TPS signal erratic - possible grounding issue?

[drew6]

Hey guys,

So I just installed a MS3X on an RB26. I have it all wired up as per the manual and all connections are very secure. I just loaded the firmware on to the unit and started doing the first sensor calibrations when I noticed my TPS was all over the place. Upon further investigation I realized that the tps was actually fluctuating with the electrical load on the car (IE: when the dome light or brake lights were turned on the TPS signal would start jumping around).

Appreciate any input. This is my first megasquirt install.

[Pat kelly]

I am new myself to Megasquirt and probably the last person to take advice from. the tps is a 5v feed back from the ms3. have you any 12v supply to it thru the loom by any chance, are you running new wires to the tps itself. if you have new wires that dont connect to anything else you should have no interference from any other supply, are the wires near the coils/alt, they could interfere. check the tps with a multimeter, it should be a steady rise fall for resistance. when you turn it, could you borrow another just in case yours is faulty.

my 2 cent.

Pat.

[jsmcortina]

As you are using RB26, please see:
http://www.msextra.com/forums/viewtopic ... 25&t=55156

James

[drew6]

Pat and James thanks for the input. I just updated the MS3 with the new firmware but there is no change.

Here's what I found out so far:

- The TPS was only getting .5-.6V not 5v. I then tested my MS3 on the stim and it showed it was putting out ~4.93V. I figured it must be a problem in my connections so I cut apart my nice new loom and manged access the the wires. I then realized that when I cut the VREF wire down stream of the TPS the ~5V returned to the TPS (The CAS uses 2 pull up resistors from the VREFhttp://www.diyautotune.com/tech_article ... b25det.htm). When I hooked up the "downstream" VREF wire to the TPS again the volts dropped to ~.5-.6. (Also, the fuel pump kicks on for a couple seconds when you discount the wire - ?)

- When I have the V ref wire going directly to the TPS it shows a voltage of 4.95V. When the dome light is on it goes to 4.96. When the brake lights are turned on it goes to 5.01. Is this normal? Should it be fluctuating at all?

Any help at all is greatly appreciated.


EDIT: I fixed the voltage fluctuations, in regards to the lights, by cleaning up all the body grounds. However, my VREF voltage problem is much more complex and I have started a new thread.