General approach to repairs and diagnostics Diagbox question

Help with sourcing, buying, installing and using Lexia, Diagbox and OBD2 for a Citroen C3.
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Questions regarding installing and using Lexia, Diagbox or OBD2 for the Citroen C3

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My Name: jmmj

Contributor
Posts: 12
Joined: Sat Nov 21, 2020 6:09 am
Model: Other
Year: 2014 (14)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 37089
Trim Level: Exclusive
Gearbox: Automatic PRND
DPF: No
LHD or RHD: LHD
Engine name: TU5 16-valve (110 PS)
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Hi folks,

I have a 2013/14 C3 Aircross. We bought it with 20k km's on it. Its about 6/7 years old now and i've never really had to do anything to it until now - outside of oil changes of course!

Anyways, i bought a diagbox full chip latest firmware device. Got diagbox installed and everything works all fine, i can read /clear error codes etc.

1) Whats the 'work flow' for using the diagbox?? I've searched for tutorials and info on how the diagbox software is used and came up with very little. Now i've read a few things like, you should clear the codes, drive it, and see what comes back which indicates its not just a 1 in 10,000 km error. The thing is, i see i have some codes thrown with quite some frequency. Now the information offered in Diagbox is basically just the code with little or no indication of 'go change x part'...

For example, from several codes i know i have a dodgy brake switch. I also have an error code D308:

"Communication error between the automatic gearbox and the engine management"

Why is there no interpretation of what that could mean in terms of parts???? (i'm aware it might also be due to the brake switch)
Is a citroen specialist then supposed to consult some sort of table??

2) For some reason, i saw or just imagined that Diagbox would also include basically a service manual. For example, you need to adjust the valves. You look this up in the application and it gives you the procedure and the technical details like the gaps and torque values. When i click on "Documentation" within diagbox i get some sort of 'missing' error. Is there anyway to add this to diagbox or does anyone have a 'personal diagbox' that does have this info??

Cheers guys, any light on the topic will be much appreciated.

-Mike
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My Name: Ozvtr

Moderator
Posts: 1043
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 44 times
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Hi Jmmj and welcome to the forum.

Wow! Potentially I could have a massive tirade on this subject but I will save you the nausea. That doesn't mean this wont be long!!

Ok, depending how you want to look at things your car is about 4th generation, if you take the Saxo and its peers as the first generation.
I don't live in the UK and am not familiar, first hand, with the models and evolution of the C3.
My area of, shall we call it 'expertise', is the second generation (2003-2005) but I am quite familiar with the 3rd generation (2005-2009). I am also fairly familiar with the versions of LEXIA associated with those years.However from the 4th generation on it's getting a bit grey.

First up the software and LEXIA3 (hardware) that you are using are pirated!!!!!!
The software is designed to run as a satellite from a server (over the internet). On that server is the documentation and other stuff that you might be looking for. This is why you get an error when you click on the documentation button. BUT, not being a Peugeot/Citroen dealer you are NOT entitled to access to that server. Even worse, Manufacturers are now beginning to take the attitude that you are not even entitled to view their Intellectual Property I.E. service documentation! So we are left with the likes of Haynes to provide documentation. Their days may be numbered! Governments are now falling in line behind big business and failing to protect those who make a living repairing others products. If you pay and are entitled to the information Citroen will part with some of the information. But this is on a subscription basis. No pay, no access.

There are basically two forms of software for Peugeot/Citroen cars, Peugeot Planet (for Peugeot) and lexia (for Citroen). The "front end" for both of these is Diagbox (as you know).
There are two more forms of software that Peugeot/Citroen uses called SEDRE and Service Box.
Combined, the two have, service manuals, service history/schedules (and other logistics), fault diagnosis and the parts breakdowns. However they are designed to run on a server, not on a stand alone PC. Yes, there are pirated versions of those (out there) but harder to find and difficult to install on a PC.

