Hey Guys,

My recently acquired 03 STR has started a random "gearbox fault" message. It will throw the message up, sport mode will dissapear and the trans will not use 6th gear I THINK. The car has 113k miles, and an unknown service history, except for the bunch of stuff I have done.

As soon as you turn off the car and restart it the "gearbox fault" goes away and all is well again, until the next time. It happened once in traffic and I simply shut the car off and restarted the car and drove another 20 miles in bumper to bumper traffic with no issue.

This seems to be caused by a P1797 - According to Jaguar Topix this is a trans code with the following condition: Can network timed out to engine management system, CAN network fault.

This code never throws a CEL Because it never occurs twice during a drive cycle. However my ultragauge saved it as a "pending" code.

I either have a random electrical short or loose wire from the trans to the tcm or between the ecm and tcm, OR the other suggestion is to look at the connector sleeve and see if it is wicking out trans fluid onto the harness.

I'm pretty convinced it's not a mechanical transmission issue because the car runs / drives / shifts fine when the fault isn't present. THE only shifting hiccup I have ever felt was once on the highway in a 95+ degree day cruising at 75mph and put my foot down, and the trans stuttered and didnt downshift. that was the first "gearbox fault". Now mind you I bought this car in poor mechanical shape, and I've been going through it top to bottom. The full story is yet to come.

The other thing is I'm not sure if this is the adaptation or not, but when driving in d on the highway, if you press the gas to accelerate, and it shifts down to 5th, it seems to hold 5th for about 30 sec to a min once your speed has again stabilized and you can feel the shift back up to 6th gear.

Has anyone ever experienced this? I tried driving the car in 5th gear to see if it will have any effect, I haven't had the trans throw a gearbox fault yet in that gear, but it has only been about 35 miles.

Thanks in advance,

George

 

A failing battery might do that.
Or any power issue (bad wires/connections/alternator/...)
Also, just about any minor engine fault since they tend to upset the trans (it's next in line and simply doesn't know what the **** is happening).

And if none of the above, maybe a chafed wire - probably the harness that goes into that sleeve but could be anywhere on it!

 

+1 on battery. I would have the battery load tested first George to rule it out - then go towards the chafed wire possibility in the harness.

 

You know.. I have a load tester at my shop but I didn't suspect it for two reasons.

First it's a non original proper Bosch replacement battery.

Second, it cranks strong on the first try. No hesitation, no dragging.

The car does have an aftermarket stereo on it. With a kenwood kvt-617 flip out head unit with the garmin gnv-53 add on nav unit, Sirius tuner, and cd changer in the trunk. As well as an elemental designs 100x2 amp pushing a set of kicker components in the front. Didnt think much of it but I suppose it's an added load on the electrical system.

I have kept the car in 5th gear today drove it about 80 miles in various situations and so far so good.

I will load test the battery when I have a chance.

Take care,

George

 

Keep us posted, George....

As you know, I'm battling ZF shift issues in Jan's XK8. There's always strength in numbers....

 

Did you ever get to the bottom of this problem ???

I might have the same issue

 

I guess the actual answer is sort of.

I did a pan / filter replacement and a fluid replacement, and knock on wood so far the car has been ok for the next 3k miles. It still has a clunky (and somewhat delayed imho) shift into 6th on the highway. Where it will take 30 sec to a min for the trans to shift back into 6th after a traffic situation dictates a downshift, and the shift to 6th is very pronounced. But there have been no additional faults or codes thrown, and the car seems to drive ok.

Fingers crossed, we motor on.

Take care,

George