Hi, im new to jaguar.... and cars in general. My XJ6 X300 4.0 1995 has a new issue that I can't seem to find any information on. The car worked fine yesterday, then I parked it in a slope (which I usually don't) overnight; when I went to drive it this morning the Automatic transmission light was on and the rpm's will jump from 0-5000-2000-6000. The car works fine, it shifts fine, and the rpm's are definitely not actually jumping like that. This has to be some kind of an electrical issue, does anyone have any ideas what it could be?

 

Don had some information on how important the correct transmission service level is , with your parking on a slope may have effected that

The on the transmission connector that transmits information between transmission body and the transmission ECU and engine ECU can get contaminated

There is a picture of someone getting this different kind of connector off I'lll have to search for

You can clean this connector without jacking the car and is on the aft left side of the transmission



The connector barrel must come straight aft about 1/8 inch to unlock and only then rotate it 1/2 turn to remove , note the use of tie wraps to grip the barrel

 

The light on the dash had gone away but I still took the connector out and cleaned it, this brought the light back. My guess is that it's damaged by water. The rpm meter on the dash is still acting up, even when the light had gone out. It doesn't show the actual rpm's, it kind of floats around, when I'm doing 90 mph it'll go up to 6000 rpm's when this clearly isn't the case. In Idle it'll show 2000 rpm's. The car still runs fine though, just can't use sport mode anymore.

 

The engine and the transmission have 2 separate speed sensors , the transmission is a output shaft speed located inside the transmission

The instrument cluster Tach come from a sensor on the front of the engine

This sensor will read 1300 ohms as a fundamental meter reading

The CEL code is X

The code does not always show on this item

Clean the connector and the face of the sensor of metallic debris

 

Hello, I have an xj6 x300 sovereign from 95', automatic transmission.

A few days ago the tranny light came on along with some problem with the rpm meter (it shows the rpm's but fluctuates a lot, it'll move between 1000 and 2000 when in idle even though there is no actual change in rpm). I had the car parked on an incline overnight, it was also raining. The car is now in limp mode, it went off for a while but the rpm issue subsided, so I decided to clean out the connector to the tranny on the left side. This brought the light back. I have tried disconnecting the battery, cleaning out the connector, cleaning out the TB as well as trying out the key cycle trick, all to no avail.

Does anyone have any suggestions on what to do, there are no error messages and I'd really like to avoid having to take it to a shop.

Thank you, Sincerely Connor.

 

I forgot to add that there seems to be something leaking from the transmission, there isn't a drop but the whole thing is covered in something wet, probably trans - fluid. I checked the fluid though and it seemed to be fine. Maybe it leaked onto something and broke it...

 

Hi Connor,

I have merged your two threads since they overlap with the same symptoms.

Just to add to Parker's suggestions, the source of the engine speed signal is the Crankshaft Position Sensor (CKPS), which is the one Parker mentioned is mounted on the front of the engine just above the crankshaft pulley. The CKPS is connected directly to the Engine Control Module (ECM), which uses it for its own purposes (ignition timing, fuel injector pulse duration, etc.). The ECM also passes the engine speed signal along to the Instrument Cluster (IC), Transmission Control Module (TCM), and the Air Conditioning/Climate Control Module (ACCM).

So, with that in mind:

If the CKPS signal were faulty or missing, your engine would not start and run.

If the TCM were not receiving the correct engine speed signal, it could not control proper gearshifts.

So my suspicion is that the incorrect readings on your rpm meter/tachometer have to do with the signal from the ECM to the IC. This could be caused by a broken wire, loose or corroded connector, failure of the meter itself, looseness or corrosion of the IC ground, water ingress into the ECM, or perhaps other causes.

What I am not certain of, but suspect, is that if the IC receives an implausible engine speed signal, it can trigger Limp Home Mode (LHM), which can lock the transmission in 3rd gear and limit engine speed to something like 3,000 rpm.

