Diagnostic Tool

[Citroenfan]

Out of curiosity - what is the best diagnostic tool for an Series 1 (1990) V6 XM?

TIA

Steve Hammond

[xmexclusive]

All XM's have diagnostic plug in points for ECU's.
On Mk2 XM's these are wired into the car loom and taken to a 30 pin socket under the dash.
On Mk1 XM's each ECU has a diagnostic socket on the end of a short lead.
A full Lexia 3 kit comes with both types of plug.

No other commercial code reader comes close to replacing a Citroen Lexia

Genuine Citroen Lexias or earlier variants are hard to find.
Not all the Chinese clone Lexias are equal in quality or complete with all leads.
Nor does price ensure quality.

Before you start the Lexia search read Noz's XM ECU fault finding guide in the self help section.
This includes details of a simple "blink code" circuit to use to read and reset individual ECU's.
For the price of a LED and a resistor you can read all your ECU faults.

John

[Citroenfan]

Thanks for the info - However I could not find a link to the file in the section you mentioned. I did, however, find it on the Yahoo XM-L list as was mentioned as another possible source.

Steve

[xmexclusive]

Hi Steve

Title is:

Ecu Error Code Reader And Codes, for common XM ecu's.
Post started Jun 14, 2006.

John

[Citroenfan]

Hi John,

Got the reader and all was working just fine until today. The hydraulic pressure warning light started coming on a few days ago when the brakes are applied. Turns off a few seconds after the brake pedal is released. I suspect the brake accumulator may be weak or gone. However, I went to pull the codes (been a while since I have done that) and the little diode based reader no longer functions. Connect up black wire to battery ground. the red wires into the cig lighter socket. Red LED comes on. Turn on ignition, hold down interrupt switch for 4 seconds and nothing.

Any ideas ?

Steve

[xmexclusive]

Hi Steve

Not sure what has gone wrong with the blink code reader, sorry.

As for your hydraulic light:
I would be checking out the return feed from the Brake Valve.
My guess is that there is now significant internal leakage in the valve.
As all returns run separately to the LHM header tank it is visually possible to check.
Get someone to hold the brake pedal down and inspect the return volumes at the tank.
Somewhere there is a diagram of the return pipes.
I will see if I can find a link.
Brake valve (Doseur valve) is directly behind the brake pedal on LHD XM's.
Found in the scuttle below the windscreen on RHD.
Valves are the same in both cases RHD just uses extra rods and cranks because of location.
These valves are common to all XM's and fairly easy to overhaul.
Kits for "O" rings and rubber end caps can be found on ebay for about £10.

My logic here is that low pressure only occurs when brake pressure is applied.
It quickly returns to normal on brake release.
Low pressure due to weak pump or other (suspension & steering) should not show only on brake application.
It could be though that there is general leakage beyond normal.
As a result brake demand for LHM is the final straw that leaks too much.
The pipe return check should confirm which hydraulic circuit section(s) are leaking.
Making the checks with and without brake application should show how the return leakage changes.

Best regards

John

This post has been edited by xmexclusive on December 02, 2016 12:04 pm

[xmexclusive]

Some information as promised.

This post has been edited by xmexclusive on December 02, 2016 12:21 pm

[xmexclusive]

Do not seem to have worked out how to add more than one scan to each post.
So there will be a series here for now.

[xmexclusive]

And another.

[xmexclusive]

Source of these documents:
Some of the books can be found second hand on ebay.
The final one is still in print and available new.

[xmexclusive]

second book.

[xmexclusive]

Final one.

[Citroenfan]

Hi John,

Thanks for the info and diagrams. I did 'score' a complete set of factory workshop manuals for Series 1 cars some time back. Will look into that return line a bit later when I have more time.

Take care,

Steve