Replacement ECU's

The British company Webcon make an replacement for the Lucas/Bosch ECU which is no longer available as genuine part from Landrover. The ECU replaces part numbers PRC7440 and PRC4764, Lucas numbers 84941 and 84477, mounted on Range Rovers from 1983-89. The cost of the unit (as of 09/1997) was 386£ plus a 100£ surcharge which you get refunded if you return the old unit.

I personally think this is an extremely high price. But if you have no choice you must call them at 01932 788805 in the UK (Outside UK 0044 1932 788805). The photo above shows the internals of the new unit, taking up only 1/5th of the original space.

ECU electronic internals

The following mail was posted on the D90 mailing list some time ago and may be of use for some of us. Thanks to Jeff and all the other list members for their kind help.

Date: Tue, 10 Aug 1999 10:09:42 -0600
From: Jeff Gauvin <>
Subject: Re: [D90] 94 D90 vs RR LWB ECU

Whipping out my "secret decoder ring"...

At 05:21 PM 8/9/1999 -0700, you wrote:
>Well by the wierdest of coincidences I just happened to have a chip from a '93 LWBin the garage. If you peel off the PROM ID sticker then beneath that is :

That's the one!

This tells me it is a 32Kx8 (256 mega-bit) OTP (one time programmable)PROM, which is all you really need to know to make "backup" copies of the ROM for installation into salvaged ECUs from other LR models. I think the manufacturer is SGS-Thomson (, so looking that up I can decode the rest of the
part number: "-20" = 200ns access time; "B" (not 8) = PDIP20 (28-pin plastic DIP [really? I'd have expected a ceramic package]); "3" = temp range (-40 to +125 deg C)

Any 27C256, 200ns, Industrial temp range EPROM (about $4/ea) can be used to make copies (requires special equipment).


Date code? 1995, work week 35. In a '93 vehicle this would mean the ROM has been updated at some point.


Hmmm... tough one! :-) Manufactured and/or assembled in Korea.

>On the underside:

Internal part revision and lot number tracking data.

>> Plus, is it just a standard 28-pin DIP (Dual Inline Package)?
>Huh? :) Yes it has 28 connector pins if that's the question

28-pin DIP = Two rows of 14 pins.

- --
Jeff Gauvin
'94 D90


To this I'd like to add my own experience. When you use any older ECU with flap type air meter (look here for how they look from the outside) you can freely exchange the ECUs as long as they come out of a V8. The Vitesse engine units (a high-power version of the same engine) can also be installed and gives a much peppier driving as the injector timing is different. The stock LR/RR units are pretty much tired above 3500 to 4000 rpm while the Vitesse pulls happily up to 6000 rpm (with the Vitesse cam of course). But be warned that fuel consumption will also increase.