Troubleshooting Recently Lost TPS Signal (Inside The Case)

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Troubleshooting Recently Lost TPS Signal (Inside The Case)

Postby Tjabo » Fri Nov 10, 2017 2:20 pm

This is for a home-built MS3+MS3X on a V3.0 board that was running full-sequential fuel, spark and IAC on a '97 BMW 540i with an M62b44 engine, very nicely for several days until the following occurred.

Long story short: I was driving home from the drag strip two nights ago, when I started to roll into boost on the entrance ramp to the freeway. It felt like I hit a boost cut -- way earlier than should have been possible -- but then the engine just would not come back to life. I coasted to the shoulder and the engine would crank like mad, but would not restart. My laptop had died at the track, so I couldn't troubleshoot on site.

After 20 minutes or so I randomly cranked the engine, and it started so I drove the 95 miles home. Last night I went out for a drive to try and replicate the problem, and the only thing I found to be wrong was no TPS signal showing up in TunerStudio, I could not replicate the problem. Today I started chasing the lack of TPS, and found that I have proper TPS voltage from the throttle body all the way to the main connector pin22.

Looking inside the case, I see no problems on the solder joints from the connector to the main board, R9, C9, or C8... At this point I kind of don't know what to check next. Any assistance would be appreciated! :D

I'm not sure they can really help with this, but an .MSQ link is:
https://drive.google.com/open?id=1h_WvG ... pXyMkte-SJ

and here's a log from last night that shows the constant zero TPS:
https://drive.google.com/open?id=1ulRc5 ... fn9EesBRM0

Thanks,

Thad
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby Tjabo » Fri Nov 10, 2017 2:37 pm

Using my JimStim, I see 0 volts on the right side of C8 and C9. On the left side of C8, C9, and on both sides of R9, the voltage ranges from 0-5V with the turn of the TPS knob.
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby Tjabo » Fri Nov 10, 2017 3:35 pm

Eeeewwww, I think this might be a bad/expensive sign. I just popped my old MS2 daughterboard into the V3.0 board and setup a new project for it. TPS works perfectly on that chip. I have a bad feeling something might have gone bad with my MS3 chip... :(
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby DaveEFI » Sat Nov 11, 2017 2:51 am

I'd first try re-loading the code. Could be a voltage spike or whatever has corrupted something.
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby Tjabo » Sat Nov 11, 2017 6:56 am

Thanks Dave, I will give it a try and report back! :)
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby Tjabo » Sat Nov 11, 2017 7:35 am

I think it worked Dave, thank you!! The first reload with maintaining the sensor calibrations and .MSQ didn't work, but then I reloaded again without maintaining anything, et voila! :yeah!:
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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Re: Troubleshooting Recently Lost TPS Signal (Inside The Cas

Postby Tjabo » Sat Nov 11, 2017 8:14 am

Ok, MegaSquirting has always caused me a fair bit of embarrassment, and this is no exception. The actual problem that caused me to loose throttle was nothing more than me goofing around with the DBW settings to see what is in there at the request of the guys on the bimmerforums with M62b44TUs. I forgot to set the mode back from "DBW" to "OFF." :oops:

While it is great to have found the answer to that problem, it leaves me with no idea what caused the car to konk out the other night on the way home from the drag strip... At any rate, thanks to all who looked at this thread, and thanks to Dave for telling me to reflash the firmware, since that is what ultimately caused me to find the problem in my .MSQ. I'm such a dope!! :lol:
--'97 BMW 540i/6spd -- Single Front/Top Mount Turbo -- MS3+MS3X V3.0 Full Sequential
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