Parking on an incline may or may not have had anything to do with your symptoms. However, one possibility that comes to mind is water ingress into the ECM. Was it raining the night you parked on the slope?

You can see the connections in the rpm meter/tachometer circuit in the manual at the link below:

Jaguar X300 Electrical Guide 1995

Cheers,

Don

 

Hi Don, thank you for the message, it was very helpful. I've taken out the ECM to find that there was major water damage done to the black connection. The water dripped down on my hand as I removed it...


Upon opening the ECM I saw that the previous owner had already been messing around in there with some homemade soldering....

After cleaning out the ECM and the connector I reinstalled it and the problem subsided. I'm determined to fix it without going to a mechanic, as there are very few that do older jags here in Sweden.

Any ideas on how I should proceed? I'd like to avoid buying a new ECM.


The CKPS connector seems to be intact, but it may very well not be. I also looked at the IC and that looked fine.

Any and all ideas are welcome, I'm trying to document the process so that anyone with similar issues can use this for reference.

Edit: I think it's the ECM controlled relay that had lost connection, it had eroded apart and it was also the part that was sodered by the previous owner - not sure if this is the key to my issue...

 

See page 59

http://www.jagrepair.com/images/Training%20Guides/801S%20-%202000.pdf

 

So just bu a new one?

 

The ECU part # is specific to country

https://parts.jaguarlandroverclassic.com/parts/index/part/id/C50.C5017.C5017222.C50172224127/brand/jaguar/

click the + in the box on the page

See also

https://www.te.com/usa-en/product-344111-1.html

There is a British distributor and the connector shell usually includes the sockets and you will have extras from unused positions

The wire side ECU connectors will be damaged

EconoSeal III 070 Series red color not found

You have to 2 oxygen sensor system which only uses the fwd sensors

 

 

Almost a year later and I think I'm near the end of this journey. I do have a few questions though.....

So I managed to get a hold of a new B male connector fully equipped with wires. I soldered all the wires in place and I think I have good connections across the board....more on this later. I finally found a listing on ebay for an ECU with all the same numbers as mine, part #, type code, date code.... I have ordered this ECU and it should arrive soon.

What I want to know is if I should check the solder connections on all the wires before fitting the ECU, keep in mind that it's my first time doing any kind of soldering, let alone electrical work. I checked four of the wires by poking a hole in the wire with a needle and hooking it up to a lcr meter. They all had a good connection and I'd like to avoid checking the rest for two reasons, 1 it's a major hassle to do, 2 I want to avoid damaging the wires any further. Do I have to check the wires? If I have a bad connection and I plug in the ECU is there a risk that it fries the computer? Or can I just plug it in and hope for the best?

My other question is if there is any programming that needs to be done. The computer I ordered should be the exact same as mine as all the numbers match. I talked to one guy who does a lot of work on jags, however, and he said that you still have to reprogram it, is this true?

I appreciate any and all help, thanks!!!

 

From my understanding on the later X8 version after 98 some things needed the correct software version and was labeled

The engine ECU should be the same hardware ( except the V12 ) and the software inside depends on the engine version and country region ( emissions )

Your country region may be the same as England

There is a procedure called a wire wring out that I did with mine with the sensor connectors disconnected and a ground provided on the engine side with the sensor connector

I have a check sheet somewhere on one of my older computers

 

I installed the new ecu and the car finally starts. I do have some new problems though, which I hope someone can shed some light on. When I start the engine something is clearly wrong, the entire car shakes because of the engines uneven movements. The cooling fans are also idle (I'm not sure if they usually are though). When I rev up the engine it becomes more stable (the car shakes less) but as soon as I let go of the gas it goes back to it's original shaking. The engine temp indicator also seems to be completely dead. Maybe there's an issue with one or more of my wires. Any suggestions are appreciated!

Edit: I haven't re-coded the ECU, could that be the cause of any of these symptoms?