How to?? Measure TPS Voltage... which wires, etc

[al_roethlisberger]

OK, we'll see what happens here.... the forum blew up when I first posted this topic, but it posted without the first.... well, POST. Very weird.

 

Anyway, basically, here's the jist of what I wrote:

 

 

This last weekend I decided to check my TPS voltage, while balancing the TBs, etc.... just on a lark.

 

The bike ran fine, but since I had never performed this check before myself, I thought it would be good to give it a try.

 

Well, after several tries/methods of probing the purple/black wire on the TPS connnector with the positive lead of my DMM, and grounding the negative lead.... I got nuthin'

 

Now, it could be that my cheapo DMM doesn't read milliVolts too well, but it does have a 2V range that is supposed to .... but I read nothing, and no change when the throttle was moved(with the ignition on, as per Guzziology).

 

So, I would like to ask if someone can take that time to fully explain the procedure for testing the TPS voltage, just to make certain I(or others) don't overlook something in the process.

 

Thanks!

al

[Guest ratchethack]

Al, the TPS voltage is measured between the top and bottom pins on the connector with the key in the "on" position, or bottom pin and ground. I wired up external connectors to make it easier to read when adjusting the idle RPM. Of course it's an iterative process, because when you adjust one, it changes the other. If you're using a cheapo DMM, it should read close to .5v just fine in a 2v range.

[Mr. Bean]

Thanks for posting this question Al.

 

I had the same question myself. My bike is running very well, but I wanted to try and see what the setting was anyway. I never was able to get any response on the multi-meter either.

 

The instructions I was using from Guzziology said to pull back the rubber boot and connect to the purple/black (positive) and blk (negative). My bike does not have a rubber boot that I can see when it is plugged in to the sensor. I tried using a couple very small paperclips to push down along the wire holes but still got no response.

 

Can someone maybe post a picture of what it looks like to hook up a MM to do this test?

 

Thanks,

 

Randy

[Guest ratchethack]

Hey Guys - the TPS connector has to be connected when you take your reading, and again - the key has to be in the ON position to get voltage to it. It's a little difficult to get the standard kind of DMM probes into the connector to do this. You'll have to experiment a bit. At first I was using a pair of 2" long pieces of safety wire carefully pushed into the pins thru the back of the bike side of the connector with needle-nose pliers, and "hooking on" with hook-type probes (Radio Shack). Later on, I replaced the safety wires with a pair of copper bell wires with the insulation stripped back and easily accessible, insulated female spade connectors on the other ends. These work 100% better. I ran the bell wires through the rubber boot and just left them on, zip-tied them in place. I've taken dozens of readings this way, fiddling with the TB balance and idle. It's been tedious to get it all right but in my case it was well worth the effort. Runs better than ever now. I'm currently running 515mv at the TPS. If you really want I can try posting a shot with my new Cannon A80, but whether or not it'll work is gonna be a gamble LMK.

[callison]

http://home.pacbell.net/guzzi007/tps/TPS.html

[Guest jonny c]

The best way to back probe is to buy a package of "T" head sewing needles. they are about 1" long can be bent and provide a great connection for the DVM's (digital volt meter) alligator clips!! We have been using these for automobiles for years

[Guest Bruce]

You can also check it where it goes into the 'computer' under the seat. I carefully shaved off a bit of insulation on each wire. There are in-line test ports which are suppose to be easy to install which would be an improvement. IMHO this is a critical reference point for your system.

 

A bit off topic, replacing those star drive screws on the TPS with good old allens will make the adjustment task much easier.

[Mr. Bean]

Thanks all

 

Now if I can get a spare few minutes I'll try these ideas.

 

Randy

[Guest dogbarczar]

I have a 2003 V11 Sport and checked my Throttle position sensor output value with a T needle stuck in the top wire, my reading at idle was 0.5 to 0.7 mV. This is quite different than the 500 mV specified. Do the newer fuel injection systems use lower values? Does anyone have a shop manual which specifies the amount?

 

The bike must be running to get a reading as the computer supplies the needed voltage to run the Throttle position sensor. I am an electronics tech and do know how to use a DVM and double checked the readings. When reving the engine to about 2500 rpm, the reading also goes up to about 2.8 mV.

