XU10J2 crankshaft position sensor ?

Mosser · Post by **Mosser** » 03 Mar 2007, 16:23

No luck finding the relay, it shows their positions in the cars manual, but only lists the fuses and what they are for, and theres quite a lot of relays behind the glovebox and in a box under the bonnet,

More searching the web for me then !!, but i feel like i am getting much closer to fixing the fault now though

Mosser · Post by **Mosser** » 03 Mar 2007, 17:16

Found it, its another little black box made by Bitron with the part number 240107 on the top, and it shows a little circuit diagram on the top of the box thats exactly the same as the circuit diagram on the pug forum

Now i've just got to do some tests on it and maybe replace it if needed

Mosser · Post by **Mosser** » 05 Mar 2007, 14:12

Its probably a long shot, and i've probably used up everyones information on my electrical system !!, But does anyone know what sensor inputs and conditions need to be met for the ECU to ground the relay input to the multi function injector/ignition relay ?

If i ground the multi relay myself, the fuel pump springs into life along with it powering the coil on the correct pin at the same time, but the engine still refuses to start as the ecu doesnt send an appropriate signal to fire the coil at the correct time, So i am guessing that either the ECU is waiting for an appropriate signal from another sensor input before it latches the fuel/ignition relay, OR the ECU is knackered and not actually running !

If anyone knows any links to sites that detail the Magneti Marelli ECU system and how it works, i'd appreciate it

I am an electronics engineer with previous experience of reflow repair work on pcb's, so fixing the ecu if it has failed shouldnt be difficult, but i am stumped without more information on how the Magnetti marelli system works, and under what conditions it will energise the ignition/fuel relay

Thanks again!

Post by **CitroJim** » 05 Mar 2007, 14:53

Hi Mosser,

A very quick answer just before I give blood...

I think the ECU has to be unlocked by the immobiliser and have switched ignition applied. Then it'll operate the double relay ready for a start.

I'll do a bit more research later...

AndersDK · Post by **AndersDK** » 05 Mar 2007, 15:08

Well, another one of those Elektor subscribers I guess

You are back on the TDC sensor then

This is THE one sensor that tells the ECU that the engine is running (or cranking by the starter).
The ECU has a built in timer in the software, letting the fuel pump intially running for 1.5 second, to pressurise the throttle body.
Once the starter is commanded to crank engine, the fuel relay is also energised.
Meaning : if you stop cranking the engine by the key, and the engine does not run, the relay immediately de-energises.
Only consequence if you manually keeps the relay energised by strapping it, is loading the battery and keep the fuel pressure up (fire hazard !)

This knowledge should be on your backbone fault tracing any petrol non-starter of recent era.

Note that most documentation available refers to the TDC sensor as a "Hall" sensor. This should be interpreted as a magnetic sensitive sensor in its widest meaning, as it is simply a wirewound pickup coil sensor. No built-in amp or output driver, just a simple coil.
The coil sensor would have any ohmic resistance in the 100-600 ohm's range, depending on exact type. Any high impedant reading is a NO-GO. By nature they have a habit of disrupting themselves by thermal cycle stress over the years.

Hopes this brings you just a wee bit back on track ...

PS : The good ole BX DIY site contains VERY extensive descriptions of engine management system components - and fault tracing :
http://www.tramontana.co.hu/citroen/
It is well worth the time spent reading 8)

Post by **CitroJim** » 05 Mar 2007, 16:46

Anders, I think the double relay operates before the crank sensor does anything. First thing my injection cars do is to spin the fuel pump when the key is turned even before the engine cranks.

The fuel pump not priming is the primary thing to lok at...

Elektor magazine. Now that brings back memories to this old electronics engineer!! Not sen a copy now for years and years...

Mosser · Post by **Mosser** » 05 Mar 2007, 17:03

Thanks, Lots of info to digest and look into there !, I will read though the BX site and see what they have on there, but the ecu doesnt prime the fuel pump on turning the key, and there is no information on the immobiliser on the circuit diagrams that i have !!,

Do you know if the ECU does its own decoding of the immobiliser chip ?, or does an external box do it then send a go signal to the ecu ?

AndersDK · Post by **AndersDK** » 05 Mar 2007, 17:51

http://www.elektor-electronics.co.uk/

The ECU should definately prime the fuel pump by energising the relay before the engine is cranked. You can usually hear the faint 1.5s buzzing from the pump, at the instant you turn the ignition key on.
When the engine is cranking the relay should again be energised.
These 2 conditions should be rather easy to test : simply connect a testlamp parallel to the relay coil - or the pump feed.

Only if the TDC sensor is providing an engine running signal, the relay will stay energised when starter has finished cranking.

The ECU is not a rocket science lump. Worst part would be any thick layer of weather protective covering over the circuit board & components.
Most likely its a common corrosion problem in the external multiconnectior - on some of the pins.
Any dry soldering joint is heard of as a known failure as well as burnt out ground copper trcaks and burnt out power drive transistors (Pwr fets).

Post by **CitroJim** » 05 Mar 2007, 18:57

Rito,

Blood given, one empty arm but otherwise OK.

