At present we have ABS, BAS/ESP, brake warning, brake wear indicator, and rear spoiler flashing lights. Very illuminating but not funny. Also speedometer has stopped working but rev counter and other instruments are all fine. Heavy duty battery is new and fully charged. I fitted new discs and pads and a year ago. I have re-soldered suspect terminals in RCM and cleaned speed sensor rings on rear hubs. The sensor wires are sheathed in rubber at the wheel end and well enclosed at the under body end so nothing to wear or corrode there, by the way, why should these ever need replacing assuming they are undamaged? Main ground points have been checked cleaned and no rust. Brake stop light switch checked aok. I have read as many threads as I can find but can not find anything else to try that makes sense. The rear spoiler becoming u.s. happened first which I can live with, the other items all happened at the same time which would suggest a single electrical fault somewhere. The car drives well and has no adverse brake problems. There are no fault codes showing on my diagnostic device. Any reasonable suggestions would be greatly appreciated.

 

Possibly the conductor plate which has the 'speed sensor', or the transmission connector if this is an automatic transmission car.

 

Thanks for speedy response, the car has a manual gearbox so will look up the parts cat. to locate the conductor plate and speed sensor. I will let you know when a fault and solution has been found.

 

Curious, have you recently replaced a rear tail light bulb? I read somewhere a long time ago, that if the bulb is installed backwards, it could cause some lamps to light. Good luck finding your gremlin!

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The manual transmission has no conductor plate.

 

​​​​ you have a speed sensor problem. If your car was an automatic it would be in limp in mode right now stuck in second gear. You're going to have to get into the repair manual available here on the Forum and do your homework.

 

Agreed, that's why I mentioned the conductor plate, but the OP's is a 6 speed.
( I have no idea where the speed is measured in a 6 speed XF )

 

I'm searching the manual now. I have scanned the entire manual transmission section and there is no mention of a speed sensor. I suspect that the powertrain control module takes its information from the wheel sensors, I honestly believe that it's a matter of bad connection somewhere in one of the related components and possibly the fix could be as simple as disconnecting and reconnecting the major controlling electronic components, after disconnecting the battery ground cable first of course.

 

You are probably correct, I would think it would reference just one of the front ones ......

Probably have to put it up on jack stands and watch each signal at the CAB connector with a scope to see what the wave forms look like.

( Maybe 5 / 19 is the combined output signal ??? )

 

Yep it verifies in the speedometer section instrument cluster that the cab receives signals from the four wheel sensors

 

I revert back to my original thoughts I think a connector has lost continuity and it's just a matter of unplugging cleaning and reassembly and I believe that would fix the problem, the cab would be a good place to start and while you're at it I would do the same for body control module and powertrain control module. Be sure to disconnect the ground cable first.

 

Check out Section 8E page 92 very informative. I think the logical place to start is at the 4-wheel speed sensors, I think it would be a good idea to visually inspect each one disconnect each connector clean and reconnect then take it for a drive so that the system has time to reset itself if that doesn't work move on to each subsequent component in the system disconnecting and reconnecting.

 

longspoon, did you ever resolve your problem? I'm having all the exact problems on my 05 roadster, manual trans, 22,000 miles. I have the same warning lights. spoiler stuck in up position with the red light flashing on it's switch, speedo not working. This all happened last night at the same time. After I got home, I cut the car off and restarted it. It then had a check engine light added to the mix. After sitting all night, when I started it this morning, all the lights were gone and I was able to put the spoiler down with the switch. As I was going down the drive for a test drive, all the above happened again when I applied the brakes. This afternoon all the lights are still on when I start the car.

 

Dash lights, no speedo, spoiler in up position and no cruise control are still a problem. Biggest problem for me is getting time to work on these. So far I have re-soldered contacts in RCU plus cleaned contact surface of relays. Removed cleaned and replaced as many connection blocks and earth cables as I can find. Removed and cleaned all 4 speed sensors etc. The car drives perfectly with no adverse effects on ABS. I am waiting for new speed sensors to arrive and am about to remove the o/s front wheel hub where I suspect the problem lies. When I took the sensor cable away from there I noticed a slight rub mark on the pickup end, this usually indicates a cracked reluctor ring. You can sometimes see a bright spot on the ring where it comes into contact with the speed sensor when it is cracked. Over time rust on the hub surface creeps under the reluctor ring which is a shrink fit, expands and cracks the ring. I have tried to locate a supplier but so far only come up with someone who can supply a new hub c. $500 I also tried to find the measurements of the ring, again no luck. That is why I am removing the hub, to remove the old ring, to obtain the measurements and get new rings made. I can do this here in UK. Does anybody know if Merc SLK320 has same front hubs?

 

Yes it's the same.