From the last time wrote ,I hadn't had much luck fixing the issue.

The a re cap , bought a jaguar xj8 1999 4.0 low mileage, only had restricted performance due to coil pack . But decided to remove a resonator on the exhaust to see if sound changed , after the job was done I started the car and it was in gearbox fault , noticed the s mode button is constantly on .

IV changed the valve body , gearbox service, changed all earth grounding points and gave it a rough look over still in gearbox fault mode. Iv have taken it 2 Jaguar so called specialist and they are confused.

I'm thinking what's the worse that could have happened? Bad earth welding, possibly blew a fuse ? All fuses are working fine.last time I plugged a genetic code reader it came up with cam shaft bank 1 lambda bank1 gearbox fault shift solenoid c I think , but IV changed the valve body code disappeared and came back a while after. Car had a new battery 780cc 95 ah I believe.
Any ideas would be great thanks

 

Why you replaced the valve body based on what ?

 

Hi Jaguar_xj8_v8,

The only way to narrow down the possibilities is to connect a diagnostic scan tool and interrogate all the electronic control modules. Whenever you have the Gearbox Fault warning, at least one diagnostic trouble code is stored, and the code(s) will at least tell you why the ECM or TCM thinks there is a problem. Until you know the code(s), you are just guessing, and that gets very expensive very quickly.

It is certainly possible that during the exhaust work, the wiring between the TCM and the transmission was damaged. Check the electrical connector at the transmission to confirm the pins are clean and free of oil and the connector is securely fastened, and check the wiring harness from the transmission as far as you can access it.

If you get the codes scanned, the Workshop Manual has pinpoint tests for each code to track down the root cause.

Cheers,

Don

 

Don is spot on. You need to scan for codes to focus your attention to
where the fault actually is. I certainly agree with Don as you had no
gearbox fault before the resonator removal and you did afterwards.