Fault code diagnostics.....

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XMplory
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Joined: 13 Feb 2005, 10:01
Location: United Kingdom
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Fault code diagnostics.....

Post by XMplory »

I have just been reading this from a BX diy site.....
"When the EMS warning light (symbolizing a transistor, similar to a letter K) lights up on the instrument panel, don't wait too long. Unless the failure is permanent, after twenty engine starts the fault flag will be automatically cleared. Not all errors that store an error code in the computer will light up the warning light, less serious and passing errors do not.

The fault codes are easily retrieved by a Fault Code Reader, a special diagnostic equipment. At least they are supposed to be special but it is very easy to rig such an equipment. First of all, <font color="red"></font id="red">many systems<font color="red"></font id="red"> only need a single switch to operate the diagnostic readout, the codes will be displayed using the mentioned warning light on the dashboard. Some other systems will use a LED in the diagnostic equipment itself (you might prefer this solution even if your system can use the dashboard lamp as this spares you the trouble of finding a long wire so that you can sit back behind the steering wheel to see the lamp). The circuit diagram shows how utterly simple such a "specialized diagnostic equipment" looks like.
Once you have the reader connected to the green Self Diagnosis plug and the ground, switch on the ignition. Close the switch for three seconds (the LED or the dashboard lamp should stay off), then open it. The LED will flash n times, then pause for 1.5 seconds, then flash m times. The code the system tries to tell you is 10n+m. Wait three seconds before you repeat the procedure.
The first code you receive will be 12, meaning Test Start. The last one will be 11, Test End. If there are no other codes between these two, the ECU has nothing to say. Otherwise, check the meaning of the codes in the following table (not all code numbers can appear on all systems):"
Code Failure at...
11 Test End
12 Test Start
13 Air temperature sensor
14 Coolant temperature sensor
15 Fuel pump relay feed
21 Throttle switch, idle contact
22 Idle speed control valve/motor feed
23 Idle speed control valve/motor
25 Variable inlet resonance L valve
26 Variable inlet resonance C valve
27 Vehicle speed sensor
31, 32 Wrong fuel/air mixture
33 Air flow or MAP sensor
Throttle potentiometer (Mono-Jetronic)
34 Canister purge electrovalve
35 Throttle switch, full load contact
36 Oxygen sensor heating
41 Crank angle sensor
42 Injector
Code Failure at...
43 Anti-knock control
44 Knock sensor #1
45 Ignition coil #1
46 Turbo pressure valve
47 Turbo pressure regulator
51 Oxygen sensor #1
52 Oxygen sensor system control
53 Battery voltage
54 ECU
55 CO mixture potentiometer
56 Coded alarm system
57 Ignition coil #2
62 Knock sensor #2
63 Oxygen sensor #2
64 Fuel/air mixture control B
65 Cylinder sensor
71-76 Injector #1-#6
91 Injectors feed

On the site http://www.tramontana.co.hu/citroen/fuel/test.html it also shows a small diagram of how to make a fault code reader out of a switch and an LED etc.
Can i not do this on my XM as i'm sure it has the same 2 pin diag socket as described above and has this older type engine management/fuel injection system as used on BX injection engines ?
Or could i just 'jump' the two diag socket wires and read the code of the dash ?
Anyone done the above proceedure on thier Citroen successfully ?
p.s anyone got a spare XM ECU in case i f##k it up ![;)]
XMplory
Posts: 12
Joined: 13 Feb 2005, 10:01
Location: United Kingdom
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Post by XMplory »

BTTT ?
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AndersDK
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Location: Denmark
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Post by AndersDK »

Try it out with that code reader !
It works on all later BX's and can NOT damage the ECU.
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