Upgrading from Mk1 to Mk3 RF receiver...

P38 Monkey · Jan 7, 2022

P38 4.0SE 1997.
Given the battery-flattening tendencies of the Mk1 RF key fob receiver, passing loads of bogus instructions that disturb the slumbering BeCM, I decided to upgrade to a Mk3 version. I have just received a genuine one, but can't get it to work. The old Mk1 is fine and when I swap turn and turn about, the Mk1 works and the Mk3 doesn't. The seller tried it on his P38 with the intention of upgrading, but then found that the one he already had in the P38 was actually a Mk3 (something else was causing the battery drain), hence sold it. The Mk3 worked in his P38 but won't in mine. Nothing about initialising in the workshop manual, which confirms that the RF receiver is not vehicle-specific
Is there some magic initiation procedure?

kermit_rr · Jan 7, 2022

Pretty sure it should just work, maybe you need to clear the RF memory and/or resync the key. I'm not sure as never replaced the receiver but worth a shot

Datatek · Jan 7, 2022

The receiver is plug and play. There should be no need for FOB sync or anything else. Sounds like the receiver is duff.
The receiver is a pretty dumb device, the early ones just receive the FOB or any other 433Mhz signal and convert it to a pulse chain for the BECM. The Mk3 contains a signal processor and so only sends valid signals to the BECM.

P38 Monkey · Jan 7, 2022

kermit_rr said:
Pretty sure it should just work, maybe you need to clear the RF memory and/or resync the key. I'm not sure as never replaced the receiver but worth a shot

Resync the key - I think that means pressing the remote then sticking the key in the ignition within 30 seconds - I have tried that. Also tried various combinations of using the key to central-lock etc etc.
There is no sound or any activity when I press the key fob button, nothing at all - no error messages either. But it is 100% fine with the Mk1 RF receiver.
Looks like a duff unit, but thanks for the info. As ever, on a voyage of discovery with the extensive 1990's computing system that they designed into these fine vehicles...

Datatek · Jan 7, 2022

P38 Monkey said:
Resync the key - I think that means pressing the remote then sticking the key in the ignition within 30 seconds - I have tried that. Also tried various combinations of using the key to central-lock etc etc.
There is no sound or any activity when I press the key fob button, nothing at all - no error messages either. But it is 100% fine with the Mk1 RF receiver.
Looks like a duff unit, but thanks for the info. As ever, on a voyage of discovery with the extensive 1990's computing system that they designed into these fine vehicles...

The receiver either works or it doesn't, either the receiver is duff of just possibly there is a bad connection.
As I said the receiver is plug & play.
Send it back for a refund.

pwood999 · Jan 7, 2022

+1 on send it back for refund. You have no proof it ever worked. Hopefully it was not from Mark Skitt ?

Then buy one of Marty's fob-filters here.

FYI the only way to check the receiver, is with an oscilloscope on the data wire to BECM.

awkwardbob · Jan 7, 2022

Hi, as the previous owner of the receiver I can guarantee that I tested it and it worked in my P38 -but then I found out I already had a ‘green dot’ one and hadn’t realised.

That said obviously something’s obviously not quite right so if you want to send it back I’ll either replace it with the one from my vehicle or refund you, whichever works.

Sorry it appears to have been a bust for you, but we’ll get it sorted.

pwood999 · Jan 7, 2022

Bob, Didn't realise it was one of us !!

awkwardbob · Jan 7, 2022

pwood999 said:
Bob, Didn't realise it was one of us !!

haha, that’s ok, there are a lot of sharks out there

I’m just puzzled why it’s not working…

DanClarke · Jan 7, 2022

If you broke it you bought it?

+1 for Marty's filter units. Works just fine.

P38 Monkey · Jan 8, 2022

awkwardbob said:
Hi, as the previous owner of the receiver I can guarantee that I tested it and it worked in my P38 -but then I found out I already had a ‘green dot’ one and hadn’t realised.

That said obviously something’s obviously not quite right so if you want to send it back I’ll either replace it with the one from my vehicle or refund you, whichever works.

Sorry it appears to have been a bust for you, but we’ll get it sorted.

Many thanks - if you could advise your address for return (eBay nessage best) then I'll get it in the post.

P38 Monkey · Jan 8, 2022

DanClarke said:
If you broke it you bought it?

+1 for Marty's filter units. Works

pwood999 said:
Bob, Didn't realise it was one of us !!

I only buy from the safest of sources!

P38 Monkey · Jan 8, 2022

Well, my P38 does its BeCM thing again....
The BeCM does seem to have a lot of "go / no-go" processes:
"No-Go" means it will not work.
"Go" means it might not work.

tomcat59alan · Jan 8, 2022

P38 Monkey said:
Well, my P38 does its BeCM thing again....
The BeCM does seem to have a lot of "go / no-go" processes:
"No-Go" means it will not work.
"Go" means it might not work.

So it may not be the RF receiver.

Datatek · Jan 8, 2022

P38 Monkey said:
Well, my P38 does its BeCM thing again....
The BeCM does seem to have a lot of "go / no-go" processes:
"No-Go" means it will not work.
"Go" means it might not work.

You sure it's the BECM? It wrongly gets blamed for many things, such as fuse box problems, corroded connectors, wet carpet etc.

P38 Monkey · Jan 8, 2022

Datatek said:
You sure it's the BECM? It wrongly gets blamed for many things, such as fuse box problems, corroded connectors, wet carpet etc.

I was being flippant.
I am sure the Mk3 box i bought from Bob was tested as he says, but it does nothing when I connect it. Tried several times, did the key sync etc, but the old Mk1 box works first time every time and the Mk3 box does nothing at all.
As Bob kindly says, I'll return it to him and then I'll get a Marty filter.

Marshall8hp · Jan 8, 2022

I don’t suppose it is a 315Mhz receiver?

P38 Monkey · Jan 8, 2022

Marshall8hp said:
I don’t suppose it is a 315Mhz receiver?

That implies a different key fob I presume? My fobs say CEL0682 on the label if that helps.
The two RF receivers (my old Mk1 and Bob's Mk3) are exactly as pictured in that 1-2-3 line-up photo.

Datatek · Jan 8, 2022

Marshall8hp said:
I don’t suppose it is a 315Mhz receiver?

That is certainly a possibility even if a pretty unlikely one unless Bob's car is a North American import.

awkwardbob · Jan 8, 2022

Datatek said:
That is certainly a possibility even if a pretty unlikely one unless Bob's car is a North American import.

Hi, no she’s a Nov ‘97 U.K. model although that would imply the Mk 3 receiver was fitted at a later date.
I did have a replacement key made recently from the chaps in North Wales after my battery ate itself but I’m assuming it was the standard U.K. freq.

I’m more than happy to refund, but I’ll check the unit when it comes back to see if it works on my car (I did test it before selling and it worked fine, plug-and-play as you say) -purely for my own sanity.

Just one question, you don’t need to do that ‘clear RF memory’ in nanocom do you ? -I had been doing that a lot prior to testing as the dead (faulty) battery had put my BECM into that ‘ panic’ condition

Upgrading from Mk1 to Mk3 RF receiver...

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