Hi all,
Having now put 600 miles on my 2005 XK8 I have noticed a rather harsh upshift from 1-2.

I have trawled the various forums and this appears to be quite common and can often sorted by a hard reset followed by putting the transmission thru a new "Adaptive Learning" cycle". I am unclear has to how the adaptive learning happens.

I have read various post hard reset procedures to retrain the transmission. One thread (https://www.jaguarforums.com/forum/x...-adapt-223607/) albeit on the X150 but for the ZF 6HP26 suggests this procedure based on the the Jaguar Transmission Technical Manual published in 2005 for the ZF 6HP26:

Service Procedures

Adaptive Drive Cycle
After TCM reprogramming, it is advisable to perform
an adaptive drive cycle.

General Conditions:
• Make sure that the A/C is switched off and that Sport
mode is not selected.
• The transmission oil temperature must be warmer
than 60°C (140°F). The vehicle should be warmed
up by driving with various speeds and loads in
normal mode.
• The cycle must be performed at least five times.

Normally Aspirated Vehicles
1. Light throttle upshifts up to 80 km/h (50 mph) with
all shifts occurring between 1300 and 1800 rpm
2. Coast down with light brake to standstill
3. Wait at standstill in drive with the footbrake applied
for at least 15 seconds

Other suggest just drive the car in your preferred style and the TCM will learn afresh.

Which procedure is correct?

Phil

 

If by “hard reset” you mean disconnecting the battery for a time, then the transmission will not lose its adaptation and there is nothing that you need to do specifically.

The adaptive cycle requires the dealer software to trigger it and you also need the same software to clear the old adaptations.

 

You're right to look into this. I would be concerned to about harsh shifts, and you shouldn't let this carry on for too long without fixing it. A broken gearbox can be a car killer due to the low value of our cars - replacing it would be purely for sentimental reasons rather than re-sale.

When was the last time the ATF fluid and filter was changed? If not done recently, it's over-due. DIY-able with good instructions on this Forum and may fix your problem too.

 

As posted already, a hard reset does not reset the trans.

A "small" (*) engine issue can upset the trans, causing hard shifts, so make sure you get all OBD monitors set soon (if not yet) and that the only code you have is a (pending) P1111.

Then check the fuel trims are good.

(*) small to many owners, not necessarily to the car

 

Hi all,
Thanks for the advice to date.
Clearly the Hard Reset does not reset the Transmission.
Yet there are quite a few posts on the Internet suggest that the Hard Reset has transformed the way their cars perform.

My car had a transmission oil change 7k miles/5 years ago.

I have a OBD reader and I'll see if I can get some readouts on the Fuel Trims. What are acceptable ranges for the fuel trims under different loads?

Phil

 

Start with the usual (and easier) ones: hot engine, parked. At idle then rev to about 2500 and see where they settle.

LTFTs are what you want so long as the STFTs are not doing much.

 

Fuel trims are subtraction or addition to the base fuel table. Should be close to zero. Codes are triggered at + or - 25%, but you can "feel" them as they get higher. Ideally, should be below, say, 5%.

 

Hi all
I have collected some fuel trim data today at both idle and at 1500rpm. Parked up at operating temperature after a drive.

Idle
Bank 1 STFT 0.78%/LTFT 7.8%
Bank 2 STFT 6.25%/LTFT 0%

At 1500rpm
Bank 1 STFT 10.9%/LTFT 1.56%
Bank 2 STFT 6.25%/LTFT -0.78%

These look a little odd to me (not that I've seen any before). Can someone more experienced help me with understanding these readings.

Thanks
Phil