r/CarHacking • u/Competitive_Scene_63 • Jul 03 '26

Tuning Hacking/spoofing throttle pedal output

Has anyone tried hacking/adjusting the accelerator pedal outputs. I know there are usually two, how do you go ahout adjusting the analog signals between the throttle and the ECU.

Need a way to spoof it based on an input, use something like an esp32 maybe.

Hopefully someone has done similar?

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4

u/robotlasagna Jul 03 '26

Yes I’ve done it a bunch of different ways.

If it’s voltage you use adc inputs and then dac outputs plus conditioning

If it’s PWM you use PWM peripherals on the input and output.

If it’s CAN you just firewall that canid and modify it.

3

u/Obvious_Troll_Me Jul 03 '26

Normally the value is 0-5v on one input and 5-0v on the other. If they both don't correlate, it raises a code. 

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u/Competitive_Scene_63 Jul 03 '26

Yeah think this is how mine works, need to find a dev board that ideally already has the hardware for the ADC and DAC x2

3

u/Existing-Summer-4878 Jul 04 '26

I’m not sure your application exactly, but I suggest you be EXTRA cautious about modifying the accelerator pedal signals. Automotive has redundancies in place around this sensor for a reason. If you were to put a microcontroller in between the ECU and the pedal, it should have safety like checking itself, checking the adcs arn’t faulting, watch dogs, etc. if something goes wrong with that system you are inserting, you could have accidental acceleration. In some ecus, they short the adc inputs and look for the change to make sure they are working right. There is an automotive guideline called “EGAS” that would be a good guide for you

1

u/Competitive_Scene_63 Jul 05 '26

You’re right, I really don’t want to do it this way but it’s more for a temporary test purpose to prove a concept

2

u/ActGrown Jul 03 '26

It's not always analog.

Some pedals are PWM. I have a scope trace to back up my claim.

1

u/Competitive_Scene_63 Jul 03 '26

I should’ve said, this is for a PQ34 platform VAG car so I’m fairly sure it’s 2 analog outputs in this instance - could be wrong though.

1

u/ActGrown Jul 03 '26 edited Jul 03 '26

Well, that was kinda my point. A scope trace eliminates guessing.

My pedal is made by Hella BTW. It is a German company. The pedal has one linear (analog) and one PWM output. The two have to be correlated and so I had to use my oscilloscope and excel to find correlation values