My silver RS2 Project

[johne]

Skulduggery afoot........ Dave find relay J342 and unplug it. Car should start. Also check you've got 12 volts on pin 27 of the ECU.

Apologies Kit, on a RS2 you do need the factory alarm unit/vacuum pump connected for the car to start.

hashluck, the same doesn't appear to be true for S2 coupe's but it may depend on the year of the car and if it has the immobiliser key chip system fitted. I don't have all the wiring diagrams for all years to check.

[Tractor Dave]

I did test ohms. They were both the same, about 8 from memory. I ordered two new sensors just in case. Coming tomorrow.

[johne]

They are both just an inductor or coil. They have no active element, just a long coil of wire connected between the two pins (1 & 2. pin 3 is a screen connected to ground). You can check them with a multimeter by measuring the resistance between pins 1 and 2. Don't know the value, probably around 1k ohms but it doesn't matter as long as they both measure roughly the same and not open circuit or short circuit to the case or pin 3 in which case they're toast.

If Autodoc are to be believed, you can have a new one for £25.

[John.]

Johne/Dave What type of sensor is the crank/speed sensor and can it be tested with a multimeter please.

Dave, that car has more secrets than POTUS !

[Tractor Dave]

Ok, thanks. Also found this slightly further up.



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[johne]

That crimp is OE, it's the major grounding point (138) in the ECU wiring loom with a bunch of brown/yellow and black wires going to it. Would be worth checking though that it is still connected to ground.

For future reference:

Injector feeds from ECU:

Cyl 1: br/sw
Cyl 2: br/bl
Cyl 3: bg/gn
Cyl 4: br/ws
Cyl 5: br/ro

The returns are all bl/sw which go to a crimp in the loom and then continue as 1 bl/sw to a relay switched battery feed via fuse S28 and also to the ecu itself on pin 37.

[Tractor Dave]

Anyone de pinned the ecu connections before? Are they junior power time?

[Tractor Dave]

Looking at S2 central schematics, these are the ecu earths.

[Tractor Dave]

As I thought. The loom disappears behind the air box and i cant see what bodgery continues. This wasn't part of the alarm i removed. There must be another box of tricks hidden behind the airbox

[johne]

The speed sensor will give many pulses per revolution of the engine (I can't remember how many teeth there are on the flywheel ring gear) but the position sensor only 1 which alone will make it hard to see. The two sensors are identical so you can swap them over to check them out.

There are a couple of legitimate crimps in the engine wiring loom. Have you got a copy off S2central or do I need to send you one?

[Tractor Dave]

A little update
A set up my scope



I got a good wave from the speed sensor but not so good from the crank position sensor




Not so easy to take pics.

So while waiting for the new sensor I thought I would test a few basics at the ecu. Then I noticed something.




All the brown and yellow wires have been cut and join these black wires. This doesn't look oe to me?


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[K Simmonds]

The vacuum pump for the locking is in the same box as the alarm system but there's no link to the factory immobiliser, that's entirely separate.

I've had a look through the wiring diagrams for the factory alarm (V94) and I can't see any way that the alarm unit can get its oar into the starting of the car. There is the link to the radio but even that can't do any more than set the alarm off ???

Thank you for that info Johne, as it happens that's very useful to me.

[John.]

So if it's not a hall sensor then it's an inductive pulse ?

[johne]

The crank position sensor is just a coil of wire around a soft iron core so all it can do is generate a voltage pulse which you'll need your 'scope to see. It's not like G40 which is a Hall sensor but the same as the ABS wheel sensors for this generation of cars.

[johne]

The vacuum pump is linked to the factory alarm/immobiliser so that could well be the problem.

The vacuum pump for the locking is in the same box as the alarm system but there's no link to the factory immobiliser, that's entirely separate.

I've had a look through the wiring diagrams for the factory alarm (V94) and I can't see any way that the alarm unit can get its oar into the starting of the car. There is the link to the radio but even that can't do any more than set the alarm off ???

That's true for a S2 but having done more digging for Dave the situation is more complicated on a RS2 which I'm investigating.