times and the car will run great for the rest of the day, any input would be appreciated as I don’t know where to start now

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14 Mar 2020 10:10 #38335 by Suselman92
I forgot to mention I also have a code for a bad rear 02 sensor, I was really thinking the map or tps was grounding out

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14 Mar 2020 11:15 #38340 by John Curtis
What are the weather conditions when this is happening? Is it really cold/hot?

Due to when it’s acting up, I would suspect a sensor shorting out pulling down the ref voltage. Unplugging sensors is the way to go here. Does the voltage slowly climb back up or jump to 5 instantly?

Thinking out loud always helps me in the process.

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14 Mar 2020 12:54 #38344 by Suselman92
It’s pretty chilly, 30-50 degree mornings, 5v will instantly come back, on first start after sitting I’ll have the 5v for about 3-5 seconds then drops to nothing, start it 2-3 times and it’ll come back. The thing that really throws me off if the left turn signal lighting up whenever it messes up.
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14 Mar 2020 14:16 #38349 by John Curtis
If the unplug it test isn’t fruitful, you may be having a power problem (think relay failing). I pulled a diagram on my laptop saved ready to upload here whenever I finish up here at this dealership but got a couple other cars to deal with. In the meantime, when it acts up and stalls don’t touch the key and just leave the key in the same position you try tapping on the relay that powers the PCM. If you don’t get 5v ref back use a test light at the relay and see if you have what you need there to make the relay work.

Do you have a scan tool that can read enhanced data? Does it become a no com, when it stalls out? (I would assume it’s a no com) Monitor the ignition switch if possible. I’ll be able to help better once I can dig in and upload the diagram (seems like a fairly simple circuit)

Thinking out loud always helps me in the process.
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14 Mar 2020 14:22 #38350 by jreardon
My theory is maybe it's a bad contact in the ignition switch after reading that you fix it by cycling the key over and over.

While the 5V is missing (critical), key on, can you do some checks like see if the Windshield Wiper Motor works and if Fuse 19 remains hot at key on?

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14 Mar 2020 15:05 #38352 by Suselman92
If I don’t shut it off it will never regain 5v, one thing I have noticed is that it makes a odd noise near the relays when it messes up, almost like a whine and will come and go with the turn signal. My scan tool continues providing data during the outage so I didn’t figure it was the relay to the pcm.

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14 Mar 2020 15:09 #38353 by Suselman92
Everything continues to work during the outage, it’ll light up left turn signal for a second and other than that it’s the only thing that changes, I don’t really think it’s in the ignition, I still have power to everything else, fuel pump runs, wipers work, turn signals, everything that isn’t powered at key off works

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14 Mar 2020 16:18 #38357 by Cheryl
Can you get to the pcm and locate the 5 volt reference wire and next time it acts up just cut the wire where you can fix it easy. If it restores the 5 volts issue is under hood sensor or wiring if it doesn’t you can eliminate all of that in one test

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14 Mar 2020 18:27 #38360 by Suselman92
I’m not sure which wire goes to map/tps or I would

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14 Mar 2020 18:29 #38361 by Cheryl
There’s got to be more than the map and tps on the reference wire. I think another member posted the wiring diagram

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14 Mar 2020 18:56 #38362 by Suselman92
Ok I have an update, right before the car starts running bad on startup I hear a relay by the hood release click

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15 Mar 2020 10:58 #38377 by derekoliveira
Turn signal must has something in common with ECM, and it can be + or -!?

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15 Mar 2020 15:47 - 15 Mar 2020 16:02 #38386 by jreardon

Suselman92 wrote: I’m not sure which wire goes to map/tps or I would


Here's wiring diagram

File Attachment:

File Name: 2003HondaA...d2.4.pdf
File Size:315 KB


Exterior lamps:

File Attachment:

File Name: extlamps.pdf
File Size:190 KB
Attachments:
Last edit: 15 Mar 2020 16:02 by jreardon.

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15 Mar 2020 17:27 - 15 Mar 2020 17:29 #38389 by Monde

Suselman92 wrote: I have an 03 accord 2.4 coupe that recently started having some issues, at first it threw a code for tps and map so naturally instead of investigating I just put new parts on it, then after awhile the problem started getting worse, here’s what the car does ONLY after sitting more than 4 hours. You start the car and within 5 seconds it dies and looses 5v to the map and tps maybe more but the map and tps is all I’ve checked. Weird thing is when it is acting up and dies the left turn signal comes on briefly. You cycle the key 2-4 times and the car will run great for the rest of the day, any input would be appreciated as I don’t know where to start now


Are you losing 5v reference to only the MAP and TPS sensors when the car dies or to other sensors as well? If you lose the 5v reference to other sensors as well, I would also monitor power and ground to the pcm to see if I lose them before I lose the 5v ref.

Never assume, diagnose!
Last edit: 15 Mar 2020 17:29 by Monde.

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16 Mar 2020 10:18 #38403 by Suselman92
I would assume I’m loosing 5v to other sensors as well, changed pcm relay, srill does same thing, car starts, idles for a few seconds, relay clicks and car dies, when I say car dies it doesn’t die from lack of fuel or spark, it will stay running if I give it gas, it just dies from loosing tps signal. Honestly the car will probably end up going to the junkyard in a few days

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16 Mar 2020 11:49 #38404 by Suselman92
If it was in fact the ignition switch wouldn’t it not run at all? The thing that really stumps me is that the car never did this prior to the throttle body replacement, it shifted bad,idled high and the shift interlock release wouldn’t work, but it never ran bad or lost 5v

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