It is so true Anders that even in these high-tech times, 90% of electronic faults are still caused by the same old things, bad connections, dry joints high wattage resistors, power semiconductors and of course electrolytic capacitors! Quite reassuring really.

Onto the ECU, studying the diagram I have, 8200 is the coded keypad and this superficially does little more than operate relay 8204 to apply 12V to ECU pin 35. That must be the initial 12v feed to the ECU and then one set of contacts on the double relay 1304 holds 12V on pin 35 even if the keypad is disconnected whilst the engine is running. hence why the keypad can be disconnectd on a running egine.

Mosser, I'm assuming that you've checked all fuses and wiring in the fuseboxes. The keypad also sems to put a condition on pins 10 and 15 of the ECU too. I think these may be some sort of data lines to lock/unlock the ECU as I doubt just operating relay 8204 will be enough on its own. It is worth checking to see if the keypad is workings as normal and is firmly connected to the ECU. Relay 8204 could be the problem though as this appears to "kick" everything off.

Does the "K" light come on when the ignition is switched on Mosser? If it does this shows at least the ECU is getting some voltage.

Check the main ECU earth on pins 34 and 17 too. If this is suspect nothing will work.

The outputs from the ECU to operate the double realy are open collector so pins 7 and 10 of the double relay need to go to 0V to operate the coils. Unoperated, you'll see 12v on these pins. Check that both relay coils are good and that the connections between the relay and the ECU are good as the ECU may well "look" for 12V at pins 23 and 4 to ensure the double relay is there and in circuit.

The TDC sensor will be 1620 on the diagram. It is called the speed sensor. It looks like its an inductive component so should be testable with an ohmmeter. If it shows some resistance, say between 100 and 1K ohms then it is most likely OK.

Oh for a circuit diagram of the ECU itself. It wold take away a lot of guesswork here.

Anders, can you add to this at all please? I'm feeling I may have missed something but being a pint of blood down my thinking may not be good!!!

Post by **CitroJim** » 05 Mar 2007, 19:04

Just another thought,

Looking at the circuit, if the inertia switch has operated accidentially (1203 on the diagram) this looks as if it will kill everything...

Mosser · Post by **Mosser** » 05 Mar 2007, 20:33

Blimey !, between you two, you are comming up with ideas faster than i can test them !!

Thanks for the input though, its much appreciated, I owe you some beers when you are next down Warminster in Wiltshire way !!

I just tested the TDC sensor and it has 360 ohms on it, so that looks fine, and i have hotwired and simulated ECU grounding through the ignition/fuel pump relay and it did what it should have done,, so thats ruled out of the equation too, the coilpack checked out fine between the windings as well so that can be ruled out too, and now i have checked power through the fuel cutout switch when the ign/fuel relay is hot wired and that is working perfectly too so thats ruled out

Here's whats been tested so far and is known to be good and working

1, TDC Sensor
2, IGN/Fuel pump double relay
3, Coilpack
4, Fuel cutoff switch
5, Ignition switch
6, battery is fine

Mosser · Post by **Mosser** » 05 Mar 2007, 20:44

part 2 of my reply!!

Not sure what a K light is ?, if its the engine light, then it doesnt come on, and i've never before seen it on so the bulb might be blown ?

There is no coded keypad on my car, it was never there and has worked perfectly for the last 2 years for me

All fuses have been checked and buzz through, I checked the wiring on the back of the fusebox under the bonnet, but not the wiring on the back on the behind the glovebox fusebox, as it looks like the dash has to come out to get at it

Main ECU earth hasnt been checked as i cannot find any pinouts for the ECU connector, they arent marked on the inside or outsides of either half, But i have ran and extra ground wire from the ECU case to the battery negative as i'm assuming that the pcb will be grounded to the metal case its in ?

Mosser · Post by **Mosser** » 05 Mar 2007, 21:20

This is the book i need !!, It covers the Magneti Marelli 8P ECU in depth apparently including diagnosing faults

http://cgi.ebay.co.uk/Engine-Management ... dZViewItem

I will be down my local motor factors looking for this one in the morning

Post by **CitroJim** » 06 Mar 2007, 12:13

Any news Mosser?

This is a strange one. It looks like the ECU itself but they're so reliable these days it is highly unlikely.

It'll be something simple. It always is when things get this deep

Keep us updated

Mosser · Post by **Mosser** » 06 Mar 2007, 12:29

afraid there has been no progress today, i do think that it is either ECU faliure, or the immobiliser that is stopping it working, but there is so little info ont he immobiliser than i dont know how to test it or check that it is at fault, I would have at least expected a light on the dashboard to indicate that the immobiliser isnt working, but there's nothing

I rolled the car right back down my drive so that the engine and ecu are in the sun and have taken the bung out of the back of the ecu in case its damp inside, but it didnt appear to be, and all the contacts and tracks are bright and shiney, so no corrosion inside, but the main chip looks like a 27c512 and i have a chip programmer so i might pull the chip and download its program and have a look at what its doing, I even have in circuit emulation hardware, but not too sure how this would help me and what it would prove really as i think its a hardware faliure rather than a software failure

Not sure what to do next now though, drawing a blank on ideas !, but i wont give up on it