hi all,

I found these codes stored in the car memory:
U1260 SCP (J1850) Single Ended (+) Circuit Failure
U1261 SCP (J1850) Single Ended (-) Circuit Failure

could someone give me more info than the non-saying (for me non-saying) "Single Ended (+/-) Circuit Failure"?

thanks.

 

That seems to indicate a problem with the serial data link (Standard Corporate Protocol network) that connects the Body Processor Module, the Door Control Modules, the Security Locking Module, the various Seat Control Modules and the Major Instrment Pack.

Are any of the door, seat, or locking or alarm functions misbehaving?

 

the following function is not working 100%: drivers seat and steering wheel automatic movement when putting the key in the ignition. You know, moving out to make space to get out of the car and then when you get beck going to the position stored in the memory.

Could that be the source of the message? Any hints how to find the actual problem?

thanks.

 

It is possible those problems are related...but the more common cause of the problem you describe is deterioration of the potentimeters (variable resistors) that sense the position of the streering wheel and the seat.

If it was me, I would just clear the codes and check after a few days or weeks to see if they return. It is possible it is not an actual fault, but just some system glitch or a remnant of a fault code that was set during a previous repair to the vehicle and then never cleared.

 

+1

Would also like to find out what it really means or should I say trying to direct you to.

 

Looking at the electrical diagram, the SCP is designed as a 'multidrop' network, basically a balanced (meaning wires are referenced to one another instead of ground) pair of wires common to all the control modules mentioned above. The message means to me that at one time or another, one or both of the wires of the pair was seen to be either open or at an invalid voltage level by one or more of the modules in the network. The cause could be these wires themselves, the connectors or one of the modules. Since there are a lot of devices all connected together with these same wires, this error alone does not home in on a definite culprit.

 

The U1260 & U1261 DTC's on my '99 XK8 using the SDD/IDS V1.30 shows them to be under the heading of "Instrument Pack". That has it's on section in the '99 XK8 Electrical Manual pdf in figure 08.1 on page 44 of 129.

The DTC's reference a - and a + fault in SCO circuit J1850(+) and J1850(-) which seems as if it's what I'd call a null, or nonexistent circuit, that perhaps exists in an option that's not installed but the module doesn't know how to ignore it.

I'm still trying to track down J1850 to see where that is. It does not show anywhere in the electrical pdf or in the '99 svc. manual 2nd edition so how a person is supposed to figure out what it means escapes me. Which is sometimes easy to do<G>

Even the heading SCO circuit does not appear in either manual !!

 

On one of the net's sites I stumbled on the U1260 codes were identified as a Ford "single wire" code and the same under Jaguar while still saying it was Ford code. Since the older IDS system was a Ford program that makes sense.

On another site their response was that it also possibly indicated a check engine light, service engine light, or similar which also made some sense.

 

J1850 is short for SAE J1850. There are 2 variants, one of them is known as Ford SCP. This is the official formal name of the SCP technology.

On-board_diagnostics SAE

According to the book, these codes mean that, from the instrument cluster's perspective, the SCP data bus is not functional as per the electrical status of pins FC25-13 and FC25-14. Possibly a fault in the IC circuit board. There are many TSBs, I believe...

 

BTW near 7 yr old thread. Can nothing ever be left alone...

 

Since we're still searching for a definitive answer to whythose 2 particular DTC codes show up the thread remains unresolved. The forumexists for just that reason so we can ask and hopefully get answers and it's abenefit for every member if once resolved by someone they post what they found.Until that happens it's still a question in search of an answer.
And it is still unresolved since the closest I was able toget was that it was a Ford code that carried over to Jaguar with the use ofFord's IDS software by Jaguar to create a diagnostic system across what wasthen Ford's PAG group and 'might' indicate something like a check engine light.
I was never able to find any TSB's but I believe with Fordat least it refers to a single wire system that is evidently not giving eithera - or + feedback (hence the 2 consecutive code #'s).
If fmertz is correct about the pin assignments then it wouldbe a problem within the trip computer switch pack where you can set and clearmiles/kilometers, odometers A & B, etc., but mine has never given meproblems so I have to wonder.
In the '99 XK8 electrical manual pin FC25-13 is the singlewire connection to select trip A or B and FC25-14 is a single wire to choosemiles or kilometers an both are momentary ground switches.
I had posted a thread back in probably late 2014 or early2015 asking about this with no answer then either so I was still looking for aresponse as that one series of #'s always returns regardless of anything elsewhen I run a scan and I find that annoying.

