Cruise Control Retrofit (C3 MK1 Facelift) - Help wanted!

[thenicolaibulow]

Hi Shtu!
Thanks for chiming in

As a quick and dirty test, I'd expect one of those switch values to change if you just unplug it.

Far as I know, it's just a switch, no canbus trickery.

Yes - that is the very first thing I did; disconnected the sensor to see if anything changed - which it did not.
Well, that was certainly because I was checking the sensor readout from within the ECU, which we have now concluded, is not working.
Had I been monitoring the sensor readout from the BSI instead, I don't doubt that I would have seen a difference with the sensor plugged/unplugged.
At one point I was even tempted to short out the two cables to verify..

But! never the less;
The BSI is clearly reading the sensor just fine - but the ECU. Since the ECU is in charge of the cruise control, there's now no doubt that it's the miscommunication between the ECU & BSI which has to be the problem.

Next step for me will be digging into the wiring diagram!

\n

[thenicolaibulow]

Having had a thorough look at the wiring digram provided in the Haynes C3 Owners Workshop manual, I was somewhat upset to find that the wiring seemingly does not match that of my car.
My guess it that its down a a few things crucial differences; The book is clearly written based on a RH drive car, and not a 'facelift' model. For example, my previous posts, I've noticed different layouts of the brake pedal switch wiring, when cross referencing with the information provided in this post.

In my car, the brake pedal switch only has a white, and purple wire (supposedly for the NO brake light switch) and nothing for the NC cruise control brake switch.

This diagnosis aligns nicely with the the fact that the BSI is reading the brake pedal fine (BSI must be reading the brake light switch) whilst the ECU is not reading the brake pedal correctly (presumably because it is expecting an input from the 'cruise control brake sensor', for which the wiring is not present)

According to the Haynes manual (which I am assuming to be incorrect for my engine)

[74] = Brake light switch, connected to the BSI with two (Ba, white) cables (In guess in my case Violet (Vi) and White (Ba))
[72] = Cruise Control brake switch, connected to the ECU with a (Rg, red) cable, in position F1 - where I found a baby blue cable connected, upon investigating the ECU.

So.. now the real question becomes: exactly which engine do I even have?

I have managed to get access to the 'Citroën Service, Electrical drawing for diagnosis and repair' - through which I can only assume that all forum posts containing wiring diagrams get their diagrams.
Unfortunately the tool fails to read the model based on my VIN. (Supposedly because the tool is running in an offline Win XP virtual machine..)
)

I think I have managed to pull the correct diagrams for my ECU wiring:

Here, if my interpretation is correct, there does in fact only seem to be two wires to the brake pedal sensor [2120] - although I don't see any indication of the wire color? only that the connector to the sensor should be green, which is the case. This diagram does point to the ECU wiring being different from what was described in the Haynes manual.

Can anyone help me identify which engine model I specifically have? I've seen examples of forum-oracles helping out in this regard in other posts

Best Regards,
\n

[GiveMeABreak]

Post your VIN up for me if your require a diagram. Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.

[thenicolaibulow]

Okay, upon running through dialogs in Lexia, I think I have narrowed my engine down to being a 8HZ, DV4TD.
And as such, the above diagrams should be the correct ones. Looking at diagrams for the brake light wiring, I noticed that when you look at the brake light, side by side with the cruise control diagram, all four pins in the brake pedal switch such in fact be present and connected, for cruise control to work (no sh*t).

So.. conclusion is the same as earlier - it does, sure enough, appear as though my car is missing two wires. God knows why. Even with all cost-savings in mind, branching out the selection of wiring harness' to have a non cruise, and a cruise harness seems wild to me.


Can anyone confirm that they are also missing these wires?
Could I just have been unlucky to have a car where these are missing on accident?

Is anything (besides time and sweat) standing in the way of me adding these wires between the ECU and the brake pedal switch?

[thenicolaibulow]

Hi GiveMeABreak!
I was hoping that you would chime in.

