Hopefully someone can help me out with this issue I’m having with my Bosch DBW throttle body.
The ECU starts to close the throttle at high rpm approx 7600rpm, this happens in tandem with the increase in DC out %.
The target throttle position and actual throttle position overlay perfectly into this point, where as expected the target remains as expected but the actual starts to fall.
I have double checked all wiring and no issues, have also fitted a new throttle body and redone the calibration yet the issue persists.
Incredibly frustrating, if any one has any suggestions then please do let me know.
I have a log I can share which I assume will be required to see if there is an issue I am missing
What does your DBW - Characteristic#1 table look like? is the Map targeting a lower Throttle Position at higher RPMs? Also, has your TPS been calibrated properly for the voltage it actually see’s? You can check under sensor setup/TPS.
I had a similar issue on a car where the Voltages were not set correctly so the throttle when pushed to the floor only actually reached 89% Throttle…so when the characteristics table got higher in the revs the throttle wanted to close down slightly.
providing a base map with your log may help as well but that is where I would start looking.
I had a similar problem with a customers car. The car was running for months without any issue and suddenly the same problem as yours appeared.
It was a ground problem! The customer didn’t wire the DBW ground to sensors ground, instead he just used the car body.
Log file is super interesting, it just starts closing at roughly the same RPM and its very repeatable.
PID is doing its thing, target error causes more DC but still starts closing.
Battery voltage is kinda erractic but its not falling off with rpm or anything.
No protections or errors present until above 7600 rpm, TPS value stays the same.
There’s random dips in the DBW error aside from above 7600 rpm, but seems to be of no consequence to the PID. This is most interesting because it looks like a drop out but its only shown in that channel, not the TPS 1 or 2 inputs (analog 1 & 2)
While I don’t have your cal file to see if there’s some other setting that somehow hasn’t been an issue up until now, and since you’ve tried replacing the DBW unit, that kinda just leaves wiring.
I have installed a bunch without issues but I know the connectors can be super finnicky.
My theory is that the engine is vibrating in such a way above 7600 rpm that the connector is loosing proper contact with one of the motor pins. This could explain the DBW error dips if its logging error’s at a faster rate then the position sensors are shown in the data logs (i think its 25hz in the graph logs)
What engine? is it solid engine mounts? How is the dbw motor attached to the engine?
Curious what pedal are you using? I see analog #3 and TPS are identical, and I’m assuming the plausible check is into analog #3…
I personally think there’s a problem with the electrical harness, and that’s causing the issue with the throttle.
I’m noticing a strange correlation between the closing of the throttle and the RPMs, especially with the DC injectors at the RPMs that are at 100%. It seems like the power ground wires are just too thin in diameter.
I’ve encountered similar cases where wires that were too thin were used. The throttle worked when the engine wasn’t running, but as soon as the engine started and the power ends began to work, the current simply didn’t flow properly.
Thanks for the input, I have continuity checked the harness time and time again and all is good.
In terms of ground wire size I believe they are sized appropriately at 0.75mm2, 1mm2, 1.5mm2 for, sensors, injectors, coils, DBW etc.
I have made a new harness to go direct from ecu to DBW throttle body to see if that helps the issue but i am not holding out much hope in all honesty.
I will post my EMU project file shortly, I do not think the issue is with the project file given the car ran perfectly for months before this issue started causing troubles.
