85 code on initial start only

[Captain Proton]

The last couple of fires on my Ariel Atom 2, the rpm sticks @2500 rpm or so with pops and bangs.  After shutting the engine down, I restart is and it behaves normally, no issues while driving.  I pulled the code which is reads "85 - APS(Main) signal has been less then the specified “Error Low” fault condition for this channel for a continuous period of a more than 2 seconds."  The ECU has been in the car for about 3 years fault free with about 5000 miles on the car.  
 

I pulled the accelerator position plug @ the accelerator pedal and checked the plug but couldn't find anything glaring.  I'm kinda stumped because this ONLY happens on initial start after the engine cools down, about an hour or so.  I doesn't happen when I shut the engine down and start it up within 30 minutes of the shut down.    

[Adamw]

The 2500rpm with pops and bangs is the throttle system going into safety mode, if it thinks there is a safety issue it shuts off power to the E-throttle (the spring will slightly open it to about 7% throttle) and a rev limit of 1800rpm is activated.  

Can you attach the tune and a short log of some pedal presses before cranking, then capture a crank/start up as well.  It would be nice to capture the fault happening in a log if you can but otherwise just a log of a start up may be enough to see if it is getting close to the error triggers.

[Captain Proton]

I'll get it done, attach and report back.  TIA

[Captain Proton]

FWIW< I was wrong on my blink count.  When I plugged in the laptop to the ECU, I found the code; it's 76, not 85.  As I noted above, it has only happened on start up.  Once I turn off the ignition and re-start, the throttle behaves fine.  Here's the file.  

85-code-log.llg

[Adamw]

In that log the error code was already present and the throttle was already disabled before the engine cranked.  

It looks like possibly one of the TP sensors is failing as at the beginning of the log there is a 4.3% difference between TP sub and main, but it is slowly changing untill at the end of the log, only 30 seconds later there is only a 1.9% difference.  Anything over 2% will trip the fault.  I guess it could potentially be a bad connection also.  The 5V supply looks ok.  

 

[Captain Proton]

So, looks like a new throttle body for me then.  Unfortunately, the Ecotec engine uses a throttle body with an integrated TPS so I can't just replace the sensor.  I'll pull of the throttle body, check it out and report back my findings.  Thanks for the assist.

[Captain Proton]

Update; the throttle body is fine and now so is the engine.  After a bit of research on the 1st gen Ecotec engine, I found that the TPS that's integrated into the throttle body is very sensitive to throttle plate angle. The inner wall of the throttle body had a fair amount of soot/carbon/oil buildup that must have not allowed the throttle plate to set to 0° when the engine was stopped which is why I believe the main and sub signals were off by over 2% before cranking.  Once it went into safe mode and I pressed the throttle, the movement of the plate must have been enough to get within the >2% differential.  When this happens with the OE ECU, the RPM's rise (like it did with the my Link Fury) and oscillate @ idle.  I figured it couldn't hurt to remove the intake tubing and use a cotton cloth with throttle body cleaner to give it a quick wipe down as opposed to removing the throttle body for the replacement.  A 30 second clean of the bore of the throttle body and the plate solved the problem.  

Adam, thanks much for the help.  I'll be using the forum a bit more in the future as I plan on a host of changes to the drivetrain of my Atom, aka Captain Proton.  Here's a reference pic for your/Links use should you choose; thanks again.

 

[Adamw]

Time will tell, but Im not convinced that would have been your problem.  

There are 2 TP sensors connected to the same butterfly shaft, so yes - if there was dirt of something stopping the blade from closing then they would read higher than normal when closed - but since they are both connected to the same shaft they would both read higher by the same amount.  

The fault code you had was due to the sensors reading differently from each other.  One was showing 3% more than the other.  When the sensors read different the ecu has no way of knowing which one is correct.  

[Captain Proton]

If the problem resurfaces again, I'll post on this thread and likely swap the throttle body out.  As you noted; time will tell.  Thanks again for your assistance

[Captain Proton]

I wasn't sure whether I had the newest firmware update and if not, should I update it?  FWIW, I didn't do any of the tuning so my knowledge of processes in minimal at best.