Throttle position measurement

This is the Forum for all your Peugeot Technical Questions, Problems or Advice.

Moderator: RichardW

David_CH
Posts: 46
Joined: 21 Jan 2020, 13:29
x 3

Throttle position measurement

Post by David_CH »

Hi there ! I’m new here so expect many dumb questions:-)

Today I was playing with a cheap odb2 scanner, just to read some values and try to understand the meanings.

One thing took my curiosity : the Throttle position % was at near 15% even with the engine off and the pedal not pressed. If I press the pedal completely I read 80%

Is this normal ? Shouldn’t be likely 0% to 90%at least ?
76C5CB53-45BE-41EB-B1D3-4FBC4BC2C6EC.jpeg
Last edited by myglaren on 23 Jan 2020, 09:19, edited 1 time in total.
Reason: Image rotated

ekjdm14
donor 2020
Posts: 1790
Joined: 19 Jan 2015, 18:42
x 197

Re: Throttle position measurement

Post by ekjdm14 »

Pretty normal from my experience (206 GTi180 and 1.4i Verve on Launch handheld scanner) Both of those seem to sit around 12-16% engine off or idling, 87% if I bury the pedal in the carpet... I don't fully understand why, but I imagine it's more to do with the ECU's capacity to open/close the throttle further if it needed to (for example if it was tight toward the end of it's travel) & probably based on the current rating or % of PWM modulation of it's driver circuit.

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: Throttle position measurement

Post by GiveMeABreak »

Because these 'drive by wire' systems no longer have a cable connection to the motorised throttle housing, they use an analogue potentiometer in the accelerator pedal mechanism to send data to the engine ECU and this commands the butterfly housing motor to open close.

These use varying electrical voltages (OCR) on the 2 tracks:

Throttle open:
Voltage between Earth & Track 2: 0.5V
Voltage between Earth & Track 6: 4.5V

Throttle Closed:
Voltage between Earth & Track 2: 4.5V
Voltage between Earth & Track 6: 0.5V

But in order to be able to detect short circuits to Earth, the range of 0V to 0.5V is used and to detect short circuits to positive, the range 4.5V to 5V is used. So that's why the values are not absolutes and looking at the percentages.


Motorised Butterfly
307 Throttle B.PNG
V: Position of the butterfly at rest (ignition off) or "limp home" position in the event of a failure.
W: Position of the gas butterfly with the ignition on or at idle.
X: Position of the butterfly at full load.
"m": Force of the butterfly motor.
"n": Force of the spring.

With the ignition off, the "limp home" spring holds the butterfly open (phase V).
When the ignition is switched on, the injection ECU controls the butterfly to the idle position, countering the force of the "limp home" spring (phase W).
Engine idling; the gas butterfly moves so as to supply the necessary air flow to the engine (replaces the idling regulator stepper motor).
From 1500 rpm the injection ECU controls the gas butterfly in the other direction to assist the "limp home" spring (phase X).

The position of the throttle is monitored by the injection ECU (potentiometer incorporated in the butterfly unit).
The injection ECU cuts off the supply to the throttle housing if certain faults are present.

David_CH
Posts: 46
Joined: 21 Jan 2020, 13:29
x 3

Re: Throttle position measurement

Post by David_CH »

i like A LOT your technical answers Marc !! understanding how things work is my passion

ekjdm14
donor 2020
Posts: 1790
Joined: 19 Jan 2015, 18:42
x 197

Re: Throttle position measurement

Post by ekjdm14 »

This is interesting, and makes perfect sense now you've mentioned it. Could I pick your brains a little further on the limp home function, Marc? From how our 180 acted when it lost control of the throttle body, I imagine it controls revs using timing and a lean mixture (idle was around 1100rpm, sounded like it was running very lean and (perceived) ran hotter than usual. Slight throttle pedal application resulted in revs coming up slightly and starting to sound more normal until it reached the limiter at about 2000rpm when it would cut fuel, rinse and repeat.)

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: Throttle position measurement

Post by GiveMeABreak »

On this particular engine (EW10A) 2.0i 16v 143 it uses the Magneti Marelli Injection ECU.

