Citroen C5 I, 2004, ECU flash, tow wiring, alloy wheels

[DoomsDay]

Hello everyone!

I am looking into this forum for quite some time now (since I have my C5). However, I cannot find any good instructions, info and recommendations about next few things I will talk about.

Firstly, my car is Citroen C5 I Estate Exclusive, 2004 2.0 HDI with 80kw/109hp and has now 225 000 km.

I bought it as my first car, because it was in my price range (paid 1450€ for it) and has more or less all I want from a car. (leather seats, comfy ride, lots and lots of space, is diesel and I have a friend that had 2 already (now he has third one, and with each he made about 500 000km). ohh and it is just amaizing

However there were some things "wrong" or "missing" or I just wanted to change them. So so far I DIY:
- installed heated leather seats (just heating pads + connecting wires under original seats)
- Pioneer radio because with original, I couldn't get "clean" sound at all. (maybe something was wrong or it is just bad, not sure, never really checked)
- full led lighting ( + got on ebay some nice "Citroen logo" led lights for door lighting -> when u open doors, on the floor it is Citroen Logo instead of light, ebay)
- Releathered steering wheel (it was in semi-bad shape)
- did all kinds of little things and services myself since I dont really trust anyone to do anything on my car (unless it is something that I don't have needed tools)

What is next to do:
1.) trying to get "wood" look on my gear shift knob (at the moment have original, that aluminum looking finish that I don't really like) (deciding between 2)
2.) getting new indoor door handles (I cannot find this at all, If anyone has any info where to get them, please help me) Important! I do not mean handles that are used to open the door (those are fine), I want the handles on the door that are fixed. They are weird greish looking now, I would like to have "woodish" look (I can add pictures later if I didnt explain it good)
3.) Looking intoo aftermarket wheels 18" (I can get some really nice from AEZ for just 350€), problem is, that I dont think I will pass homologation (maybe if I get tire thickness 40 or less) anyone has 18" wheels? (with 18", is it still OK to use hydraulics on max (speed <= 10km/h) or the tire is rubbing inside? )
4.) Doing DIY of towing (need some help here)
5.) Looking into flashing ECU (any1 did it, what do they recommend, so far I didnt find anyone to say "you should get XXX for YYY and it works great")

I would like to use this post, to answer/talk/solve all the above stuff, so some1 like me in the future, can find all the answers in one place.

So I need some help with where can I find "2.)", some additional info about "3.)".
For "4.)", so far I have everything at home (in parts), need additional help with wiring cables.
I have cleaned rusty iron etc. Now in the process of rewelding a bit more to be sure all is good. I also have already all new parts for wiring stuff. However here is slight problem At the back/boot, near the spare tire I found some "black box" that wires go in and then back out. (I think they are used for back lights, back parking senzors, 12V at the back and for button to "lower/raise" the back part of the car. I bought 7-pin Bypass relay (check picture, hope it works)

This is basically working like this: You take "main" cable, that has power when car is ON from the fuse box at the driver side (beneath), you loot it with new cable, then use new cable to go all the way to the back and plug it into this baypassRelay. Then u connect 7 wires form Relay to correct wires (light, blinkers etc) and thats about it. (if you do not do it like this, there CAN be problems with "faulty lights" messages, because it drains more power etc). But where is the problem? Well, I read somewhere, that doing with Baypass, that you will not pass homologation, because doing it like this, you do not "tell" the car, that you are towing something and you do not have something like TPO sensors enabled (car knows you are towing) and with that sensor car knows how to react with ESP when something bad happens (trailer starts sliding, trailer tire blows up, etc). If I want this, I need to buy "genue wiring kit" for citroen and thats more than 100$ so idk. Important to note is, that I will tow ONLY 2 bikes (road bike and dirt bike), so aprox 500kg of weight and thats about it. I am not planning to tow boats or something heavy. So there are 3 questions:
1.) Can I use Baypass and do homologation successfuly or they will say it is a No-go?
2.) Do you think I should do it with "genuie" kit or do it as planned so far?
3.) Can I use that "black-box" at the back without additional Baypass somehow?

