The only place for a coil spring is up Zebedee's arse
1241 posts

If cleaning up the earth sorted it (at least of awhile) then I would look at either swapping the sensor for the later 2 wire one, and adding in an earth wire to maybe one of the other sensor ground wires in the loom (or even back to the battery or engine ecu directly), or somehow add a ground to the original sensor and again ground that back to somewhere reliable.

The temp gauge is heavily damped so I presume that it will not wander around the centre of the gauge when driving normally and the thermostat opens/closes etc, and I remember when mine got super hot and blew the heater core that it stayed central for a LONG time and then suddenly shot up into the red before it went pop.

There was a known issue with the 1 wire temp gauges and their reliability and I think the remedy was to upgrade to the 2 wire version.

Good to hear that it all works properly with the cable and there wasn't any magic smoke soming out.

Interesting to know about the BT3 Update with DAB - I've not heard of that one before... but at least Grom are being good about it and helping you sort the firmware. I too haven't often had to downgrade firmware on things! But hopefully that will manage to get it all working as expected - I must say that the one I installed a year (or maybe 2) ago obviously didn't have that firmware, as all the track/folder control worked as you would expect it to.

Hopefully the firmware update will be easy enough to do!

Having a look - I believe this is right. The audio grounds (from memory) are tied to the main power ground in the head unit/Grom unit. So the pins you mentioned are to actually power the Grom BT3 unit itself. There should be other wires in the connector aswell to go to the head unit. Hopefully in Pins 13/14 (audio signal L/R +ve) and Pin 19, which is the I-bus control wire..

As long as all those pins are correct along with the power/ground wires - then you should be fine and it'll work as expected.


Yeah, I've been back in NZ now since late October last year.... I was only originally planning on being here for 6 months - but as covid has played out, I've ended up staying here longer and longer.. I do have to come back to the UK at some point (either November this year, or maybe end of January 2022 depending on if work pans out in the USA).

I've been lucky that up until a couple of weeks ago work/life had been pretty busy - but we went back into full lockdown due to covid Delta getting out into the community (we were previously totally covid free in the whole country). So being at home with no work again (and not even any RR bits to work on here!!) I've had to push a few plans again...

I did take a jump to the dark side a couple of months ago and bought a RR out here aswell - though as a first for me I skipped the P38's on offer and took the plunge on a 2006 L322 - the 4.2L Supercharged model... in my typical style, it needed a LOT of work and is currently in getting the transmission rebuilt - and is unfortunately tied up there during lockdown - so can't wait for restrictions to ease so they can finish that and I can get it back and try to do a few road trips!

Re the Thor ECU stuff - it is strange that it was hard coded to the ECU on the P38s - as on the D2 which also used the Motronic ECU, it was the other way around still - the Disco BCU had the code in it, and you then do a security learn on the ECU... I have no idea why they mixed it around on the P38 though....

I will have a look at them in a bit as I'm actually with my laptop and RAVE... But what seems like ages ago now, I did a Grom install for someone with the BT3 unit and also that cable and it worked fine... The blue connector replaces the CD changer input on the head unit... But I will have a look through my notes and pinouts for the Alpine system and double check...

Do you mean this cable?


The GEMS and Bosch systems basically work in opposite to each other.

GEMS listens for a code that is programmed into the BECM (which isn't hard-coded - it's a 16bit/ HEX value you can change it to whatever you want between 0 and 65535). The GEMS ECU then has the 'Security Learn' which basically tells the ECU to listen to the security code being received and then store that as the one that it should use. There were the issues as Davew mentioned where the GEMS ECU would 'forget' the code and lose sync with the BECM, and the fix was to reprogram the BECM code with 65535 and then tell the ECU to learn this.
The GEMS ECU would tell the BECM (via illumination of the Check Engine Light) that it had accepted the code, and a BECM which is set to GEMS would inhibit cranking of the engine unless it had seen the CEL signal back from the engine ECU.