So the Accelerator pedal sensor registers the driver's demand (acceleration, decelaration) and delivers this info to the injection ECU.

The Injection ECU then uses this data:
  • To determine the opening of the motorised butterfly
  • To determine the injection time
  • To determine the ignition advance
In the event of a problem, the Engine ECU uses the following principle backup modes:
  • Limitation of engine speed
  • Limitation of engine torque
  • Engine stopped
  • Cutting of the motorised butterfly unit command
A backup mode will kick in if there is an issue with the:
  • Motorised throttle housing
  • Accelerator pedal sensor

David_CH
Posts: 46
Joined: 21 Jan 2020, 13:29
x 3

Re: Throttle position measurement

Post by David_CH »

“limitation of engine torque” , this is my feeling when I accelerate from red lights (and only in 1st gear), then it kick in at 2000 like a normal 140hp engine.
Can’t wait to receive my Lexia and see if there’s something into the ecu

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: Throttle position measurement

Post by GiveMeABreak »

It should help of there is a fault code - or will at least point you in the right direction. :-D

David_CH
Posts: 46
Joined: 21 Jan 2020, 13:29
x 3

I hate DBW !! (drive by wire)

Post by David_CH »

I've discovered why my car has some sort of "lag" when i press on the pedal, especially on 1st gear.

This damn drive by wire thing ! :oops: :oops:

I suppose there is no way to reprogram the response time even with Lexia right ?

If we are allowed to discuss ecu tuning in this forum, do you know if some Tuning shop has found a way to remap the ecu and give us back our "natural" throttle response ? I don't want more power, i just want a real lion reaction :) (i miss my Peugeot 306 rally car)

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: I hate DBW !! (drive by wire)

Post by GiveMeABreak »

No you can't programme it with Lexia. That doesn't do anything except tell the engine ECU when you request acceleration and when you release it. The electronic Accelerator is just as quick as a mechanical version. Your problems, if there are any will be further up the line unless the accelerator pedal potentiometer is faulty - but it has safeguards and a backup track that always compares the data. If it was faulty, you would have a fault code and it would go into limp mode.

David_CH
Posts: 46
Joined: 21 Jan 2020, 13:29
x 3

Re: I hate DBW !! (drive by wire)

Post by David_CH »

It looks like the do this as a purpose, to leave you the fun... like removing the handbreak lever and put in a motorized lever...

Well.. i still haven't received lexia.. i'm curious to see if there is some faulty code.
There is an indicator showing me that the engine is into "limp" mode ?

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: I hate DBW !! (drive by wire)

Post by GiveMeABreak »

Not always - it depends on the fault code. Sometimes a fault will not trigger the Engine Management Light, but will still put the engine into back up mode - again depends on what the fault is.

Hell Razor5543
NOT Alistair or Simon
Posts: 10218
Joined: 01 Apr 2012, 09:47
x 908

Re: I hate DBW !! (drive by wire)

Post by Hell Razor5543 »

This may NOT be relevant, but on some PSA vehicles there is a cable between the pedal and the potentiometer. If this has any slack on it you can get a delay between pressing the pedal and the engine responding. If your 307 has this type of setup it could be worth checking to see if the cable has any slack, and correcting it (if there is any).

User avatar
GiveMeABreak
Forum Admin Team
Posts: 19443
Joined: 15 Sep 2015, 19:38
x 1871

Re: I hate DBW !! (drive by wire)

Post by GiveMeABreak »

He doesn't have a mechanical set up James - I already ascertained this before responding.

User avatar
Michel
Posts: 1750
Joined: 29 May 2017, 13:50
x 327

Re: I hate DBW !! (drive by wire)

Post by Michel »

My Yamaha MT-09 has DBW for the throttle. It's nowhere near as nice as a proper mechanical setup. Common complaint is that it's quite jerky. It's actually a problem with the throttle mappings, there's plenty of tuners who will flash the ECU to correct it. It smooths the throttle out, and helpfully removes the 5th and 6th gear rev limiter :)