There is a small diagnostic area in the LEXIA program. When you are in LEXIA and reading the fault codes, there is box down the bottom with diamond shape in it. This diamond represents the diagnostics flow diagram and if you hit the Function key (F3 I think) nominated in that box, it will give you some basic steps to try.

You must remember, this is professional software designed for professional technicians who have been trained to use this software. So help is going to be minimal.

LEXIA is only a tool, just like a spanner or screw driver. It must be used in conjunction with the users skill and knowledge.

The ECU's (the control boxes) have limited resources at their disposal. Typically it can tell you what's happening but it cant tell you WHY. For example, in your case, the engine ECU and the gearbox ECU are not talking. It doesn't know why, just the fact that they are not talking. As I said, IF there are some diagnostic hints for the user there will be a button down the bottom. There is not always that button there and sometime the diagnostic may specify use of a specialist piece of equipment that you may not have.

You are right, some of the fault code descriptions are vague at best but the user is supposed to have access to facilities that you don't. In fact, it is possible for the Citroen technicians to hook your car up to a LEXIA which is networked and have technicians at head office France (or whatever) tell the technician working on your car what to do. What chance do you have?

Like the ECU's, you have to muddle by with what you've got.

I'm sorry but the theory of fault diagnosis would take up pages and pages. Try searching for general car fault finding tutorials. Forget about the LEXIA specifically. Remember the LEXIA is only a tool. Use it to gather clues.

I have worked with ATE (automated test equipment) and I rarely find it works. They are designed by engineers who don't have to fix the pieces of faulty equipment. Engineers and technicians are mortal enemies, LOL! So if you think LEXIA is going to tell you what's wrong...well...no, not most of the time.

If you have any more questions...fire away I will try to help.
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My Name: C3CAR

Guru
Posts: 2658
Joined: Wed May 04, 2011 10:01 am
Model: C3 2002-2005, Original shape model
Year: 2002 (02)
Engine Size: 1.4 (16v)
Fuel Type: Diesel
Mileage: 140000
Trim Level: Exclusive
Gearbox: Manual 5 speed
DPF: No
LHD or RHD: RHD (UK)
Engine name: DV4 16-valve diesel (90 PS)
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1) Whats the 'work flow' for using the diagbox?? I
It all depends on what you want to achieve, from making changes to the configuration (e.g. adding keys) to diagnosing faults.


To fix faults:
Scan for errors from the main diagnostic screen,

Call up the fault and read it's description (in this case an intermittent faulty switch signal is reported)

lexia diagnostics
lexia diagnostics

From this you could use live data to monitor the signals that the ECU sees from the brake pedal and make a determination from the result of that.

You also have the option to press F5 (or click the button circled) to bring up the Citroen proposed solution (if there is one) and follow that too.
jmmj wrote: Sat Nov 21, 2020 6:46 am Now the information offered in Diagbox is basically just the code with little or no indication of 'go change x part'...
It doesn't work like that. The ECU doesn't know what part is faulty, other than the data it is presented with over the bus in not what is expected. It is the job of the technician to work out what is causing the fault.

For example, from several codes i know i have a dodgy brake switch. I also have an error code D308:

"Communication error between the automatic gearbox and the engine management"

Why is there no interpretation of what that could mean in terms of parts????
Well, it does.

"Communication error between the automatic gearbox and the engine management"

is telling you parts are the communication bus and its connections and the data on that bus associated with the engine management and the auto gearbox. It takes diagnosis by a tech to understand what is causing it. F5 may give you a list of checks to do. But, for example, if this only occurred once, when the car battery went flat, it won't be worth pursuing. It is a different fault if it is permanent and stopping the auto from changing gear.

When I am presented with multiple faults, I would check/test and fix the easy ones first , particularly if they could be linked (like a blown fuse). Then scan again to see if fixing one has had an effect on any other.
My Name: jmmj

Contributor
Posts: 12
Joined: Sat Nov 21, 2020 6:09 am
Model: Other
Year: 2014 (14)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 37089
Trim Level: Exclusive
Gearbox: Automatic PRND
DPF: No
LHD or RHD: LHD
Engine name: TU5 16-valve (110 PS)
Has thanked: 11 times
Been thanked: 1 time

Post

Ozvtr wrote: Sun Nov 22, 2020 11:10 am Hi Jmmj and welcome to the forum.