The Bosch units - Motronic and EDC work opposite in the fact that their immobilisation code is stored in the engine ECU itself, and the BECM code is programmed to match this. The Bosch units don't provide feedback on a correct code via the CEL, so this check was programmed out of a BECM, and is the reason why when sync is lost on a diesel or a Thor, that it will still crank, but not fire up. The BECM firmware was changed to always allow cranking in Pos III (except if it was immobilised) as it has no idea if the engine ECU has accepted the code or not. It basically leaves the decision on whether the engine should start or not to the engine ECU.

I'm happy to see that there is a solution now for the Motronic ECUs - though they never seemed to suffer the problem with losing sync like the GEMS units did (well, definitely not to the same extent). I am sure you will get a lot of people snapping them up, because it seems to be the number one worry people have with P38's about it not starting or them being locked out....

One other side note.... I don't know how this affects insurance in the UK as regards to modifications etc - as you are technically removing the immobiliser completely... other than the steering lock, there is now absolutely nothing to stop you from hotwiring a P38 with this fitted is there?

I am somewhat of a purist though, and feel that if you have a well looked after system, then it works fine as it was intended from the factory. The big problem that I usually end up fixing for people with non-starting issues is BECM related - because it's the big bad box of horror stories... despite the fact that most BECM lockout issues are down to components external to that failing and there will have been warning signs long before it actually going into lockout (usually problems with locking/door latches). And why look after the system and have it work properly when you can just bypass all the security....

I do think the possibility of running the Motronic ECU as standalone is great, as it opens up the possibility of using the engine/ECU in standalone environments which previously was only confined to the using the GEMS version... I'm a big fan of the Rover V8 and the thought of being able to use it in other projects - but with the later engine management systems is quite food for thought....

Though lately my interests have been elsewhere...

Looks ace... Can't wait to see it in person!

Have a think what you can do for mine now... Though I want to keep me LPG tank, thanks :)

donmacn wrote:

Dropped another 4.5L of ATF out of my gearbox after letting it sit for another week... think that's about 9L that's come out now. I think I'll need to go any buy another 5L of ATF before I fill it tomorrow.

Meanwhile, in another part of the car.... I think I saw a post recently about the availability of Marty/Sloth's RF key fob filters, but they're showing as 'out of stock' on the website. Can anyone remember that post, or know what the latest is? I have the trim panel off, so I thought I might as well 'future proof' the car and fit one.

We are currently out of stock on them. I am out of the country still with work, and I think Nick is hoping to try and get some filters made in the near future, but we have been waiting on boards and components and he also works full-time, so it's a bit of a juggling act.

We will definitely make more of them, but can't commit to a timeframe at the moment, sorry!

romanrob wrote:

oh joy

Yeah, it's not too bad. I usually use a scalpel blade to scratch away a bit of the black lacquer where the bad track/via is, as there are some tracks that run pretty close to each other and if you're not careful you can then bridge tracks with solder.

It's one of the reasons I didn't get around to fixing any of them before I left for NZ... Though I usually find the ones with the electrical issues like yours easier and quicker to fix than ones with button problems, as they're a while lot more work to strip apart and put back together!

I have Comets on mine aswell.

they were a standard fit D2 wheel, but on the P38 they weren't fitted as a "we have nothing left" but rather an option extra. My 2001 sales brochure shows them as being £800 extra to fit comets on a late model P38 - my 2001 Vogue has them, as someone seems to have ticked a load of extra boxes on the order form.... but my 2000 Vogue (which is still a work in progress) only had the standard Hurricanes on it.

I believe the stored target heights (especially on the front) need to be withing 2 bits of each other - as when you come to a stop, it briefly opens both front valves to equalize the pressure between the front air springs. (I'm guessing to try to make sure the headlights are level and not shining randomly off).

If you have target heights more that a couple of bits out then you might see the 'target heights incorrect' message - or if they are outside the expected range for that particular height.

As to the height it actually reports as sitting at - well, that might be a bit off from the 'target', but again especially on the fronts, they should be withing a couple of points of each other.

Hope this helps.

