Odd noise on clio Tps pico trace

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Markrobbins87
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Posts: 1
Joined: Mon May 28, 2018 7:12 pm

Odd noise on clio Tps pico trace

Post by Markrobbins87 »

Hi all I am wondering if anyone could help me with a friend's car at work. It is a 2002 Renault clio 1.2 16v. The vehicle goes into a limp mode with very limited throttle as soon as the vehicle is started. The only DTC I can get out of the Ecu is p0255 for throttle pedal track C (snap on code reader). If the code is cleared it will stay cleared until the vehicle is started. I have checked the wiring at the pedal with a meter and i have 2 lots of 5v and 2 good grounds. I also have a sensible voltage out of the pedal on the signal wires. I have exactly the same voltages at the ecu. I have substituted a known good pedal with same part number and fault remains. I have removed the metal cover from the ecu harness as I have seen them chaff on the loom. I have also cleaned the white plug under the engine fusebox and cleaned all the fuse and relay connections too. I managed to get my picoscope from work and checked the signal and i have noticed with the engine running there is alot of noise but only when engine is running. The noise appears to be on the 5v reference going to both pedal tracks and appears on the signal out. Also the interference voltage spikes go positive as well as negative. Its worth noting that the clio has an early wiring loom which I am told have problems in the rubber insulated parts but the tps wiring doesn't go into this it runs down the back of the engine in split trunking and all looks OK. I have attached a picture for someone to look at. I appreciate any feedback given. Tha ks again.
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IMG_20180525_165433.jpg

Steve Smith
Pico Staff Member
Pico Staff Member
Posts: 1581
Joined: Sun Aug 25, 2013 7:22 am

Re: Odd noise on clio Tps pico trace

Post by Steve Smith »

Hello Mark and thank you for the post.

The noise you have captured is quite typical given the vulnerability of such a signal/voltage in the harsh environment of the engine bay, with high frequency switching components radiating EMI (Electromagnetic Interference).

PicoScope will capture and reveal this noise but we have a number of features you can use to quench or filter this noise from your waveform.

Could you take a look here:
https://www.picoauto.com/library/training/filtering

Just a thought, when you mentioned you borrowed your PicoScope from work, could you make sure you are connected to your PC via the Pico blue USB cable rather than any other substitute?

The Pico blue USB cable is quality assured for power and data transfer with superior grounding to minimize such noise

There is an interesting case study here where you can apply math to monitor the performance of your Pedal Track
https://www.picoauto.com/library/case-s ... ottle-unit

This does refer to a Throttle Assembly but the math application may be applied to your pedal.

Could you post your psdata file here capturing the outputs from your pedal whereby we can assist further?

I hope this helps, take care......Steve

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