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

[thenicolaibulow]

Hi Everyone,

I much appreciate the good tone and advice, found here in the forum. I have in recent months successfully completed a few repairs and upgrade to my C3 MK1 Facelift, thanks to posts here.
I hope that I can draw upon the collective troubleshooting experiences of this forum, in solving my latest upgrade endeavour; Retrofitting Cruise Control.

I was initially inspired to try this retrofitting procedure, based off of a forum post from another forum. (What are rules regarding linking to other forums? )
This guide outlines parts selection, modification to the interior trim, and the necessary configuration to be done in Lexia.

I started out by purchasing the cruise control stalk (from eBay, seemingly not OEM part), along side a VCI + Diagbox setup.
The stalk is the 'later' model with speed limiter & cruise control - and fitting it to the car was a straight forward ordeal.

It took me a while to get a proper working Diagbox/Lexia setup running, but as of recently I now have Diagbox 9.180 running natively on a Windows 10 Machine - with functional communication to the car, through Lexia.

Now, here comes the fun:
The guide i initially followed was for a C3 with a different ECU - the J34P, where as my car features the EDC16C34.
Okay, not big deal I thought; the EDC16C34 ECU clearly also has a configuration field for enabling / registering cruise control. [Cruise control: Present]
Likewise I also enabled speed limiter, in the "Injection" (ECU, right?) configuration, as the new stalk featured it. [Speed Limiter: Present]
As for BSI configuration, "Presence and type of cruise control" is now set to [Presence and type of cruise control: Cruise Control and speed limitation]
Lastly, in the configuration for the "Switch module under the steeringwheel" (Or, COM2000 I've heard it called), I verified the stalk button functionality. - Everything works as expected, with the exception of the rather useless memory buttons on the stalk..

Having clicked through most configuration menus, this was just about everything I could relating to cruise control.

Testing the car I found the speedometer display to correctly show icons for both cruise control, and speed limiting. However; I cannot get the car to react to either of these functions, or specifically; it won't consistently set the target speeds (rarely it does though), and in the few cases where it does, the engine speed is neither limited, nor kept. (Both CC & Limit icons still show 'off' )

I've read a lot of information on how to achieve this retrofit on various PSA models from the era. Some with the same ECU, some not. Though a few requisites seem to be consistent across the board:
The car (assuming manual transmission) needs to at least be equipped with:
- Clutch sensor
- Brake sensor

Though I've also picked up that a C5 MK1, fore instance, requires a 'redundant brake sensor' to be present, while a Berlingo needs to be mechanical, and not electric accelerator, for cruise control to even be possible.

My C3 has electrical accelerator, a working clutch sensor, however when live-monitoring the sensor readout, I notice that both the 'brake sensor', and 'redundant brake sensor' reads 'pressed' regardless of whether or not it is in fact pressed. - Do note that the brake lights works as expected. (Are the connections to the sensor 'normally closed'? Which module handles the brake lights, if the BSI clearly isn't reading the sensor properly?)

Furthermore after clearing all accumulated module errors, only one error is still present in the ECU: P1645.

Question:
1. Has anyone attempted to retrofit cruise control on a C3 1.4HDi MK1 Facelift, and if so, can comment on the required circumstances for it to work?
2. Does anyone know whether the ECU error, or that lack of proper BSI brake sensor readout, could be reason why the cruise control is not working?

Thanks in advance,
All the best
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[RichardW]

Those are Lexis readouts, what does Diagbox say? If the BSI is seeing the brake pedal pressed that will stop the cruise working. Light switch is normally open, close to light; redundant cruise switch is the other way around.

Fault code suggests 5v reference is missing; but surprised it runs if this is really the case!

[thenicolaibulow]

Hi Richard!

Those are Lexis readouts, what does Diagbox say?

I thought that my C3 would be too old to have 'actual' diagbox support. Isn't Lexia the way to go here?
Once the VIN is entered in diagbox i'm prompted to type an RPO number, followed by either 'lexia' or 'scantool' - both of which launches Lexia.

If the BSI is seeing the brake pedal pressed that will stop the cruise working.

