joelmatt89

i tried searching but the search sucks so bad so i guess i will just start a thread. I was just checking my tps and the voltage was all good, it had constant 5v at the one wire and .53v on the other with it closed and a smooth transition up to 4.63v with it open all the way. I thought the other wire which is green/white was a ground but i messed around with it for a while and couldn't get any continuity to any grounds. Can someone help me on this one

joelmatt89

common someone has to know the answer to this. I was just messing with it again and sometimes i can get like 40 ohms of resistance between that prong and the battery ground. If someone could test theirs or something really quick i would really appreciate it.

newtron63h

should be ground. 3 wires............one is the signal(usually .5V-4.5V), one should have about 5V constant, the other should be ground.

joelmatt89

okay thanks i appreciate that i ll have to mess with that wire, someone on another forum told me it grounds to the ecu is that true, that doesnt really make sense to me

Jimster480

yes it is a ground, you wont get a reading from it.

newtron63h

im not sure where exactly it will ground to, but it should definitely be a ground and you should always be able to get continuity to ground on that wire.

Former User

Yes, the Grn/Blk wire grounds to the ECU. I think it is activated to ground only with the key turned to ON(II).

Here's the relevant test: Turn the key OFF. Disconnect the TPS connector and then turn the key to ON(II). From the wire harness connector, you should measure ~5V between terminal 1 (ground) and terminal 3 (reference voltage). If so, the Grn/Blk ground wire is fine.

honda.lioness

This is because there is a physical and electrical difference between chassis ground and the various sensors' grounds. When the ignition key is in ON (II) --
--the green/white TPS wire goes to a special ground in the ECU called "sensor ground." This is different from the Honda chassis ground.
--the potential difference between "sensor ground" and the Honda chassis is around 10 mV.
--you will not get continuity between the green/white wire and chassis ground.
--most or all of the emissions control sensor ground wires are not electrically continuous with chassis ground.

For the Civic, the ECU's main ground (I think a.k.a. "power ground") is grounded to the chassis (and so battery negative) via the thermostat housing. Sensor ground is electrically separated from the ECU main ground by a resistor (internal to the ECU?) of about 30 ohms. With the key in ON (II), these sensor grounds all connect to the ECU main ground via the resistor.

The purpose of having a sensor ground (one that is separated from the main ground by a resistor) is to preclude the various sensors' voltage signals from being affected by variations in voltage at the main ground caused by varying current flowing from other larger, electrical components (ones that use serious power compared to the various engine sensors) grounding to the chassis. The sensor ground exhibits less noise than the main ground.

"Sensor ground" also seems to be synonymous with "signal ground" and "clean ground." Though I guess "sensor ground" is not perfectly clean but rather is a lot cleaner than if the resistor were not there.

I see with the ignition key off or removed, the sensor ground is electrically continuous with chassis ground.