[big J]

Readings should be taken from the top and bottom pins on the TPS and should be read with the ignition switched on and the kill switch in the "run" position. With the cold start mechanism disconnected from the right hand throttle body, and the connecting bar removed it should read 140mV. Reconnect cold start and bar, it should read 375mV for a stock set up or 525mV if you've got a Power Commander, adjusted by the 2.5mm grub screw on the left throttle body. This is a highly truncated version, check the "setting TPS, synchronising, etc" info in the forum. These settings are of course optimum factory type settings, in realitythey can be all over the place. Is the bike running ok? If it is,dont mess with it, get down on your knees and thank the Luigi that built it that you got a good one.

[Guest ratchethack]

I have a 2003 V11 Sport and checked my Throttle position sensor output value with a T needle stuck in the top wire, my reading at idle was 0.5 to 0.7 mV.  This is quite different than the 500 mV specified. Do the newer fuel injection systems use lower values? Does anyone have a shop manual which specifies the amount? 

 

The bike must be running to get a reading as the computer supplies the needed voltage to run the Throttle position sensor.  I am an electronics tech and do know how to use a DVM and double checked the readings. When reving the engine to about 2500 rpm, the reading also goes up to about 2.8 mV.

55253[/snapback]

Dogbarczar, I hesitate to question the read of a Pro Electronics Tech here, but something is out of whack. Best re-check things - sure you got the DVM on the right scale? Your bike wouldn't have enough voltage at the injectors at 0.5 to 0.7, or even 2.8 mV to run at all. Now 0.5 to 0.7 V, however, should make it run properly if fitted with a PCIII, but you'd be running rich up closer to 0.7 V. As stated above, 500-525 mV (TBs connected at a ~1100 RPM idle setting) is what the Dynojet Guzzi Guru spec's for PCIII-equipped bikes. It's not necessary to have it running to check the TPS voltage, but the ignition has to be in the run position as mentioned. TPS voltage reading is entirely independent of engine RPM and increases directly with the opening of the butterflies in the TBs.

[dlaing]

I traced the two required wires back towards the ECU and spliced and soldered in a pair of wires with female spade connectors:

I keep them wrapped with electrical tape(not shown) to reduce the chance of them shorting or drowning in water.

[Guest dogbarczar]

I connected two T needles to the top and bottom wire of the TPS sensor and now am getting the right values, around 425 mV. Thanks!

[tomsp]

Al, I did this and it seemed easy enough -- disconnect the TPS connector plug thingy, right at the TPS. Insert tiny wire leads into the two holes in question and re-connect. Run the two tiny leads newly coming out of the re-connected TPS connector, to your mv reader and you got a good read. The tiny leads yo insert must be small enough to ensure that the connector can indeed by re-connected with positive effect!

 

[quazi-moto]

I used a pair of pins that I took from a new shirt that I had received as a gift. Some call me thrifty. That's polite talk which really means that I'm just plain cheap. Anyway I was able to get my voltage readings this way when I replaced the stock TPS sensor with the Harley version. I set it for 150mv with the throttle plate closed and then adjusted the throttle stop screw until I was reading around 510mv. Hopefully this is the correct procedure because these values (I believe) are for a stock TPS sensor. After I obtained the 510mv reading I balanced the TB's with a Twinmax unit (nice) by adjusting the left hand stop screw. Then I cracked open the airbleeds (1/2 turn) and doublechecked for balance. A minor tweak on the left hand air bleed had the Twinmax right on zero. I had to adjust the linkage bar before re-connecting it or it would have pulled the right throttle plate off the stop screw. After doublechecking for cylinder balance I also checked the TPS sensor voltage to make sure nothing had moved. All was well so I embarked upon a little shakedown run. The bike felt smoother and seemed to be running a tad richer off idle, but it still leans out and surges a little in the midrange. This is now confined to around 3500-4000 RPM so overall running has been improved, but not quite perfecto! I have the PCIII mounted on this '02 LeMans along with FBF intake, Stucci X-over and Staintunes. I had read that the 1.5M ECU has a fuel trim screw under the little bung plug thing, but I didn't notice it when I removed the plug so I just popped the plug back in and let it be. There's an approved tuning center not far from where I live so my next stop is the dyno shop to get the injection map sorted out.