Grand c4 Picasso B174E MotorisedTailgate fault code

[onthecut]

My new toy seems to have thrown up more glitches in six days than my faithful old 206SW did in six years !

The motorised tailgate was working when I collected the car but has now stopped. It still unlatches with the key fob, but does not motor up or down. The fault code reader is showing a code of B174E and a description of 'Motorised Tailgate Lock closing to second notch, status switch signal fault'.

What I can't work out is exactly where the status switch is located -- any offers, please ? I also notice the protective sleeve around the tailgate harness is split where it passes between the body and the tailgate.
Is this a precursor to internal breaks in the wires at this point ? As I recall, either the Xantia or XM estates were regular victims to failed wiring at this point.

Mike.

[GiveMeABreak]

Yes they were - it's the same with the doors - opening and closing weakening and breaking the wires over time.

I'll need the VIN if you want further help on the code (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).

[jlmj2009]

@onthecut Did you ever work out what the problems was? I've got the same fault code. I clear the codes but it comes back. I can use the diagnostic tool to close the boot if open, but it will not open from the fob or a button press.... The lock does work.

Only happened after disconnecting the battery after replacing an injector so Im a bit confused over the bad earth.

Some pointers would really help me to know where to start looking for the bad earth.

[GiveMeABreak]

@jlmj2009

When you disconncted the battery, did you follow the BSI Reset / Battery Disconnect / Reconnect Procedure? If not that can lead to problems.

Secondly how old is your car battery? If over 5 years, it probably needs a change. If the system detects a weak battery it may inhibit some electrical functions when the vehicle engine is not running.

The fact that it operated with the diagnostic means it's working, and the diagnostic tool temporarily overrode the energy management for testing purposes.

I'd certainly get your battery charged up and try it again once the vehicle has settled and the battery charge status has been recalibrated by the battery charge status unit.

[jlmj2009]

Hey @GiveMeABreak

I haven't done that BSI reset to be honest, I will give that a go! I had thought about it, but wasn't sure if that would help with the boot.

As for the battery. I've put it on a battery charger overnight but the issue remains the same in the morning. I'm using a CTEK MXS 10 which is usually very good. It's an AGM battery that was replaced about 18 months ago but I have noticed the car entering energy saving mode alot recently.

The boot only closes on the diag software but it will not open - Its reports a fault about the incorrect sequence or a fault (forget the exact error).

The boot does not open/close with the engine running either.

I didn't calibrate the battery when I fitted it, so I can try that also but the boot has been working fine until I disconnected the battery, so I'm not sure if calibrating will help.

Will post back if the BSI reset helps or not.

Appreciate your assistance!

[GiveMeABreak]

Do you have your VIN so I can check the correct battery type for your specific vehicle. 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. The reason being that if an AGM is not specified for the vehicle and you have fitted one, it can have an adverse effect over time as the vehicle's charging systems won't be geared towards charging an AGM type of battery. This can then affect the energy management of the vehicle. The battery should be of the same type and capacity as the original as that will have been configured in the BCSU.

[RichardW]

If the battery has been off then the BSI will have reset itself anyway. I've not investigated one of these, but it should be possible to see the status, and maybe do a reset, in Diagbox. Did you open or close the boot while the battery was off?

[jlmj2009]

@RichardW - OK, thanks for that. In Digibox, there are various tests to open / close / check the control unit. I tried them all. The only one that did something was the Close. When I test the Close of the boot, it works fine. If I try to Open the boot or test the Control unit, it fails with the error I mentioned earlier.

I've not tried the BSI reset, but the battery was disconnected for approx 24 hours. We didn't open/close the boot when the battery was disconnected. Sounds like I dont need to do that but at this stage I'll try anything.

@GiveMeABreak - The VIN is VF7**************[VIN obfuscated, can be read by forum staff]
Also, thanks for the advice on the battery. I've just checked and I fitted the battery in Sept 2021 - It's a 096 Enduroline AGM Stop Start Car Battery 12V 70Ah - Is it possible to change that in Digibox to an AGM battery? I dont know what was on it before, it was the original Citroen battery but the label was deteriorated and not readable.

In case it helps, all I hear are 3 quick beeps when I press the button on the boot or fob for both opening and closing the boot.

[GiveMeABreak]

Ok, so that's OK, as the original battery type is listed as an AGM and should be a minimum of 70AH 760A.

Ok, so ideally you need to have it scanned with Diagbox to see if there are any fault codes as there are quite a few associated with the system. This may give some pointers.

In the meanwhile. you can try reinitialising it by simply fully opening and closing the tailgate manually.

Also make sure the anti pinch sensor is not damaged and that there are no foreign objects pressing on it as this will prevent the tailgate closing:

[jlmj2009]

Thanks for your continued help @GiveMeABreak

Phew, something going my way this morning regards the battery!

I've scanned it with Digibox and I get the code B174E 11. >> https://photos.app.goo.gl/q9yQ7Ks1ozn2uCNV7

I've cleared the code but it comes back after a while and the boot still does not respond once the fault is cleared. There are lots of other previous faults stored on the car but I am apprehensive about clearing them all.

FYI - I've tried opening/closing manually several times. We've been using the boot in the traditional way but the motorised boot still doesn't kick in to life (FYI, start / stop is working, suggesting the battery is good/strong).

I'll check the anti-pinch sensor, I haven't checked that. But the fault code above does report a bad earth.

[GiveMeABreak]

Great, that's what we needed. So this is what the fault code states:

Fault Code:	B174E 11
Description of Fault:	Motorised tailgate lock closing to second notch status switch signal fault: Short circuit to earth. Short circuit to earth detected for 1s. Conditions of activation of the diagnostics: In all the operating situations.
Conditions for Fault to clear:	No faults for 1 second
Downgrade Modes whilst Fault is active:	De-initialisation of the motorised tailgate. Switching on of the warning lamp and/or warning message: Emission of a sound alert "Motorised tailgate fault or control not authorised" Door open warning lamp
Symptoms:	Malfunction of the motorised tailgate Message indicating that the motorised tailgate is open
Suspect Areas:	Electrical harness

So you have an earthing problem in the harness 'somewhere'.

My first suggestion is to check the area where the harness enters the tailgate. This is a common weak point that has constant pressure on the wiring, gradually weakening them as the tailgate is opened and closed. It's possible there is a break here.

I suggest you start here which is the earth to the Boot Manoeuvring unit:

MC63 is your earthing point - but the wire to it could be broken or partially broken anywhere before it.

[jlmj2009]

@GiveMeABreak - Thank you so much. It's been lovely all week in the south of the UK, but now we have rain. Once that's stopped I'll be tearing the boot apart to see if I can find the fault. Seems like the battery being disconnected was coincidental.

Thanks a million for all your help.

[Paul-R]

I would see if it's possible to run a (very) temporary earth lead from a good earth point on the car to the mechanism.

[jlmj2009]

Thanks Paul-R - Thats a good idea. Ill rip the boot apart and see if I can run an earth to rule that out. Appericate the pointers. Ill report back.

[Paul-R]

You could try using a single jump lead to various points.