C3 No Throttle Control

[tommy309]

Hi guys, Ive been lumbered with another wondereful job for a friend, Citroen c3 petrol, it starts and goes but it wont rev up when you use the throttle pedal, some ejit has been at it before.

so, the throttle pedal has been changed, so has the throttle body, out of curiosity i checked the injectors, and checked the intake manifold for leaks, but all is ok with that.

I hooked up the Lexia 3 and found the ecu, bsi and transponder and key are out of a scrapped car (at this point im thinking what the **** have i got myself into haha) ive got faults with both the motorised throttle and the accelerator pedal. However because the ecu has been changed, it wont let me do very much diagnostic work, as it says communication interuption as soon as you try to do any of the engine actuators tests.

Now i remember changing countless throttle bodys when i worked at Citroen, but this was always for engine management lights on, never because of this fault. I was wondering is it possible if the person that owned the car left this fault long enough it would develop into a burnt out motor or similar to cause this fault?

If anyone has a picture of a C3 throttle body could they send it to me as this one looks slightly different to what i remember and just want to make sure its the right one.

Any help at all would be good as im not too sure about what to do next...
Thanks Guys
Tommy

[DickieG]

Behind the glovebox tucked right up against the bulkhead is a connector used to transfer the loom across from the original LHD layout, that connector block is apparently a well known failure point, separate/cut off the two connector blocks and solder the connections appropriately.

[tommy309]

Right, ill have a go at that tommorow, although im quite worried that youve said that bcause theres a mountain of cut and joined wires in the footwell lol.
Thanks

[DickieG]

Note the colour of the loom entering the throttle pedal and trace them across, its not that difficult to find the right one as its attached to the bulkhead on its own.

[tommy309]

Thanks mate, not like them to make something easy lol, if i manage to fix this thing ill be amazed as its bee like this now for 2 years

[danielsydney]

Tommy, Let us know how this went and how long it takes you to fix?

[tommy309]

I will do mate, i plan to have another go at it on saturday, the guy is getting another throttle body for it, I will check the plug that was mentioned, and see if the previous guy has done anything with that. Im getting another throttle body becasue the other day i noticed when u switched the igntion on the throttle buttterfly open and then closed hard making a loud click noise, and it also makes a constant humming sound as if a motor is trying to turn but not able to..if you understand me. I would have thought if the connector was bad that th throttle would have just been inoperative rather than making it do odd things like that? But i have enough experience of french cars to know that logic doesn't always count for much lol.

Will let you know if i get it fixed, but im not holding out too much hope, although I would like to fix it as it seems to be a reasonably common fault although not that well documented it would seem.

[wheeler]

it also makes a constant humming sound as if a motor is trying to turn but not able to..if you understand me.

Im pretty sure thats normal operation, they all make a noise with the ignition on, it's like a quite high pitched whining noise. Do you have acess to another C3 with that engine to compare ? As for the open & closing when you first switch the ignition on, never noticed that but it may well be just a self test like many components do, The loud click is probably just the butterfly snapping shut same way as a manual one would if you opened it fully & let it go, some electronic EGR valaves do the same thing as a self test & some of them even do it a few times when you switch the ignition off to help keep them clean. Think about it logically its already had a throttle body, whats the chances of 2 being faulty ? and also you say it opens & closes fully when you first switch the ignition on, that to me says the motor is working & the wiring from the ECU to the throttle body is probably ok. Am i right in saying that the throttle motor does not respond to the pedal at all ? Well the pedal sends the signal to the ECU & then the ECU sends the power to the throttle motor, As you have access to lexia then you should be able to read live data from the pedal as it sound like the ECU cant see the pedal position info. The pedal has already been changed aswell so that really just leaves the wiring between the pedal & the ECU. What were the exact fault codes from it ?
Thats my theoretical thoughts on it anyway, I think i'd try the 4 pin connector behind the glovebox before i started to throw parts at it as its a well known problem spot.
How do you know its a 2nd hand ECU & BSI ? Different VIN's ? I dont see why this would cause you problems doing diagnostic checks with Lexia ??

[tommy309]

Yes its a second hand ecu cause its a different VIN Number, its also second hand pedal and throttle body, (yes i know this is as much use as a chocolate teapot) but hey,everything EXCEPT for the throttle body i know came from a working car, but the throttle body was from a scrap yard so god know if it was working. no i dont have another c3 or id have chaged all the parts over and then id at least be making SOME progress, i cannot read live data with the lexia due to the ecu being wrong for the car because when u do a global test on it, it will communicate with the ECU however u then go into the next screen it asks which ECU you have you put it in and it says ECU not recognised please check your choice and yes im definately selecting the right one. I should also mention that when i was at the car (havent been back yet) at begining it started and wouldnt rev, so after some checks and messing around, i started it again and it now starts with the throttle about 3/4s open, and again you still have no throttle input, im near sure its the throttle body, but i will check the plug, but i think the last guy has probably already done that hes a Citroen CT like, but that doesnt always mean alot.

[wheeler]

The fact that the ECU has a different VIN should not stop lexia comunicating with it.
If the other guy is a CT he should be well aware of the throttle extesion plug & done that first.

[tommy309]

Well yes he SHOULD but that doesnt mean he did lol. The lexia does communicate, it lets me read faults and check some parameters, but it wont do actuator tests on Injection ECU actuators, ive had cars like that before but it was that log ago now i cant mind much about it