Wow! Potentially I could have a massive tirade on this subject but I will save you the nausea. That doesn't mean this wont be long!!

Ok, depending how you want to look at things your car is about 4th generation, if you take the Saxo and its peers as the first generation.
I don't live in the UK and am not familiar, first hand, with the models and evolution of the C3.
My area of, shall we call it 'expertise', is the second generation (2003-2005) but I am quite familiar with the 3rd generation (2005-2009). I am also fairly familiar with the versions of LEXIA associated with those years.However from the 4th generation on it's getting a bit grey.

First up the software and LEXIA3 (hardware) that you are using are pirated!!!!!!
The software is designed to run as a satellite from a server (over the internet). On that server is the documentation and other stuff that you might be looking for. This is why you get an error when you click on the documentation button. BUT, not being a Peugeot/Citroen dealer you are NOT entitled to access to that server. Even worse, Manufacturers are now beginning to take the attitude that you are not even entitled to view their Intellectual Property I.E. service documentation! So we are left with the likes of Haynes to provide documentation. Their days may be numbered! Governments are now falling in line behind big business and failing to protect those who make a living repairing others products. If you pay and are entitled to the information Citroen will part with some of the information. But this is on a subscription basis. No pay, no access.

There are basically two forms of software for Peugeot/Citroen cars, Peugeot Planet (for Peugeot) and lexia (for Citroen). The "front end" for both of these is Diagbox (as you know).
There are two more forms of software that Peugeot/Citroen uses called SEDRE and Service Box.
Combined, the two have, service manuals, service history/schedules (and other logistics), fault diagnosis and the parts breakdowns. However they are designed to run on a server, not on a stand alone PC. Yes, there are pirated versions of those (out there) but harder to find and difficult to install on a PC.

There is a small diagnostic area in the LEXIA program. When you are in LEXIA and reading the fault codes, there is box down the bottom with diamond shape in it. This diamond represents the diagnostics flow diagram and if you hit the Function key (F3 I think) nominated in that box, it will give you some basic steps to try.

You must remember, this is professional software designed for professional technicians who have been trained to use this software. So help is going to be minimal.

LEXIA is only a tool, just like a spanner or screw driver. It must be used in conjunction with the users skill and knowledge.

The ECU's (the control boxes) have limited resources at their disposal. Typically it can tell you what's happening but it cant tell you WHY. For example, in your case, the engine ECU and the gearbox ECU are not talking. It doesn't know why, just the fact that they are not talking. As I said, IF there are some diagnostic hints for the user there will be a button down the bottom. There is not always that button there and sometime the diagnostic may specify use of a specialist piece of equipment that you may not have.

You are right, some of the fault code descriptions are vague at best but the user is supposed to have access to facilities that you don't. In fact, it is possible for the Citroen technicians to hook your car up to a LEXIA which is networked and have technicians at head office France (or whatever) tell the technician working on your car what to do. What chance do you have?

Like the ECU's, you have to muddle by with what you've got.

I'm sorry but the theory of fault diagnosis would take up pages and pages. Try searching for general car fault finding tutorials. Forget about the LEXIA specifically. Remember the LEXIA is only a tool. Use it to gather clues.

I have worked with ATE (automated test equipment) and I rarely find it works. They are designed by engineers who don't have to fix the pieces of faulty equipment. Engineers and technicians are mortal enemies, LOL! So if you think LEXIA is going to tell you what's wrong...well...no, not most of the time.

If you have any more questions...fire away I will try to help.
Thanks for the thorough run down Ozvtr! Answered my questions and then some... Totally appreciate the time and effort that went into it. I know i'm new on this forum but i'd vote to sticky this, and the below reply, as a sticky for anyone thinking about the lexia device and diagbox software!