Okay, thanks for confirming that. This gives me a path for further diagnosis.

Light switch is normally open, close to light; redundant cruise switch is the other way around.

When you say light switch, are you refering to the light stalk on the steering rack?
Can you elaborate?

Fault code suggests 5v reference is missing; but surprised it runs if this is really the case!

Okay! Which modules are powered on the 5V rail? I can only assume that I would be able to measure it there to confirm.

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[ozvtr]

The brake pedal data should come through the CAN BUS from the BSI. What is the BSI saying?

The brake switch has 2 sets of contacts. A normally open (NO) and normally closed (NC) set. The NO contacts are directly connected to the brake lights and monitored by the BSI. When the brake peddle is pressed these contacts close. The second set (NC) or "redundant" set, open when the brake peddle is pressed. They are also monitored by the BSI. This whole thing is to ensure that the brake switch is working correctly. Generally speaking, items on the CAN BUS only pay attention to the "redundant" set of contacts. It's not uncommon for these sets of contacts to malfunction. Automatic shifters "lock out" because of this problem.

The engine ECU uses the brake peddle data as a normal part of it's operation, irrespective of whether cruise control is fitted or not. That data should reflect the brake peddle position at any time.

If your car is a manual then "Clutch switch fitted" should be yes and the clutch switch (in the actuator section if the BSI) should reflect engaged and not engaged.
You should go into the actuator section of the "BSI" and "switch module behind the steering wheel" and check that all the switches are working.
My guess is that the engine ECU is not getting the correct brake switch settings and it doesn't like it. Undo all the bits that you have fiddled with and see if the engine ECU starts getting the brake peddle data.
Then add bits one at a time.

[ozvtr]

I would clear the P1645 and see if it returns. It seems erroneous, unless you live inside the artic circle! Cant see how your engine coolant temp is going to get to -21'C and you completely loose battery voltage.
If it's an actual problem, it will come back.

[thenicolaibulow]

Hi ozvtr, thanks for chiming in!

The brake pedal data should come through the CAN BUS from the BSI. What is the BSI saying?

You should go into the actuator section of the "BSI" and "switch module behind the steering wheel" and check that all the switches are working.

If you see the attached screenshots, you'll notice that I did exactly this.

The brake switch has 2 sets of contacts. A normally open (NO) and normally closed (NC) set. The NO contacts are directly connected to the brake lights and monitored by the BSI. When the brake peddle is pressed these contacts close. The second set (NC) or "redundant" set, open when the brake peddle is pressed. They are also monitored by the BSI. This whole thing is to ensure that the brake switch is working correctly. Generally speaking, items on the CAN BUS only pay attention to the "redundant" set of contacts. It's not uncommon for these sets of contacts to malfunction. Automatic shifters "lock out" because of this problem.

Ah, thanks for this information - it definitely clears up the confusion I had about the two brake sensors. I could see how a defective sensor would be a deal-breaker for an automatic car
It sounds as though my redundant brake sensor might be dead then. The BSI's readout of the brake sensor never changes. Hell, I even had a little drive whilst live-monitoring the sensor readouts: Clutch switch works fine, brake sensors always register as 'Pressed'.
Is both the 'main brake' and 'redundant brake' sensors contained in the same unit? Seems likely as the sensor I can see has four, not two, wires leading to it. If so, I'll just go ahead and replace it!

My guess is that the engine ECU is not getting the correct brake switch settings and it doesn't like it. Undo all the bits that you have fiddled with and see if the engine ECU starts getting the brake peddle data.
Then add bits one at a time.

Yup - I'll give that a shot, although I would be surprised if the things I changed had anything to do with the brake sensor. I am also contemplating finding the wiring diagram for the brake sensor cable, and shorting out the appropriate pins, in an attempt to simulate a working sensor. - This would let me verify that it is in fact the sensor, and not a wiring issue.

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[thenicolaibulow]

I would clear the P1645 and see if it returns. It seems erroneous, unless you live inside the artic circle! Cant see how your engine coolant temp is going to get to -21'C and you completely loose battery voltage.
If it's an actual problem, it will come back.

