I've got the F1 light on my 400 LO Burgman. The TPS has been changed to an aftermarket one but it runs perfect. If i swap it back to the original TPS the F1 goes off but the idle is slightly erratic and it will stop after about 2-3 mins of idling. With the cheap one in the idle is fine and it doesn't cut out.
Any ideas folks?

I think you've answered your own question.

The original TPS is broken, the replacement is the wrong part with a resistance outside what the ECU is designed for.

You need one that's working and the right spec.

Andy

It was a combination of c28 and c29 sensor errors.
Secondary throttle sensor was out of spec so i reset it to 0.5v closed butterfly with a meter then checked it with the dealer tool and its spot on, fully open it reads 4.99v.
I then checked the function of the genuine TPS as it didn't run right with it, previous owner spent 100's trying to fix it but failed hence why I've got it now. Hence asking as i had no idea what he had done and what to check, not because i'm thick.
Anyway when I turned the ignition on the valve pre run sweep wasn't working just bouncing the butterfly so something was wrong.
I checked the voltage and position of the TPS again meter and dealer tool and it was in the correct position but not working right, valve didn't do a close open, close sweep ike it should.
I took it off and unplugged the svta motor and opened the butterfly fully, plugged it back in and turned the ignition on and it did the full sweep so that was working but not from closed, it just fluttered it.
Next step was to unplug the svta again, take the TPS off and hold the butterfly open, i then held the TPS at an angle and slid it on to the butterfly rod in the open position and twisted it up to line the green dots up so it put the TPS under pressure. Lightly locked in green to green dot and plugged it all back in. Pre run sweep completed in full, valve shut, open, shut and to start position. Started it up and it ran, no F1 light and C28 and c29 error codes gone but TPS sensor light showed it in the wrong position and soon enough it choked up and stalled.
I looked at the butterfly position and loosened the TPS sensor screw off, tilted it forward and it closed the butterfly, back it opened it so i moved it just passed the green dots and that slightly opened the butterfly, scan tool showed the TPS to be in the correct position but green dots slightly out of line. Fired it up, runs perfect, full throttle, perfect idle, sat and idled without stalling for half an hour with different throttle positions on the main stand. Idles at 1500rpm, revs freely to the red line, no bogging down or hesitation.
All error codes are now off, F1 light is off, all sensors are now in the correct position and the motor sweeps on pre run as it should. Done.
So my conclusion is not to post on here for answers when only one person answers with sarcasm when i can fix it myself in under an hour.

Chris, your last post shows that you most likely know and understand these tech matters better than most of us, so please don't be offended at the lack of helpful replies, people on here do try to help and advise, but only within their own knowledge limits.
Robin.

"C28/C29" is a massively more useful level of information than "FI light on".

After 30 years of fixing vehicle electronic faults my crystal ball is still limited by GIGO.

Andy

I posted the question well before i knew it had a plug in the harness and got a dealer switch to see what was wrong. The issue you get posting questions is everyone assumes you're thick and is 99% of the time sarcastic rather than helpful.
Thank you dogwheel, i didn't know anything about the issues and fixes but figured it out in about an hour of looking and seeing what was wrong then reading how to test it. Problem solved, bike is now ready to go now I've just stripped and rebuilt the rear caliper and parking brake system.
Send me your crystal ball andym, i'm sure i can fix it for you! The TPS was not broken as you suggested just not in the correct position to allow the STVA to do its pre run sweep and needed resetting. 30 years of fault fixing didn't do you much good did it!! Oh by the way i also have had years of electrical fault diagnostics, engine rebuilds and car building, just nothing to do with Burgmans so i was after some guidance.

End the bickering, please.

It's not healthy debate, and it is certainly not helpful on the forum.

It has been years since I had to step in with my moderator's hat on, and I'd really rather not.

capitano wrote: Thu Dec 04, 2025 7:50 am End the bickering, please.

It's not healthy debate, and it is certainly not helpful on the forum.

It has been years since I had to step in with my moderator's hat on, and I'd really rather not.

Agreed. Reading what AndyM wrote does not seem "sarcastic", with the limited information given it is a justifiable factual response. Cromer-chris, your follow up posts are assumptive then increase to sarcastic, give people the benefit of doubt first before you make an ass of yourself.