And about flashing ECU... Omg I read so much about this and as far as I know you can remap the ECU or plug tunning box with X possible modes. Some say 1 is better, some the other. Me personally, do not care, as long as I can do it in a way, to "protect" the engine and not overdo it. That being said what I know so far:
Citroen C5 I with 2.0 HDi engine are 3 types.
- 66kw/89hp (2.0 HDI)
- 80kw/108hp (2.0 HDI)
- 100 kw/134hp (2.0 HDI)

That being said, since I have 80kw, Theoretically speaking, I could have 100kw and "engine" would be "safe", because otherwise I dont think they would make it in the first place. QUestions are:
1.) Can I just buy used 100 kw/134hp (2.0 HDI) ECU and replace it with mine? (correct me if I am wrong, but I think that car wont start because ECU is linked to car Key and other ECU stuff so car would not working at all)
2.) Do you have any recommendation which tunning box to buy? (if you used it for more than 1 year or more to get better feedback)
3.) So far what I found to be "good" is something like this: "https://www.chipexpress.com/products/ci ... boxes/321/" (chip express)
and TDC (https://www.ebay.com/itm/Power-Box-CR-D ... 1904864100)
Do you think any of this should be good or I should stay away/go with something else?
4.) Do I need to upgrade intercooler as well after tunning or not really if I do it in this scale?
5.) Important to note, I drive my car on highway 100km in 1 direction, twice a week, speed aprox 120km/h (not lots of km/year I know ). There are some short distances during the week to get to the store (I know, not the best for diesel but nothing I can do about it)

During this post, I will add additional pictures about everything and also findings for future C5 owners.

I hope this post is not too long, if I missed answers on my questions I apologize but I really did not find them.

Best regards,
Doom

[GiveMeABreak]

QUestions are:
1.) Can I just buy used 100 kw/134hp (2.0 HDI) ECU and replace it with mine? (correct me if I am wrong, but I think that car wont start because ECU is linked to car Key and other ECU stuff so car would not working at all)
2.) Do you have any recommendation which tunning box to buy? (if you used it for more than 1 year or more to get better feedback)
3.) So far what I found to be "good" is something like this: "https://www.chipexpress.com/products/ci ... boxes/321/" (chip express)
and TDC (https://www.ebay.com/itm/Power-Box-CR-D ... 1904864100)
Do you think any of this should be good or I should stay away/go with something else?
4.) Do I need to upgrade intercooler as well after tunning or not really if I do it in this scale?
5.) Important to note, I drive my car on highway 100km in 1 direction, twice a week, speed aprox 120km/h (not lots of km/year I know ). There are some short distances during the week to get to the store (I know, not the best for diesel but nothing I can do about it)

During this post, I will add additional pictures about everything and also findings for future C5 owners.

1. No you can't. The engine ECU is linked to the BSI and the Key Fob Transponder / Circuitry.
2. Personally, I wouldn't bother - I tried one on a MK II years ago and there was no difference and ended up returning it. Stick with what you've got unless you have a real need to do it. If you are going to have an engine remap - expect additional wear & tear on components. I'm not sure in your country what the law is, but here you are required to inform your insurance company of any extra power increase, or it may void your insurance if you don't.
3. See [2]
4. If you have a manual transmission, make sure your clutch and flywheel are in good condition, as a remap will put extra strain on these components. A proper remap should provide turbo power across the range - depending on the tune that you opt for (economy or performance / sport etc.)
5. You haven't mentioned whether your car has a Diesel Particulate Filter or not, but good long runs like you have mentioned are fine and so are short runs ok. The issues often arise on constant short runs where the engine really never gets up to temperature for very long.

On the other matters: The black box at the rear is likely your Parking Assistance ECU. Don't interfere with that or you will likely cause issues with the system.

Parking Assistance ECU C5 MK I

I'm not quite sure what you are asking about towing - but there are OEM wiring harnesses available from PSA designed to interface with the car's ESP system (if you have this fitted) that allow a special mode and programme for towing - you don't have to be towing anything heavy - it doesn't matter in relation to the programme - it just uses a different software programme when applying emergency braking or when a skid is likely / detected to account for towing. It also deactivates the rear parking assistance when connected up.

There are aftermarket kits of course that are not so clever - but it is entirely your choice and budget.

Be very careful about altering / cutting / splicing wiring. The C5 is a multiplexed CAN vehicle that 'pulses' data along the car's data networks, so make sure you get a suitable wiring kit if not an original, which should be CAN compatible to be on the safe side.

[DoomsDay]

@GiveMeABreak

Thank you for your respond.
1.) no ECU/tunning box then
2.) I have no clue what "Diesel Particulate Filter" so will check Google and feedback later in the afternoon
3.) that is Parking Assistance ECU then yes, looks exactly like that.
4.) About wiring, you basically answered with what I wanted to know. I will go with "cheap Bypass" mode and see how it is before doing anything else.

