TPS wiring and ecu grounds

s300 and SManager software questions & answers
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2x0
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TPS wiring and ecu grounds

Post by 2x0 » Sat Mar 10, 2018 8:55 am

On my p28 when I started the car for the first time this year, it was getting no TPS signal. I checked the wire and someone had spliced another wire into the TPS one, which I somehow accidentally ran to ground because I thought that’s where it went before. Probably my mistake.

I cut that wire and TPS reads fine now, but after driving I started having some other weird issues such as fluctuating AFR, my fan relay clicking sporadically etc making me think I have a bad ground.

Question is, why the hell would anyone have spliced a wire into the TPS to begin with? Is there any purpose for this?

Second, I checked where the main grounds and logic ground wire ecu pins are, and all of them run into the main harness. Any idea where these actually ground out to so I can check those connections? Can I simply wire them directly to a ground on the chassis?
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

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Hondata
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Re: TPS wiring and ecu grounds

Post by Hondata » Sat Mar 10, 2018 8:29 pm

The logic grounds go into the ECU to an internal ground plane, and then eventually into the main harness which grounds on the thermostat housing. It is always a good idea to check the thermostat ground is clean and tight, and also check the same for the transmission ground strap and valve cover ground wire.
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2x0
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Re: TPS wiring and ecu grounds

Post by 2x0 » Sun Mar 11, 2018 11:19 am

Perfect, thanks! I will check the thermostat housing ground.

Still baffled as to why there was a wire spliced to the TPS signal.
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

forevertrj
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Re: TPS wiring and ecu grounds

Post by forevertrj » Sun Mar 11, 2018 11:38 pm

someone thought! it's an easy fix just temp splice it into this plug here so she can run!
Let's not make assumptions, please leave as much detail as possible!

Evanowens
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Re: TPS wiring and ecu grounds

Post by Evanowens » Mon Mar 12, 2018 3:56 am

The tps shares ground with ECT and IAT sensors, if there is an issue with the ground splice, sensors will read out of spec. People will ground the sensor to "fix" voltage readings, but since it's not getting back via logic ground, they continue to read incorrectly.

2x0
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Re: TPS wiring and ecu grounds

Post by 2x0 » Mon Mar 12, 2018 6:01 am

Yeah, that is my concern now as I delve deeper into the wiring that was done on this car. Wondering what other sensor readings might be off now or what issues I might find.

For example I have my fan control grounding through A12 now and the other day, the relay started "fluttering". Frustrating stuff.

Thanks!
'91 CRX, B18c1, T3/T4, 17psi on e85, FIC 1000cc's, S300 V3 P28

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