Thanks, here is my VIN: VF7**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Ok so just to get some clarification:

1) This is not going to help you as this vehicle was never fitted with Speed Control.
2) Wiring Diagrams are by specific vehicle, build date, options and system fitted, so logically, the system is NOT providing a diagram for Cruise Control or Speed Regulator as they were never options on this car (whether due to the 1.4 HDi Engine or not I can't say for sure, but we had both on our 1.6 HDi). So to confirm the system will not show me a diagram for this vehicle as the option was never there.
3) Therefore I can only show you the same diagram you have above from one of my previous posts, albeit in better clarity:

I believe that some vehicles can't have this system enabled / retrofitted.

[thenicolaibulow]

Hi GiveMeABreak,

Thanks for getting back to me!

2) Wiring Diagrams are by specific vehicle, build date, options and system fitted, so logically, the system is NOT providing a diagram for Cruise Control or Speed Regulator as they were never options on this car (whether due to the 1.4 HDi Engine or not I can't say for sure, but we had both on our 1.6 HDi). So to confirm the system will not show me a diagram for this vehicle as the option was never there.

Okaay, right - that makes perfect sense, as I was getting quite confused by the layers of selection menus in the Citroen wiring diagram tool. I went;
- C3 II, Entered RPO
- - Shape: 5 Door Saloon
Driving: LH
Motor: DV4TD Turbo Diesel
Transmission: BVM5
System: No ESP
ABS: With ABS

- - - Driving Assistance
- - - - Cruise Control / Speed Limiter
- - - - - Cruise Control
- - - - - - 'Mounting Bosch' - Assumed that this was referring to the ECU.

After which, only ' Regulator or speed limit' would give a wiring diagram.
A can only assume that this is what you would mean, by it "not showing you the diagram, as the option was never there"?

3) Therefore I can only show you the same diagram you have above from one of my previous posts, albeit in better clarity:

Right.

1) This is not going to help you as this vehicle was never fitted with Speed Control.

What exactly do you mean here?

I believe that some vehicles can't have this system enabled / retrofitted.

Okay. I guess I might have to throw in the towel then.

Although I am temped to try and inject 12V into pin E4 in the 32-pin, black connector on the Bosch ECU, whilst live monitoring the ECU with Lexia.
Since all other requirements (that i've been able to find!) for cruise control to work, I can't shake the feeling that this missing pedal switch feedback could be the very last ting needed to get the cruise control working.

Would you advice against it?

[GiveMeABreak]

Hi,

So yes, you have the most of what I was saying correct.
So I mean a 1) that because of what we've already mentioned, the system is never going to provide a diagram with speed / limiter on this model because it doesn't have the data, because it was never fitted on this model (so not going to be much help to you).

Further, without reading back through the post, the other essential component apart from the brake switch is the COMMS unit at the steering wheel. This probably won't have the necessary electronics in for speed control either, I suspect.

[thenicolaibulow]

Hi,

So yes, you have the most of what I was saying correct.

So I mean a 1) that because of what we've already mentioned, the system is never going to provide a diagram with speed / limiter on this model because it doesn't have the data, because it was never fitted on this model (so not going to be much help to you).

Ah, okay, right.

Further, without reading back through the post, the other essential component apart from the brake switch is the COMMS unit at the steering wheel. This probably won't have the necessary electronics in for speed control either, I suspect.

That might be the case - though I hope not.
To quickly reiterate the retrofit progress:

1. I have the dashboard screen show both speed limiting and cruise control icons which I can get to show, though not enable from the newly fitted cc / limit stalk.
- Leading me to believe the COMs and BSI correctly doing their thing?
2. BSI and ECU are configured to have both speed limiting and cruise control enabled.

3. Since the CC brake sensor is missing, and it is a NC switch, I suspect that the CC or Limiting never manages to enable, due to the ECU reading the brake as always pressed.

Appreciate the input!
\n

[ozvtr]

Although I am temped to try and inject 12V into pin E4 in the 32-pin, black connector on the Bosch ECU, whilst live monitoring the ECU with Lexia.
Since all other requirements (that i've been able to find!) for cruise control to work, I can't shake the feeling that this missing pedal switch feedback could be the very last ting needed to get the cruise control working.

Would you advice against it?

See if there is a wire in E4. If there is, trace it back through the fire wall.
How many wires are in the connector at the other end of the stop light switch "adapter" (in the cars' wiring loom)? 4? Could you need a different adapter? The stop light switch with 4 pins is white not green. The green and white connectors are not interchangeable.
I can't see a problem with applying 12v to E4. At least just to test the system.