Hi there.

I have a problem, and don't have much info on it. Earlier I made a thread about it, and it all looked like coil problem. But since yesterday my mechanic diagnosed this: there is no problem with coil but with some part named "TP sensor" (OR SOMETHING LIKE THAT) which has something to do with air intake as I have understood. Also, he said that he used to fix this part to VW and other cars but he never tried that with Fiat. It probably means I will have to replace it. Is it expensive?

At that moment, the error was just listed in "error history", he reseted the car computer and told me to come when the error "is on" meaning I have to wait for the problem to reoccur and then go directly to him so he could determine the errors code.

Well, it did, exactly today. The engine started to lose its strength, I tried to hit the gas but it didn't help. It has turned off. After three ignitions (1st and 2nd failed) everything is fine. So the car losses its RPM during driving or refuses to ignite sometimes.

Everything else is fine, there are no other errors. I am thinking to try to make the car to trigger the problem by driving it like I want to punish it and then visit the service with the "error on".

So, anyone: do you have anything to explain me about this "tp sensor" problem?

Thanks.

Ups! :bang: The car is Stilo 1.8 16v, dynamic, 2003.

Sounds like it's the Throttle Position sensor circuit


That's it here N75

You may not need to replace it as it's very expensive, there may just a problem with the communications from the potentiometers there. It means the ecu has no idea where the throttle position is and doesn't know what to do so it will often put the car in "limp" home mode or just give up as it is receiving no feedback

Obtain the actual fault code numbers

I was offline during the weekend, thank you for your reply. And thank you for the picture, hope it will help...

Guess what? The problem reoccurred once again two days ago. Car lost its RPM at app. 100km/h while I was taking over a truck! Man, not a good moment. I had to pull aside and restart the engine after 3 attempts. I HAVE to fix this immediately.

My mechanic said he has to look for the code he got from diagnostics in a book. Also, as I have mentioned, he said that code may vary depending on case if the reading is from cars "error history" or when the error is actually "active".
Unfortunately, I haven't asked him for the code number at the moment, which crossed my mind later, so I could post it here. It looks like I will have to visit him again and ask for it.

I have a question: how can you tell what is it? Is there a code base online or someone has the numbers?

Here is a fault code list
http://www.carclinicmagazine.com/fault_code_library.html


If you've ever played with one of these before then you'll know the resistance alters as you rotate the control

You have two of these in the throttle body (although a lot smaller!) which tell the ECU where the throttle postion is.

It should respond like this


The is engine rpm v throttle position and they should be smooth and follow one another. This is a picture of my Stilo throttle response so yours should be the same. If the trace isn't smooth like this then there's a problem. Any sharp changes or "drop outs" and the ecu won't know what's happening and will limit throttle response or shut down for safety reasons

It's dangerous to suddenly lose power but not as dangerous as suddenly getting full power when you didn't want it

Because your problem is intermittent, you have a poor contact somewhere in that circuit, it may be external and very likely is- at the throttle body connector or at the ecu - or internal in the throttle body. I'd clean up the connector terminals at the throttle body and ecu

:worship::worship::worship:

You have to be worshiped! Are you doing anything else but replying to me?

Once again I am looking at your pictures. The last one is in color and I have no idea where it came from! I mean, the device my mechanic uses is probably from XV century - its portable with monochromatic screen.... this all is becoming little confusing to me. Yet, I am generally good with understanding such things but this all is going to be interesting. I am thinking of taking all this material to service but it is possible that even they will not chew this easily.

It is possible that I am going to obtain the code in next hour and I will post again.

Here THEY are - 2 codes:

P0120 Throttle Pedal Position Sensor/Switch A Circuit Malfunction


and

P0638 Throttle Actuator Control Range/Performance (Bank 1)


So, where are we now? :idea:

Ok your throttle pedal position sensors are on the throttle pedal shown as K55 here. What engine do you have as cars vary?



Again there are two potentiometers there and a poor contact at the connector will cause problems. It's often caused by dampness, i.e wet boots

The signals from the throttle pedal go through the famous D4 connector and that has problems especially in the wet (See Stilo Guides)

And then there's the brake light switch which, when it malfunctions confuses the car into thinking the brakes are on and the throttle pedal is being applied at the same time and it doesn't like that

P0638 means that the desired throttle position and the actual measured throttle position did not match within a specified limit for a specified time

OK. The engine (you are asking for it?) is 1.8 16V November 2003. And dynamic, which is probably irrelevant.

As I have understood, you have described the 120 error mainly. The brake switch has been changed this year, maybe it has worn off as it was new, or its mounted sensitively so now after 6 months I have the brake-throttle problem you have mentioned?

Now, as for dampness, I don't give that much chance. Dry weather .

I am not a mechanic, so should I try to mess with the the pedal? At least, I can clean the connectors, right?

638 is surely a job for an expert... I think.

Because there's an intermittent loss of communications somewhere between your throttle pedal and your ecu and then on to your throttle valve, finding just where it is will never be that easy.

The throttle pedal itself is awkward to get access so go for the easy ones first. Find the D4 connector- under the engine fusebox- and use come contact cleaner on the contacts, leave to dry and reconnect. Do the same with the throttle valve electrical connector. You've then cleaned up the most likely sources of the problem in the circuit

Electrical tests on this circuot are best left to an electronics technician

I've found there are millions of experts and millions who are incompetent and many are both!

OK. I have read something earlier here on forum concerning gas pedal, (replacing the break switch) so I now its a little bit tricky. Also, messing with such electronics is not something I do. The idea of doing things myself is to reduce some time and avoiding of getting charged for things that can be fixed easily. There are examples here that some people have spent money for things without solving the problem just because someone else wants to earn easy money.

That is why I like to receive information from people who know the matter, like you do, and for that I am VERY grateful!

I will follow your instructions and post about the results.

Need To Make Some Registration On Examiner On Following Parameters:
Potentiometer 1, Pot.2, Throttle Position, Potentiometer 2 Of Throttle, All In The Same Time.

More: Clean First D004 Plug

Thanks Malin.

If cleaning fails - HOPE NOT! - examiner is going to have some more instructions.

you'll see on graphics the fail. One of these four.

Hm...:chin:

Am I right thinking that diagnostics needs to be performed while the error is "on", that is while engine is in condition of failing?

In my case "failing" is that occasionally (2-3 times in last 7 days) car lost RPM while driving and turned off. It could ignite afterwards, but with few unsuccessful attempts. Because, when it turns off, after restart the error is in a "cpu" history which means diagnostics just gets the codes I have mentioned before and cannot measure data from sensors to pinpoint the error.

Right?

SO FAR SO GOOD!

After cleaning four plugs - D004, throttle body connector and two more with contact cleaner the problems are gone! There are no symptoms of 120 and 638 error so far.

Thanks to:

Malin Popescu and specially to DECKCHAIR5!

Good stuff! Nice cheap fix there then. Hope it lasts

Well, my mechanic still does not know that this time he is gonna get short for some money by giving me the codes...

And cheap? Some time spent here on forum and 4,69 GBP for the contact cleaner. :slayer:

Just thanks to you! :worship:

if after a while it reapears, shortcut the D4 plug with wires of same thickness.