 

If you look at the little bit of information on SAE J1850, there are 2 variants. The (slower) "GM" variant that works on 1 wire, and the (faster) "Ford" variant that works on 2 wires. The descriptions on the OBD connector reflect this (check pin 2 and 10):

On-board_diagnostics OBD-II_diagnostic_connector

These 2 versions are not compatible as the electrical signals are completely different. Jaguar picked the SCP/Ford version*

* The only exception, I believe, is the early airbag controller that is wired funny, and uses only 1 wire, as per the electrical manual. My _guess_ is that the early airbag module uses the "GM" protocol, and therefore need its own pin on the diagnostics connector.

 

From the '99 electrical guide, Fig 08.1 (Instrument Packs), it looks like SCP is on pins FC25-19 and FC25-20. My earlier post was from the X103 diagnostics book, which might explain the difference.

It then goes into Fig 19.1 (Networks; Serial Data Links) where it describes the various data buses and how they connect to the diagnostics connector. The reason you can know there is an SCP problem from the perspective of the IC is that the software interrogates it over CAN. As a side note, that 1-wire funky airbag module wiring is described there, too.

 

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I checked the fig.19.1 and it indicates that those 2 pin outs communicate with 6 modules primarily tied to the door and seat modules. I did have a failed passenger seat module but replaced it with a working module and had cleared all the codes subsequent to that install. The other modules are working as far as I can tell.

Is it your thinking that the REAL problem is with the Major Instrument Pack itself and that it is not communicating through those particular pins as the result of a circuit board problem?

 

Unless something is malfunctioning, I would not lose any sleep over those codes. They are for the communication bus, and the bus is designed to be error tolerant.

If a transmission error occurs (which can happen due to electrical noise, sparks during battery re connection, a software glitch, removing and replacing a connector...), it may set the codes, but no harm is done unless you see something actually malfunctioning.

 

+++++++++++++++++++++++++++++++++++++++++++++

I would agree if such a 'glitch' code didn't return despite being cleared. It would seem to me that a code that returns regularly despite being repeatedly cleared you best find out why before either there is an impending failure or it's a problem with a safety related function only apparent in the event of an "event"...you know, like hitting something<G>

 

At this point, I am with Steve, and think you are likely experiencing some form of inconsequential error.

But you can try and work the logic. Why would the IC _need_ anything over SCP? My thinking is that there is some indicator on the IC that needs status from a control module on SCP (which is the whole point of this data bus technology). For example, check the belt buckle. Are they wired in to a control module on SCP as per the wiring diagram? If so, is your seat belt warning light working on the IC? Just a thought.

 

Ok, Please help me figure this one out....When I first bought my XJ8, the air bag light came on and I checked everything I knew to check. Then one day the car would not start. An hour later, it fired right up and worked fine for a week until it happened again. This time, I replaced the clock spring and my troubles all went away. It's been fine for six months....until last night. I shut the car off, left the key in the ignition, left the door wide open. Ten minutes later, I got in and turned the key... NO START! My son put his code reader thing-a-ma-jig on it and read these three codes,U2500, U1261, and P1797. He was able to clear these but still no start. I let the car sit overnight and this morning it started up just fine. I haven't checked the codes today yet. After reading the above, I'm thinking one of you guys just might have an answer to this. So, I'll thank you all now and I really hope for an answer as I'm lost.
Curley

 

#1 suspect is power - usually the battery but also check connections such as grounds.

 

+1 to the above.

How old is your battery? Maybe needs replacing. First, though, when was the last time the battery cables ends were cleaned (both ends). Including the positive high power bus connection on the rear trunk wall. Use grit paper and contact cleaner (not WD40).

For an interesting read, check out this 2010 thread, where God fixed the non-start.... after replacing the battery.
https://www.jaguarforums.com/forum/x...unction-40136/