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Full Version Re:erratic Rev Counter

Club XM Forum > XM General Issues
My car has been laid up for a couple of months and now the rev counter flicks 2-3000 RPM higher before returning back to normal.Sometimes it does it,sometimes it doesn't!Any ideas?
Also I saw somebody had downloaded a picture above the signature(presumably of their car).How do you do this as I have looked but can't find a link to do it.Also how do you change your user name as I have never liked Little and large...but it seemed like a good idea at the time!
Many thanks
Regards Rob
I have a similar problem that I posted some time ago. Someone advised there is a connector on the top right of the engine (near the lhm tank) that is prone to corrosion. I could only find one connector (don't think it was the right one somehow) but the conections were very clean and seemed to make no difference one I played around with it. Problem still persists - though intermitant (seems worse in warm weather). Can anyone offer a deffinative location to the troublesome connector or perhaps an alternative fix?
Hi all,

The connector for the speed sensor is located to the passenger (RHD) side of the LHM tank between the tank and the nearside suspension sphere. Between those two there is a small gap, just enough to get your hand down through. The connector is white in colour. On the 2.5 it is difficult to get to. I found it when I took the head off mine. I pulled it out of position using the slack in the cable and can now get access to it reasonably easily.

Here's a picture of the offending item.

From the connector it is possible to test for the following:

Terminal 1 +12v from fuse 23, live when iginition is on
Terminal 2 0v earth point from earth M2
Terminal 3 "0-10v DC signal alternates" this is what it says in the manual.

For the signal I can't quite grasp what the manual means. Either it is a pulse like a square wave which the ecu counts and determines the speed by itself or it is an analogue 0-10v signal which is relative to a fixed speed range. I can't determine which is correct.

Be aware that the speed sensor sends information to both the engine management ecu and to the suspension ecu. Neither will work correctly of the speed sensor is not working or working intermittently.

Hope this helps

Merry Christmas

noz cool.gif
On the 2.1 its almost impossible to get at without removing the intercooler to turbo pipe and several other things and it is fixed to a bracket which is bolted on to the cylinder head. It is only a two pin plug on the 2.1, Noz. I had to replace the sensor on mine, but I did it when I was in the process of removing or replacing the cylinder head, so had it stripped down anyway. The sensor on mine was actually damaged, due I think to the flywheel bottom cover being missing and the gear ring having picked something up. If you measure the resistance across the leads going to the sensor it should read fairly low, certainly less than 100 ohms, nearer to 50 I think.

The pulse is induced into the coil by a hole drilled in the periphery of the flywheel, so I would think it would produce a sort of spikey sine wave on a scope, but I would think that any sort of pulse at sufficient amplitude would do the job.

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