While realising our modern PSA cars are quite complex networks, I guess i thought the engineers would have taken steps by now to further 'fool proof' the role of the technicians!! But understanding how a technician works under the PSA banners helps immensely.

Anyone know if PSA training documentation is available somewhere on the interweb???

I'm a kiwi living in Brazil! I travelled all over South America (in a 2 cylinder 550cc L100 Mitsubishi mirco van) before settling down (i met a special lady). Always a pleasure coming across travelling Aussies and Britts, well, its always good times coming across other travellers, but its particularly pleasing coming across an Aussie and the associated banter!! :D

Sad to hear that Governments are falling behind car manufactures too, can't say i'm surprised. Governments don't represent us as citizens at all, its just an illusion of democracy (remembering that true democracy doesn't exist). Our Aircross, based on the c3 Picasso, will probably be the last 'modern' car that we own. I use a split window vw kombi for work, i have a vw bug to restore for the wife... along with some other 'oldies'. I still plan on adding a Citroen 2cv/3cv to the collection (already pre approved by the wife!) but we'll have to travel to Argentina to buy one as Brazil never had them.


Cheers!

-Mike
My Name: jmmj

Contributor
Posts: 12
Joined: Sat Nov 21, 2020 6:09 am
Model: Other
Year: 2014 (14)
Engine Size: 1.6 (16v)
Fuel Type: Petrol
Mileage: 37089
Trim Level: Exclusive
Gearbox: Automatic PRND
DPF: No
LHD or RHD: LHD
Engine name: TU5 16-valve (110 PS)
Has thanked: 11 times
Been thanked: 1 time

Post

C3CAR wrote: Sun Nov 22, 2020 4:07 pm
1) Whats the 'work flow' for using the diagbox?? I
It all depends on what you want to achieve, from making changes to the configuration (e.g. adding keys) to diagnosing faults.


To fix faults:
Scan for errors from the main diagnostic screen,

Call up the fault and read it's description (in this case an intermittent faulty switch signal is reported)


lexia-diagnostics.png


From this you could use live data to monitor the signals that the ECU sees from the brake pedal and make a determination from the result of that.

You also have the option to press F5 (or click the button circled) to bring up the Citroen proposed solution (if there is one) and follow that too.
jmmj wrote: Sat Nov 21, 2020 6:46 am Now the information offered in Diagbox is basically just the code with little or no indication of 'go change x part'...
It doesn't work like that. The ECU doesn't know what part is faulty, other than the data it is presented with over the bus in not what is expected. It is the job of the technician to work out what is causing the fault.

For example, from several codes i know i have a dodgy brake switch. I also have an error code D308:

"Communication error between the automatic gearbox and the engine management"

Why is there no interpretation of what that could mean in terms of parts????
Well, it does.

"Communication error between the automatic gearbox and the engine management"

is telling you parts are the communication bus and its connections and the data on that bus associated with the engine management and the auto gearbox. It takes diagnosis by a tech to understand what is causing it. F5 may give you a list of checks to do. But, for example, if this only occurred once, when the car battery went flat, it won't be worth pursuing. It is a different fault if it is permanent and stopping the auto from changing gear.

When I am presented with multiple faults, I would check/test and fix the easy ones first , particularly if they could be linked (like a blown fuse). Then scan again to see if fixing one has had an effect on any other.
Thanks for the write up C3Car!! Much appreciated. Diagbox is a whole other story when you know just a little more on what to look out for. I'll check out your tips... Thanks again.

Cheers!!

