[xj-s] XJS 6.0 V12 Gearbox ECU problem

Hi Everyone,

I’m having a lot of problems trying to work out what gearbox
ecu my car needs. I bought it with no ECU for the box at
all. The car drives but doesn’t change gear, I guess it just
defaults to 3rd when it has no ECU plugged in. Of course
since I dont have the old part I can’t get the part number
off it to find a replacement…

To make things more complicated the engine and gearbox are
not original and have been taken out and XJ12 I think. It
was originally a 5.3 V12 auto and now has the 6.0 V12 with
the 4l80e 4 speed gearbox…

I ordered a gearbox ecu from jag spares international part
DBC12027 it says delco electronics on it - made in USA, but
it was the wrong one. The connector on the ecu is much
larger than the connector on the wiring loom of the car.
Also the connector on the car is a male connection. I have
pictures of the connector if it helps…

Can anyone advise me what would be the best way to work out
what part it is? Or does anyone here have one ?

Any advice is very much appreciated.

Thanks, Marko–
'83 Jaguar XJS Based in St Andrews, Scotland
Scotland, United Kingdom
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In reply to a message from elmarko sent Thu 29 Jul 2010:

Hi , I have done a fair amount of work fault finding with the 4L80E
gearbox on my two cars over the last three years. I have a 4.0l
super charged 95 X300 and a 94 XJS 6.0L both of which have this
gear box. The gear boxes look about the same apart from the outside
gear box looms and the ECU for the gearboxes are NOT the same. The
XJS ECU I had just had out and it has two multiplugs one of which
is larger than the other. This ECU I am sure is a Genral Motors ECU
as I have just got some info from GM Training manual. The XJR I
have has one multiplug and is not the same as the XJS ECU. Please
post some pics of the plugs , ecu you have and I will try to help .–
The original message included these comments:

I’m having a lot of problems trying to work out what gearbox
ecu my car needs. I bought it with no ECU for the box at


97 BMW 540iT 95 XJR6 94 XJS 6.0 coupe 99 Ford
Croydon , SURREY, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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In reply to a message from 540itouring sent Thu 29 Jul 2010:

Hi, thanks for your reply. I have uploaded some pictures of
the connector and the ecu I bought to an album… not
actually sure how to link them to this post though…

The ecu you described sounds like the one I bought it has 2
plugs on it one larger than the other… the part number for
that ecu is DBC12027 and it says dalco electronics made in
USA.

Maybe it’s the other type of ecu I need as the connector I
have on the loom is much smaller…

Ill see if I can link the pictures to here or at least find
them so I can let you see… they are uploaded to an album
here though!–
'87 XJS Racer
Scotland, United Kingdom
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In reply to a message from elmarko sent Thu 29 Jul 2010:

Hi , my service manual says
vin no 188105 - 191494 = part number LHC2400AA
and from vin 191495 = part number DBC12027

My car has what you have but I need more info so best if you give
me a call on my mobile .–
97 BMW 540iT 95 XJR6 94 XJS 6.0 coupe 99 Ford
Croydon , SURREY, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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In reply to a message from 540itouring sent Fri 30 Jul 2010:

Hi , I was thinking about your car and think that as your car came
with a 5.3L engine it would have had a GM TH400 gearbox from new.
This box is NOT ELECTRONIC so no ECU for the transmission or loom
would be in the car. The 4L80E is electronic and was only fitted to
the later 6L engine . This box has a DEFAULT of 2ND GEAR in fault
condition , no power supply or in your case no ECU. The car will
stay in second gear and will be harsh when selecting drive or
reverse gears. Your car will not have the wiring or extra parts
like a TPS for gearbox signal , NO Gearbox relay or gearbox warning
light etc . This would need alot of work and time spent on this to
get the box working . If you search for GM 4L80E on google there
are people that make manual shift kits and other stand alone
electronic shifters for this gearbox and think you would be better
off going down that road.–
97 BMW 540iT 95 XJR6 94 XJS 6.0 coupe 99 Ford
Croydon , SURREY, United Kingdom
–Posted using Jag-lovers JagFORUM [forums.jag-lovers.org]–
–Support Jag-lovers - Donate at http://www.jag-lovers.org/donate04.php

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