fault reading ECU

Unread post by **504** » 19 Dec 2006, 11:54

Hi

does anybody have the routine for fault reading the codes on a 205 XU5 engine with Magneti Marelli ECU. I've tried one routine on AussieFrogs but it didnt work. Thanks.

pugxpert · Unread post by **pugxpert** » 19 Dec 2006, 19:34

earth pin on 2 pin diagnostic socket with ignition on for 3 seconds then observe engine warning light should flash once then a pause then twice this is 12 start of sequence then earth wire for another 3 seconds then will flash (for example) 3times then pause then 4times this is code 34 then earth again for another 3 seconds keep repeating this procedure untill you get code 11 which is end of sequence.. do a search on google for fault codes and this will tell you what each no means.

Unread post by **504** » 20 Dec 2006, 00:46

yeah this is what I did last time and nothing happened. The diagnostic socket is the green one by the master cylinder, not being thick am I? it has two female pins. Tried it on both earthing to the body, nothing happened!

AndersDK · Unread post by **AndersDK** » 20 Dec 2006, 13:51

Info for the BX with MM EMS on the same engine is found here :
http://www.tramontana.co.hu/citroen/
In general you can take advantage of anything engine related on that homepage

I would think that your diagnostic connector has converted its copper wires to something resembling green/black dirt - not able to carry much more than a few pico ampere

Unread post by **504** » 02 Jan 2007, 13:42

still no joy getting the ECU to flash the codes up for my 205 Automatic. It still runs just fine. The last instance of the fault light coming on (after the last reset amd several weeks of motoring), was a motorway run after about 40 miles setting off from cold, gentle warm up for 4 miles then up to 70+ running.

I read that the coolant temp sendor is often a culprit so found what I think is it on the back of the cylinder head. However there are three connections here.

The top left in the picture is what I think is the coolant temp sender ? if so what are the others?

Using a multimeter to test the resistance the other sensors seemed to read 0.4 however what I think is the temp sendor didnt give a reading, so I think this is the one, can anybody confirm this as I don't know much about this.

thanks!

pugxpert · Unread post by **pugxpert** » 02 Jan 2007, 21:19

top left i think is gauge middle lower is engine ecu coolant temp right (red) engine overheat warning lamp, i would check oxygen sensor they used to fail quite regular on the auto also check for water or moisture in connectors for o2 sensor bllue and black or red and white depending on year

Unread post by **504** » 02 Jan 2007, 23:22

Thanks for the reply. The car had a new lamdba sensor in June as it failed the mot according to the paperwork, would it fail already?

If the temp sender is the middle lower that looks a two pin one, what should I try and meter read it as?

pugxpert · Unread post by **pugxpert** » 03 Jan 2007, 20:10

could have failed again,not too sure of resistance without looking it up could put volt meter on supply wire and watch voltage drop as engine warms up think will start about 2.5/3.0 vlots down to about .5 volt when warm

AndersDK · Unread post by **AndersDK** » 03 Jan 2007, 21:59

The coolant temp sensor CTS is the 2pin type of the 3 sensors in that area.
Its a PTC generic resistor type sensor. Ranging from some 5K ohm (hi-resistance) at cold - down to some 500 ohm (lo-resistance) when hot.
The actual resistance in ohms is not that important, so you wont gain anything knowing if it is 3467 ohm or 2718 ohm at cold.
Its the large shift in resistance over the temp range that is important.

If the sensor fails, it usually disrupts completely (i.e. mega-ohms). Watch out for corroded connector or cabling. This resembles a cold engine and the ECU will then keep choking the engine.

NOTE : If there is an engine management fault lamp present, then you also have the fault code readout option.
I suspect you either have a defective (rotten) diagnostic connector cable, or not yet have found the correct initialisation method.

Unread post by **504** » 04 Jan 2007, 17:56

Well found the blue and black connectors under the expansion bottle, and gave them a clean. The heater plug did have some corrosion on the terminals.

Left the battery off for 1/2 hour and connected the light was still on, 100 meters down the road out it went, so took for a 20 mile drive and its stayed off ... watch this space.....