GDT70-49 Posted October 10, 2023 Report Share Posted October 10, 2023 Hi, recently I have been triggering the following error "ECU Fault Code 77: APS(main) /APS(sub) tracking Error". Usually after a period of extended idle, but only recently i.e. I don't think this happened before. However, perhaps I never idled for this long... Can you confirm that I have understood the logic correctly for how this error gets triggered? Error statement - if the percentage difference between Main and Sub is >6% for more than 1s (fault delay) the error counter is incremented by 1. At that point I assume the fault delay restarts? When error counter exceeds 100 fault condition is triggered? Is the error count retained between starts/power on, or is it reset? I can see that I can edit the fault delay period, currently set at 1s, but is it possible to edit the 6% somewhere? I realise that editing these is masking a problem, but I have an IVA test on Friday and I need a temporary fix . If I set the fault delay to 5s is that likely to temporarily 'solve' the problem? As for the underlying problem would you agree that the following could cause it: Electrical noise. Mechanical slop between pot1 and pot2. poor quality contacts in the pots. wiring contact integrity. Anything else? The pots are fed from the ECU 5V outputs and grounded back to the ECU. Thanks, Carl. T70 F136 VVT Carl Aug'23.pclx Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 11, 2023 Report Share Posted October 11, 2023 The error accumulator increments faster depending on how much error above the 6% you are. Once you are under the 6% error it counts back down towards 0. So, this allows you to have significant error for a short amount of time or less error for a longer amount of time. When the hardware is ok, the accumulator should almost always sit at zero with only very brief spikes occasionally during abrupt transients etc. Log the raw voltages, APS sub and main, 5V, battery voltage, and the error accumulators to see what is going on and the likely cause. I would be very cautious driving it and do not turn off the safeties. Quote Link to comment Share on other sites More sharing options...
GDT70-49 Posted October 11, 2023 Author Report Share Posted October 11, 2023 Ah ok, thanks Adam. So, that being the case, if it occurs a short time after start, as it did yesterday, that would suggest a significant delta error in order to breach the 100 quickly? I will do the log as you suggest and get back to you. It might be at the weekend. I have ordered replacement sensors as a precaution right now, hope they arrive tomorrow... The 6%, is that of the 5V i.e. 0.3V or is it of the range? i.e. 3.97-0.38=3.59V x 6% = 0.215V Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 11, 2023 Report Share Posted October 11, 2023 6% "AP". So 1 sensor is reporting say 12% AP, the other would have to be reporting 18% AP. On 10/10/2023 at 9:51 PM, GDT70-49 said: Mechanical slop between pot1 and pot2. It would be pretty unusual to have two seperate pedal sensors? You would probably be better to replace with a "dual track" sensor if there are in fact 2 seperate sensors. Quote Link to comment Share on other sites More sharing options...
GDT70-49 Posted October 11, 2023 Author Report Share Posted October 11, 2023 Well you see.... the pedal-by-wire is a unit made by me. It does have two sensors as per the attached. I will investigate a single unit to see if I can accommodate. Quote Link to comment Share on other sites More sharing options...
Adamw Posted October 11, 2023 Report Share Posted October 11, 2023 Provided both sensors have spring loaded centre hubs to take up any backlash you would think they should work ok. Some TPS sensors dont have the sprung hub so if that's the case you may be able to solve any backlash by dropping a blob of RTV in each hub before assembly. Otherwise for a dual track sensor, the variohm ones are easy to find and one of the more affordable. Example: https://www.efihardware.com/products/3150/dbw-contactless-throttle-position-sensor-variohm Or there are many OEM "cable position" type dual track pedal sensors that you could pick up from a junk yard. Honda, Merc and VW from the early 2000's are the main ones I have seen. Honda example: https://www.efihardware.com/products/3297/honda-dbw-accelerator-pedal-sensor Quote Link to comment Share on other sites More sharing options...
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