The phone input on the later Vogue vehicle goes into the DSP amp, not the head unit - so the issue on that one is possibly early signs of a DSP amp failure.

If you're lucky it could be corrosion or something on the phone unit connector which usually hides down in the LHR area near the CD changer unit or maybe behind the trims. The is a mute line and the audio feeds into the DSP amp.

I run the Standard Terrafirmas - and they are definitely a bit stiffer than the stock Boge units that came off, but it does feel pretty sturdy on the road overall.

I am also definitely preferring the Bridgestone Dueller AT tyres I put on last year to replace the Toyo Open Country AT's that were on there. Feels a lot better to drive.

romanrob wrote:

Tnx all...I've been testing various bits for continuity, but no joy so far

Most of the ones I find it's between one of the serial pins and the first through board connection they come to.

Not all of them are like that by any stretch of the imagination - I found one where there were 3 or 4 places where it has failed, but most of the ones I repair have 1, maybe 2 faulty through board connections.

I use a 0.5mm drill in a rotary tool to drill out the crud, and then a thin strand of copper wire soldered either side to replace it and re-join the broken connection.

I've never seen a dead chip on them. Generally completely dead switchpack is a lack of serial Comms to the BECM, but it's down to corrosion damage on some of the PCB tracks/ through board connections as mad-as found with his rather than a dud chip

I can generally repair them, but as Gilbertd says - I'm out of the country at the moment for at least another 6-8 weeks, so not a lot of use to you... I could be interested in the dead one if you have it sorted by then, though from memory I've got about 10 of them already stacked up for repair that I didn't get around to doing before I left the UK...

As Mad-as says... I've pulled a number of the heater boxes apart and freed up the flaps in them. I usually ream the holes out in the heater box itself to give a bit more clearance for the flaps to move in, and also I've found in a number of them that the grease that was used originally had dried up and also instead of keeping things moving nicely actually helps bind things up.

I use silicone grease when putting them back together, rather than the white lithium grease (as it seems to get less greasy and more solid with age).

Also worth checking the alignment of the gears on the main grey spindle, as if they're out a bit then one set of the 3 flaps will get to the end of motion before the others and stall the motor out.

I've also found on a few heater boxes that the drive shaft from one of the sets of flaps has slid out over the years, so one set of the distribution flaps isn't driven properly (if at all).

Incidentally - the last few heater box out/heater core/blend motor swaps I've done for other people have been on later 2000/2001 vehicles and the heater boxes haven't needed any work and seemed a LOT freer than earlier ones. So I wonder if there was a slight modification in the production on them, as the later ones did have a different part number....

I believe you should be able to move ALL of the flaps (including the distribution flaps from one end to the other) with your little finger. The motors have a fair bit of torque in them due to the gearing, but obviously the freer the flaps, the easier life the motors have. I've managed to get some of the earlier heater boxes to be pretty freed up - but a couple of the later 2000/2001 versions that I've pulled out have been really free and easy to move - which makes me think they must have adjusted the tolerances in later production.

I can also vouch for the PAC SWI-RC - used one in my P38 for years until I went over to using the Android head units, which interface directly to the steering wheel controls.

When I was doing some decent mileage in the RR - I would get 75-76L into the tank, and around town I would get between 190-200 miles from a tank, depending on whether it was short hops around the city, or slightly better runs with less traffic, some dual carriageway etc.

On a full motorway run, when I would travel to Windsor and back a few times a week for work in October (ok, so 2019 was the last time I was doing that) I managed 243 miles on a tank - twice... it cut over to petrol at the same roundabout.

My best ever was about 256 miles out of a tank, but that was all motorway driving about 70mph, pretty constantly.

That's pretty much what happened to the ones I tried - but figured as they were already knackered, with the glass in bits, it was worth a go.

Weather out here is nice... though almost too hot at times - especially when I was working outside for 7 hours today... .but I definitely have a tan now!

I genuinely do miss being at home with my own stuff around me and the RR to drive - but the work is keeping me going, as I'd have been even more crazy than I already am if I was sat at home still with no work!