Yes, that is correct.
Yes, if memory serves, there should be battery voltage to F1.
I have an S-Type here, so I'll check it and see what the voltage is to F1 in both ignition switch positions 2 and 3.

 

Thanks NBCat for your answer.

@Karl: I put 12V on F1 and it cranks and start.

Well, good news but I still does not understand. If 12V is supposed to be on F1 as soon as the key is in RUN mode, why putting 12V in this mode permit the engine to crank ? When does the ECM put the starter relay to ground ?

 

The F1 fuse is energised through the gearbox neutral switch/transmission range sensor. So that appears to be the next thing to check as it will only provide 12v to F1 when the gearbox is in 'P' or 'N' positions.

 

Sorry, but am working off the top of my head at the moment. I don’t have computer access right now to see the full wiring diagram.

IIRC, fuse F1 is kind of an oddball. It’s not a power supply as most fuses are configured, such as where power from the battery branches off into multiple circuits. F1 is a solitary inline fuse between the ignition switch and the start relay. It only has power when the key is held to the spring-loaded start position. At all other times there is no power at F1.

This same fuse also supplies a “start request” signal to the ECM with the key held to the start position. The ECM takes this input and then provides the ground for the start relay to energize.

So the ignition switch and F1 together send power directly to socket #1 at the start relay. At the same time, the switch and fuse also send an indirect signal (via the ECM) for a ground at relay socket #2.

 

On the pre-facelift X200 I have, F1 has power when the ignition switch is in position 3 (engage starter motor). I'm assuming a MY 2003 must be the same.

 

Here is the Electrical Guide for an early vehicle, which should have the same basic circuits as the facelift cars.

Section 02 on page 89 shows the starter motor circuit.

 

Note the earth side of the starter relay coil is through the instrument pack.

 

Thank you again Karl and NBCat.

So if I understand well, F1 is connected to the ignition switch. If I have no current when the key is in START position, there is a broken wire between the ignition switch and F1. I will begin by disconnecting FC37 on the fuse box and check on pin 3 if there is current in START position. If yes, the problem is inside the fuse box, otherwise it's between the ignition switch and the connector.

Do you know the cable path between the ignition switch and the fuse box ? How can I find it ? on the wiring diagram, it's named WB. Does it mean W(hite) B(lue) ?

 

I'm using the wiring diagram I attached to this post, page 49 which is different.

Laurent

 

The fault may be the electrical part of the ignition switch not allowing power to come to F1. If you provide 12v to F1 and the starter motor engages, then the earth side of the circuit is most likely functioning correctly.

 

Just in case the problem lies with the ignition switch, here is one available from SNG Barratt France:

https://www.sngbarratt.com/English/#...&saveBranch=FR

 

Thanks NBCat. So when I provide 12v to F1, the starter engages and the engine starts. So as you said, the earth side is good.

Concerning the ignition switch, I think it works because when I read the data stream on the can bus of the instrument cluster, when I switch to START, the value "Ignition crank switch" switches from NO to YES.

 

Working from several thousands miles away, that does seem to be the most likely culprit. The other possibility (less likely) is a broken wire between the switch and F1.

It would appear battery power is reaching the ignition switch (FC18-4), via the "7" inside a box on the diagram. Look at wire WG from the switch, at contact FC18-7. That leads to a figure 01.5, which powers multiple circuits like the fuel pump. Since the fuel pump is obviously working, that means power is reaching the switch. Your mission, should you choose to accept (sorry for the 1960's US TV reference) is to figure out why power is not getting from there to F1. The switch itself is more likely, as it is a moving part, but the fault could also be a broken wire.

Sounds like you will have to access the connector on the switch. From there, you can check continuity between FC18-4 (power in) and FC18-1 (start signal to fuse F1) when the key is held all the way over to start. You can also test for a broken wire by checking continuity between FC18-1 and fuse F1.

As far as why the problem suddenly appeared out of nowhere? Who knows, but parts do fail. Years ago, I had an ignition switch fail out of the blue, leaving me stranded at a restaurant. These things do happen.

The only other thing that comes to mind is to make sure the fuse panel sockets for F1 are good and tight. Cut a spare fuse in half, so it only has one prong. Make sure this single prong fits tightly into both sockets. It's important to test the sockets individually, because if only one is loose and you are testing both at the same time with a whole fuse, you might miss it.

 

If there is a signal on the Can Bus, then I would expect there should be a corroded or broken connection in the WB (White/Black) wiring between switch and F1 in the footwell.

The easiest place to start is to see if the connector at the ignition switch has power to the WB wire when it leaves the switch. That would also confirm the switch is functioning correctly.

 

Be careful. One possibility is dirty contacts inside the switch, or multiple broken strands within a wire run. Whatever the restriction, it may let a tiny amount of current through to allow the computer to see it. However, the electromagnet inside the start relay draws a medium amount of current, and not enough juice gets through. This is a very common trap during electrical troubleshooting, where a meter will show voltage when the circuit is unloaded, but there's not enough oomph to power the circuit under load.

 

Hi folks,

so today I began by disassembling the steering column carters to access to the ignition switch. I tested it and it works:
- there is 12v on the pin1 when in position III;
- there is no resistance (0 ohm) between pin 4 (12v from battery) and pin 1.

After that, I tested the continuity between the ignition switch pin 1 and the fuse 1. No continuity. I removes the FC37 connector (which is plugged on the primary junction fusebox) to check the continuity between the ignition switch and the FC37-3 pin. No continuity.

Conclusion: the wire BW between the ignition switch-1 and the FC37-3 pin is broken. Well. And now ? I figured out two solution:
-1- search for the discontinuity;
-2- put a new cable.

The solution 2 is simpler but I wonder why this wire is broken. I mean if this one is broken, may by some other in the same electrical harness are broken too. What would you do if you were me ? For the solution 1-, do you know the electrical harness path ? I changed the gear selector some days ago and to perform that, I had to remove the GPS screen. Do you think this wire is behind this screen and I pinched it ?

Thanks again,

Laurent

 

Hello,

I put a new wire between ignition-1 and fc37-3. The engine now cranks well and starts !

Thanks all !

Laurent