My XJ8 3.2l registered in 2003 has just given Gearbox Fault dashboard warning with P0733 OBDll and P01646 readout.
I reset it and have driven it home maybe 30 miles like this.
It pulls away slowly with no acceleration, but as soon as speed builds up seems OK, as though it is stuck in 3rd or 4th gear.
Arrived home and checked again. This time readout is P0722 still with P01646.
Any/all suggestions would be most gratefully received.
John W

 

According to AutoData P0733 is incorrect 3rd gear ratio
Cause = Wiring, TR sensor/switch, shift solenoids, transmission mechanical fault.

P0722 - Vehicle speed sensor - no signal
Cause = Wiring, VSS, ECM/PCM/TCM

P1646 denotes a possible oxygen sensor problem
Found this if it helps:
P1646 and P1647 on your XJ


P1646 and P1647 are two mighty and very common Oxygen sensor codes. The first (P1646 is for the right bank, here in the USA that's the passenger side) and the other (P1647 is for the left bank or driver's side in the USA). The probable causes are:

1. Oxygen sensor failure: fixes the problem 95% of the time
2. Oxygen sensor circuit failure (either the connector or the cable going to the computer): Fixes the problem 1% of the time
3. Computer failure: fixes the problem 4% of the time

The computer is constantly comparing the upstream Oxygen sensors with the downstream oxygen sensors so it is always recommended to change them in pairs (front and rear for each bank). All you have to do to fix your code is to replace both oxygen sensors respective to your bank. For a guide on which parts to buy look below:


Question: What oxygen sensors do I need?
Answer: Depends on what car... Buy one of each, here is a guide:
1997 - 1998 XJ8 with a 3.2L and a 4.0L engine

• NGK 25620
  NGK 25620
  for the front
• NGK 25573
  NGK 25573
  for the rear

1999 - 2003 XJ8 with a 3.2L and a 4.0L engine

• Denso 234-9016
  Denso 234-9016
  for the front
• Denso 234-4798
  Denso 234-4798
  for the rear

2003 - 2005 XJ with a 4.2L engine

• Denso 234-9030
  Denso 234-9030
  for the front
• Denso 234-4798
  Denso 234-4798
  for the rear

2006 - 2009 XJ with a 4.2L engine

• Denso 234-9125
  Denso 234-9125
  for the front
• Bosch 15373
  Bosch 15373
  for the rear

Hopefully someone will come along and correct me if I'm wrong.

 

Thanks Stevep10.
My apologies for typo in my original post but latest reading was P1722 not P0722.
This seems to relate to Transmission Stall Speed but
really not sure what that means.
Will address RHS O2 sensor after gearbox problem sorted as can't see this has any relevance to gearbox performance.
John W

 

That code still relates to a tranny mechanical failure I'm afraid.
However, before I would condemn the tranny, check the colour, amount and smell of the fluid if you can. If it is black or going black then you have a problem, usually from the clutch breaking down. The drum can also crack and break up. The fluid could also smell burnt.
Question:
When you go from P or N, does it seem like it takes a few seconds to go into gear and then you get a 'thump' as it selects at all? Then it drives through the other gears as normal?
Question:
Has the tranny had a filter and fluid change or check in recent times?

 

Many thanks for your advice.
Haven't checked tranny fluid but will try to do so over next few days. Assume there is drain and filler point located somewhere underneath?

Question:
When you go from P or N, does it seem like it takes a few seconds to go into gear and then you get a 'thump' as it selects at all? Then it drives through the other gears as normal.
Answer:
Starts with everything working normally but put into D and doesn't engage - accelerate and there is a thump followed by apparent default mode straight into top gear with restricted throttle.

Question:
Has the tranny had a filter and fluid change or check in recent times?
Answer:
I bought her with 96k clocked and don't know whether tranny fluid changed before. Lots of paperwork but nothing definitive that I can see.
Have since done about 50k and thought tranny was sealed for life so didn't think to check fluid level or change.

Would appreciate any further thoughts or suggestions.

 

I does sound like A drum failure, but it could still be low fluid. Checking the fluid level is a pain without a lift. The procedure for drain and fill is found in the sticky's, either here or the X100 forum, or just do a search.

 

Concur with RJ237.
Go for the fluid check, refill method before condemning the tranny.
I hate when manufacturers say sealed for life; Vauxhall said the same about their gearboxes on the Insignia, but that was only because no-one had actually tried to do anything with one.
Turns out their gearbox CAN be stripped and re-built after all.
Haven't looked at one myself, and certainly not done a Jag tranny as yet, but it came from a good source, my mate who works very closely with a Vauxhall main dealer.

 

That sounds like the classic A drum failure. It goes like this, wear in the valve control block leads to sticking solenoid, pressure builds up, busts a circlip and A drum is free to move, this movement damages the outer edge of the drum.
Transmission rebuild is the likely fix at this point. There are hundreds of posts on this issue within the forum.
First thing is to check the level, then the state of the fluid, pull the pan and check for filings on the trans pan magnets for signs.
A refill along with filter/gasket and a new valve kit from TransGo 'might' fix it depending on how far along the wear is. If the circlip has gone its a rebuild.