-Mike
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My Name: cfrank

Experienced Member
Posts: 48
Joined: Tue Jun 09, 2020 8:24 pm
Model: C3 2017-on. The new C3
Year: 2020 (70)
Engine Size: NA
Fuel Type: Diesel
Mileage: 1000
Trim Level: Feel
Gearbox: Manual 5 speed
DPF: Yes
LHD or RHD: LHD (Europe)
Engine name: BlueHDi (100 PS)
Location: Germany
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Excellent answers. Technicians' experience is always required.
To support them, car manufacturers provide guided diagnostics systems. These systems read diagnostic data and also ask the technicians to perform certain steps like revving the engine and then answer questions such as "did you see black smoke?" (just kidding but you get the idea).
Some years ago I was involved in the development of such a system - not for Citroen, though. Several companies worked together on a rather complex piece of software and it has cost millions of Euros. And that's "just" the software without the actual "knowledge". This was/is added later by "editors" - people writing guided instructions for workshop technicians. There is also a process to add new procedures if new problems are reported by a workshop. Now imagine the complexity of modern cars and the various model variants which all need to be covered. So maybe it's understandable why it's not always available for free.
User avatar
My Name: Ozvtr

Moderator
Posts: 1043
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 44 times
Been thanked: 300 times

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Hi Mike
I don’t want to be a party pooper but I have to put my moderator hat on and ask you to split this up into more posts?
Can you put a quick introduction to yourself in ‘The Citroen C3 club’ area (and we’ll talk about old cars, jandels and free turns LOL) and add a post to the ‘questions about an automatic’ (and we’ll try and help you with that one) please.
This post is fine and we will continue on topic Re: LEXIA, Diagbox and fault finding.
No offence intended but posts can tend to ramble on and go off topic.
User avatar
My Name: Ozvtr

Moderator
Posts: 1043
Joined: Wed Jul 10, 2019 3:31 am
Model: C3 2002-2005, Original shape model
Year: 2003 (53)
Engine Size: 1.4 (8v)
Fuel Type: Petrol
Mileage: 80000
Trim Level: Other
Gearbox: Automatic PRND
DPF: No
LHD or RHD: RHD
Engine name: TU3 (75 PS)
Location: Brisbane, Australia.
Has thanked: 44 times
Been thanked: 300 times

Post

The hardest thing with LEXIA is getting the software and hardware working. If you have managed to do that you are well on your way.

My first LEXIA had a fault in the hardware, so I had no idea what was going on until I got new hardware that was working. The first LEXIA would only read the engine ECU and gearbox ECU. The Forums confused me by saying things like “add or subtract the ‘0’ from the beginning of the RPO number”. Not helpful! I still have to find the fault in my first LEXIA. I have replaced a few chips in it but so far no joy.
As I said LEXIA is a tool and will provide clues to faults. It may even tell you the answer to some faults. It’s not the be-all-and-end-all BUT it is a very powerful tool and one you should definitely have!
The hardest thing with fault diagnosis is how things work in the first place. As I said that tends to be a closely guarded secret by the manufactures but forums like ours might give you some clues.
The design philosophy of the Americans, Japanese and Europeans can be very different. For example, the Japanese tend to modularize their electronics making ECU’s independent to do their own thing but the Europeans tend to integrate their electronics such that most, if not all the ECU’s, talk to each other. As an example the ABS ECU talks to the radio to tell it how fast the car is going so that the radio can turn the volume up! A consequence is that removing the radio results in the central locking not working!!!!!WTF?

My point is; thinking that a system should work a certain way is fraught with danger. So it’s a slow and steep learning curve.

The most powerful part of LEXIA is the ability to read, monitor and clear parameters that a plain OBD reader can’t. Some of the more powerful code readers can do it but at a much greater cost. Unfortunately even the LEXIA can’t read everything and there may still be gaps in the information. For example, the engine ECU monitors the ‘high side’ pressure of the air conditioning refrigerant lines. However LEXIA cant get that information from the engine ECU! In fact there is only one parameter in the whole air con system that is monitored and that is the status indicator in the engine ECU. This reads ‘inhibited’ or ‘active’. Not very helpful. HOWEVER, you CAN engage the compressor clutch and you CAN engage the thermo fan. So you sort of need to think laterally when it comes to dealing with a computer.
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