Right?? Can we agree that these reading sound absolutely bogus? Can anyone verify if the battery voltage, and coolant temp, is stated as it was recorded when the fault happened? I mean, how would any part of electrical system be able to report anything, if the battery voltage was 0V - let alone the arctic temps.. Rest assured; it might get cold in Copenhagen, but -21° is undoubtedly a rare occasion - and I definitely wouldn't want to be caught out in it, let aloe try and start my diesel engine in it..

I should say that I did attempt to clear this fault - with no luck. Clearing faults with the ECU did clear two other accumulated EGR error codes (Known faults with the car), however this P1645 persisted, even after clearing errors out.

Thanks for the leads!

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[ozvtr]

If you see the attached screenshots, you'll notice that I did exactly this.

The screen shots (that I can see) are from the engine ECU (DV4). You have the BSI and COMs 'actuator' screens to look at too.

[ozvtr]

Is both the 'main brake' and 'redundant brake' sensors contained in the same unit?

Yes. The switch is located on top of the peddle box ON THE LH SIDE, behind the glove box on a RH drive car. It has a white connector and 4 wires. Edit: If you have a LH drive car, the switch is in the same place. But it would be above the brake peddle.
HOWEVER if the brake LIGHTS are working, then at least one set of contacts are working. From what I can see (and deduce) the switch is working but the engine ECU is NOT receiving that information. I don't know why!
Again, you need to look in the 'actuator' section of the BSI in LEXIA. To see if both contacts are registering in the BSI.
As I said, it's not uncommon for the secondary contacts to clag out because there is no 'wetting' current to keep the contacts clean. But the primary contacts remain serviceable because all the brake light current goes through them.

[thenicolaibulow]

If you see the attached screenshots, you'll notice that I did exactly this.

The screen shots (that I can see) are from the engine ECU (DV4). You have the BSI and COMs 'actuator' screens to look at too.

Oh! Of cause. I did not realise that I could read out the sensor information from several places. This is definitely worth looking into - I certainly hope that the BSI reads the sensor signal, the same way the ECU does. Can only imagine that it would be an outright PITA to try and debug, how the BSI en ECU would read this signal differently from one another. I'll definitely look into this.

Will report back with sensor readouts from both the COM and BSI.

[thenicolaibulow]

Is both the 'main brake' and 'redundant brake' sensors contained in the same unit?

Yes. The switch is located on top of the peddle box ON THE LH SIDE, behind the glove box on a RH drive car. It has a white connector and 4 wires. Edit: If you have a LH drive car, the switch is in the same place. But it would be above the brake peddle.
HOWEVER if the brake LIGHTS are working, then at least one set of contacts are working. From what I can see (and deduce) the switch is working but the engine ECU is NOT receiving that information. I don't know why!
Again, you need to look in the 'actuator' section of the BSI in LEXIA. To see if both contacts are registering in the BSI.
As I said, it's not uncommon for the secondary contacts to clag out because there is no 'wetting' current to keep the contacts clean. But the primary contacts remain serviceable because all the brake light current goes through them.

My car is LH drive, and I've definitely been able to reach the sensor, without too much hassle. I am, however, confused as to what I am seeing - you see, despite the four-wire brake pedal sensor, only two wires actually come out of the wiring harness. Plugged in between the brake sensor and the wiring harness, I've found a (to me) unknown 'adaptor', with a 2016 datestamp. It looks as though I might be a temperature sensor wrapped in with the wiring?

Looking up the P/N, it looks very similar, if not identical, to this

Whatever this might be, something doesn't add up:
Four wires coming out of the brake pedal sensor > adaptor / temp sensor thingy, with four cables > Two wires in the harness? As part of my debugging process I've unplugged / bypassed this 'adaptor' with seemingly no difference to the behaviour of the car (nor the ECU sensor readout).

I've ordered the full service manual for the car, hoping I'll get access to a full wiring diagram.

Can we agree that the sensor cabling should be braindead open/closed logic signals, and not CAN?

