p1638 fault

[bharrt]

Hi All,

any ideas what can cause P1638 error code?
started the car from cold and drove 100 metre and dasboard light up as xmas tree, but none of the instruments were working, stopped the car and started again and everything started to work again, but the engine fault light remained and had the code checked with turned out to be P1638 CAN LINK ECM/INSTM CIRCUIT/NETWORK any ideas?

[BigNige]

http://www.2carpros.com/makes/jaguar/xjr.htm

About halfway down.

[Tame Technician]

"P1638 CAN LINK ECM/INSTM CIRCUIT/NETWORK"

Exactly what is says on the tin really. Open circuit or poor connection on the CAN network between the ECM (engine Control Module) and the IPK (Instrument Pack)

And or ,either a faulty instrument pack or fault engine control module causing the pair of them not to communicate.

[bharrt]

thanks, any idea were these modules are located and there connections?

[Tame Technician]

What jag is it??

[bharrt]

car is XJ6 aluminum body 02 plate
when the fault happened all the dashlights came on and the gauges failed to show any reading,
if anyone knows were these connection are and how i can get to these would be great.

[Tame Technician]

Didn't think X350 started until 2003. But if its an aluminium XJ6. Then its a X350. Maybe your is preproduction.

X350 has 4 Different Networks, and depending on spec, over 20 different ECUs on them + probably a few miles of wire. See diagrams bellow (when I get round to posting them that is)

IMPORTANT, The CAN wires are always twisted pairs, one wire Yellow + one Green. When you look at any vehicle wiring harness, even when there is a mass of wires only network wires are twisted in this way so can easily be identified. And only CAN network wires are twisted yellow and green.

Well the wiring connections for the Instrument pack are on the back of the instrument pack, you will need to remove it to get to the multi plugs round the back. 2 small-ish connectors.

The ones for the engine control model, I cant remember if there under the bonnet or behind the glove box, but the Engine ECU is attached to the bulkhead on the passenger side. One massive connector.

From the wiring diagram:-
Its pins 8(Yellow wire) and 9(Green wire), that are the CAN network connection on the instrument pack. There are two connectors and I cant tell which one it is, but only one will have yellow and green wires on 8 and 9.

Pins 123(Green) and 124(Yellow) on the Engine control module are the CAN connections there.

CAN network faults are notoriously difficult to diagnose. Because it could be either of the two modules reporting no comms, a poor connection between said modules and the wiring harness or the harness its self at fault. And any wiring fault can be anywhere on the harness between the two modules, and thats lots of wiring, most of which you cant see or get even get to easily.

The fact that the gauges dropped to nothing is making me think it could be the instrument pack faulty, But I was with Jag for 7 years, 4 years of which X350 was in production and I never fitted one at all.

You've got your work cut out there. Given the potential aggravation I'd advise clear the code down, to put the light out, and drive it to see if it happens again. Could have just been a software crash in the instrument pack, might not happen for another year or so, switch ignition off and on, away you go.

Good Luck TT

Edited by Tame Technician on Thursday 22 October 20:22

Edited by Tame Technician on Thursday 22 October 21:52

[Tame Technician]

[bharrt]

Thanks for the information , i will clear the fault down and see what happens,
can you send me the wiring diagram when you have sec, also is there a quick way and easyway to remove the instrument pack? cheers Taj