And yes, will be careful thank you.

Also,
a.) Do you have any suggesting about aftermarket bigger size wheels?
b.) What about door handles? found some sample picture of what I am refering to:

Thanks for all the help and guidance so far.
Best regards,
Doom

[GiveMeABreak]

If you have your VIN - PM or post up and I'll tell you if you do or not have a DPF - some European models of this year did have one fitted on the 110.

As for the wheel sizes, Citroen only produced the Mark I with 15" or 16" alloys - so I would stick to those - several reasons - safety - vehicle specification, insurance, ESP (if fitted). Have a look at this guide from Continental = you can see that they tested the effects of the different wheel sizes on a Golf and the 18" - 19" wheels performed poorly, decreased economy and performance!

https://www.driving.co.uk/car-clinic/wh ... -your-car/

As for the door handles - yes they were are real problem on the C5s - they tend to be coated with some thin plastic type rubberised paint that is just so thin it soon peels off. I had a similar issues with the ones on my C5 X7 - the door puller handle trim inserts - so I took them all off (just the trim inserts) and rubbed them down (that didn't take long as they were so bad ). I degreased them, primed them a few times and got some custom paint the same as the bodywork made up in a small tin and resprayed them several times and then lacquered them with a few coats - now they are head wearing, shining and match the bodywork.

Also watch your LEDs - aftermarket headlamp kits are subject to new rules here in the UK for the new annual MOT inspection with many people (including the tester I know) having to remove them as they will fail the new tests. Not sure of your regulations though....

[DoomsDay]

Sorry but away from car atm, am at work (going there with bicycle) so will check that later. I researched about DPF and well... I think I have it and if I do, I am 100% sure that it hasnt be replaced yet... so being that said, 1 more thing to do
1.) Do you recommend cleaning DPF filter with just those cleaners u can buy for about 15$ (this looks like a big BS but never tried so)
2.) I clean DPF with air and hot water under pressure (can be seen on youtube, looks like it works fine)
3.) dont mess with it and just buy a new one

And yeah, will go the same way with those door handles I guess

And LEDs rules here are cough were already on when I bought a car cough
Tho I have Xeon so didnt change those (LEDs are changed just on the inside (below the wheel, below glovebox, under the door panels, in the trunk, 3 + 3 on the roof + position light on the front 2x + licence plate 2x at the back) LEDs were replacement for all 5W5 original bulbs.

[GiveMeABreak]

Best to check first whether you have a DPF or not - when you have the VIN code just let us know.

If you do, you will normally get a warning up requiring the additive fluid needing topping up - but before we get into that there may be no need as a lot of the 110s didn't have the FAP fitted.

I've replaced most of the internal LEDs too:

A few older shots - the photos make them look worse than they are - not a 'pimpmobile' I promise!

[JohnD]

This is basically working like this: You take "main" cable, that has power when car is ON from the fuse box at the driver side (beneath), you loot it with new cable, then use new cable to go all the way to the back and plug it into this baypassRelay. Then u connect 7 wires form Relay to correct wires (light, blinkers etc) and thats about it. (if you do not do it like this, there CAN be problems with "faulty lights" messages, because it drains more power etc). But where is the problem? Well, I read somewhere, that doing with Baypass, that you will not pass homologation, because doing it like this, you do not "tell" the car, that you are towing something and you do not have something like TPO sensors enabled (car knows you are towing) and with that sensor car knows how to react with ESP when something bad happens (trailer starts sliding, trailer tire blows up, etc). If I want this, I need to buy "genue wiring kit" for citroen and thats more than 100$ so idk. Important to note is, that I will tow ONLY 2 bikes (road bike and dirt bike), so aprox 500kg of weight and thats about it. I am not planning to tow boats or something heavy.

Your TEB7AS will work perfectly without causing your car to throw a wobbly. I use one in my present C5 and had one in the previous facelift model. Since I need a reliable supply without voltage drop for a caravan fridge and caravan battery charging, I took my supply through two 17amp wires directly from the car's battery via two inline fuses. The road lighting cables run from the 7N socket on the towbar, back to the TEB7 relay which is installed behind the panel in the load area. The wires fitted to the relay connect to each wire running to the rear light units. The law in the UK requires an additional warning in the car to show that the indicators on the trailer are working. That can either be by flashing light or buzzer. In addition I have a voltage regulated relay for fridge supply which only passes power to the fridge when the engine runs.