If the two wires I see from the wiring harness is CAN, I guess theoretically it could communicated both with a temp sensor, and two brake sensors, however I suspect that a manufactorer would NEVER let crucial signals, such as brake signals be run over CAN?

[thenicolaibulow]

Hi ozvtr,

Again, you need to look in the 'actuator' section of the BSI in LEXIA. To see if both contacts are registering in the BSI.
As I said, it's not uncommon for the secondary contacts to clag out because there is no 'wetting' current to keep the contacts clean. But the primary contacts remain serviceable because all the brake light current goes through them.

I think that you are on point with your diagnosis here.
The BSI is in fact reading the brake pedal sensor correctly!

I don't, however, see the 'redundant brake sensor' as an option to read in the BSI. Not that it really matters, I guess. The conclusion for now has to be that the ECU and BSI are not communicating properly, right?
Would you happen to know if they share the same wires, or if either the BSI or ECU gets the signal first, and then passes it on?
I'm guessing that the BSI has direct connection to the sensor wires, and is supposed to relay that information to the ECU?

[ozvtr]

When you go into the BSI in LEXIA, there is a sub menu labeled "actuator test" (or something like that). There you can monitor some switches including the brake switch. There is a similar menu in the "switching module under the steering wheel" ECU.
Are you saying that there are only 2 wires in that adapter harness? If so that will only be the brake light switch. No secondary contact info. I have a right hand drive C3 there is no adapter and the switch connector is white.

The brake switch is just a switch. It's connected to the BSI. The BSI sends information over the CAN BUS to the engine ECU. I am not sure but the BSI only monitors the connection to the brake lights. The secondary contacts of the brake switch are, IMHO, sent over the CAN BUS.

You may not believe this but my C3 is an auto, but up on the peddle box is a clutch switch!!! No clutch peddle but there IS a clutch switch!

[shtu]

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.

[thenicolaibulow]

Hi ozvtr, I really appreciate your reoccurring tips and thoughts!

When you go into the BSI in LEXIA, there is a sub menu labeled "actuator test" (or something like that). There you can monitor some switches including the brake switch. There is a similar menu in the "switching module under the steering wheel" ECU.

Exactly. I been able to verify the brake sensor readout, both from the BSI and ECU - although only the BSI is registering the sensor properly. The ECU sees both the 'redundant' and 'main' brake sensor as pressed.
I have not been able to find anything remotely brake-related in the 'switching module under the steering wheel' (COMs unit). I'm only able to verify readout from the steering wheel stalks, and various other interior buttons, from the COM unit - nothing related to brakes.

Are you saying that there are only 2 wires in that adapter harness? If so that will only be the brake light switch. No secondary contact info. I have a right hand drive C3 there is no adapter and the switch connector is white.

Yes! Much to my surprise! Every other mention i've found of this sensor (C3 or otherwise) states four conductors, not two
I'm waiting for my Haynes workshop manual to have a look at the wiring diagram. - Though.. would I be so lucky, that someone here could do me the favor of sharing the brake-sensor related diagram?
I'll have another look soon enough to try and trace the wiring back to wherever it branches off.

Hah! Just now I'm noticing that you have been commenting on the very post that i've been going off of, as reference. I can clearly see, from the pictures in post #4 - four wires to the brake sensor - where my car only has two! (Purple and white).

The brake switch is just a switch. It's connected to the BSI. The BSI sends information over the CAN BUS to the engine ECU. I am not sure but the BSI only monitors the connection to the brake lights. The secondary contacts of the brake switch are, IMHO, sent over the CAN BUS.

You may not believe this but my C3 is an auto, but up on the peddle box is a clutch switch!!! No clutch peddle but there IS a clutch switch!

I appreciate it. This is what I figured - BSI reads/monitors the signal, and controls the brake lights - whilst relaying it to the ECU over CAN.
I'm starting to suspect the CAN communication between the ECU and BSI. Would you know of any other sub-circuit that communicates this way? It would be nice to have a look at another sub-circuit to verify whether this CAN link between the two even works..!

Best,
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