20 seconds after starting the little red engine light comes on. Revving the engine just a bit makes the light turn off but it always comes back about 20 seconds later. I have the ThunderMax EFI Tuner installed so I hook it up and under Diagnostic codes it shows a "TPS Low" fault for current and historic that clears current when I blip the throttle. Everything seems fine otherwise so I'm guessing a bad connection somewhere? Where should I start?

 

dis and reconnecting plugs will often brighten a poor connection- for most of the engine control systems we are talking about less than 5 volts and low current, so a little corrosion can have a big effect.

I will often use deoxit, cramolin or blue shower contact cleaners on plugs, I also use a fiberglass pen to clean contacts (nic sand), pins and sockets.

so i would pull the maxi fuse and go through the connections between the ecm and the TPS- incl the thundermax connection and the servo plug on the throttle body...clean up every connection you can.

the tps has 2 potentiometers which are wired so that at full throttle 1 pot will allow 5 volts through- the other zero. at idle this is reversed...and at 1/2 throttle... each will allow 2.5 volts

it is a fail-safe type setup so that the ecm always expects to see 5 volts total and can calculate the TP

or you can ignore it if all this does is flash a light once in a while and you know what it is

mike

 

Thanks Mike! Makes sense. I'll do that and post back this week.

 

Not sure about your year bike. But on pre-Rushmore touring bikes, the connector to the TPS behind the left side of the air cleaner is a weak spot. It is not sealed and pins can get corroded. Mine failed hard during a trip. A dealer replaced the pins, then when I got home I added contact lube, and covered with shrink tube.

 

that is the throttle body servo motor- which reacts to the ecm's commands- if he is showing a TPS voltage error the servo motor may not react "correctly" as the ecm's commands are based on wrong input data.

the sensors gather data and input it to the ECM ( TPS, O2, bario or temp sensors)
The accuators react to commands for the ECM, (that would include injectors, throttle, spark timing)

dielectric grease is a double edged sword- it can reduce corrosion by keeping moisture out OR it can trap moisture in and against connectors.

Mike