[lexi]

Sounds like OP has an original type 2.2hdi. I think they had parking sensors Dpf etc. If not then it must be Mk1 facelift. So either way you have a useful 130+bhp. Would be interested what welding was done and where on the car it was rusted.

[DoomsDay]

@GiveMeABreak Ok so my VIN (i hope this is it) is: VF7**************[VIN obfuscated, can be read by forum staff]************** . IT was on the front windsreen this is it right? (I did not check if I have DPF yet since lack of time, will do it tomorrow)

@JohnD thank you for the feeback, I am way more optimistic everything will work now

@lexi I do not understand what OP means and what was your reply refering to sorry. Can you explain more please?

Best regards to all,
Doom

[GiveMeABreak]

Ok so you have a MK I DW10ATED TURBO DIESEL WITHOUT FAP - so you don't have a Diesel Particulate Filter on your vehicle - so no need to go hunting round for one.

OP means Original Poster (you) - and Lexi thought you might have a 2.2L engine - but you mentioned in the first post already that it was:

Firstly, my car is Citroen C5 I Estate Exclusive, 2004 2.0 HDI with 80kw/109hp and has now 225 000 km

So could only be one of the 110s with or without a FAP (DPF) - problem solved with the VIN.

[DoomsDay]

Ohh I see. Thank you for clarification

Will post more pics and info over the weekend

Cheers,
Doom

[DoomsDay]

Ok, so quick update.

1.) repainted all letter badges and reglued them on
2.) Completed 1 side of tow iron restoration (1 to go next weekend)
3.) Polished the car and ceramic coat it
4.) Painted outside door handles in silverish to replace original color ones (not sure if gonna do it yet)

a.) Decided ECU flashing and tuning box is a final no-go.
b.) Loking into making my own trailer
c.) waiting for new window tint to arrive to finnish window tinting (should be this week)
d.) Wiring green LED indoor lights to "open mechanism"
e.) Waiting for shark fin antenna instead of long original one
f.) waiting for book "Citroen C5 2001-2008 Owners and workshop manual"

Some pics of my current setup (I know pics are not best quality sorry for that):

When you open door insted of light is this:

Will be updating when more stuff is done/added with instructions where needed.

[DoomsDay]

Another update since it was a while:

1.) Window tinting is now done
2.) shark fin antena is installed (if you do not have it, I recommend, it is very nice )
3.) Got the book for instruction manual, now doing all the services that were not done when needed (previous owner didnt bother doing them)
4.) Repainted inside door handles
4.) Towing stuff/kit is now all prepared, was brushed and then painted 3 coats with primal and then 3 times with some anti gravel pain on top of it. Rewired the new socket, this week probably I will install it on the car and plug all everything so excited about that

I will/can post wiring diagram for future use.

Hope you all having a great time,

Doom

[wurlycorner]

Welcome, only just caught up with this thread.

Only one thing to add, that tt's fine to use an after market (non OEM) bypass relay on a C5 Mk1 - mine has one.

As for the door handles, I haven't seen the covering on them fail in the way that X7 and other newer Citroens fail (a thin rubber coating that has absolutely no durability) but they do have a habit of going 'sticky'. I've just cleaned that off easily with a damp kitchen scouring sponge.

[DoomsDay]

Thank you for the feedback! Yes I also got rid of that stuff on door handles, then just sand it with 400, then 600, then 800, 1500 and 2000 and painted it black and on top of it put some clear coat-ish spray so its good enough now and should last some time I have 2 mayor issues now tho.... I tinted the windows and almost finnished doing the towing thing on and then I went to do homologation for windows tint... They were very surprised that I did it myself acting like its very hard thing to do and stuff. However problem is, that I need "tint certificate" in order to do homologation.... I was/am so pissed off bec I cant get it for some random window tint purchased on ebay. U can get it tho from certain people that "they" know and can give it to me, but of course need to pay quite some money for it... Same goes for fricking towing bar. For window tint I will just "modify" one from the internet or something, but what do you guys sugfest about towing bar? I have no clue where to get certificate for that. I have no clue what brand or anything is with that. All I know is, it is for C5 2001-2004 and that it is "hidden". You cant see it unless you get down on your knees and look under the car. Suggestions needed guys