XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

XJS 4.0 gearbox fault light

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  #21  
Old 03-21-2024, 11:15 AM
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Originally Posted by ptjs1
What is the voltage of the battery immediately prior to startup? And what is the voltage of the battery at fast idle (1200 rpm) immediately after startup? It will be helpful if you can take voltage and the efficiency of the alternator out of the equation.

Paul
thanks Paul,

I'll look at voltage next with a independent voltmeter. I'll put results on this post soon hopefully.

All the best.
 
  #22  
Old 03-25-2024, 12:12 AM
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I've owned the same car for 20+ yrs. and have had identical issue with trans light off and on. There is no code that appears on the window where the clock is. The warning light on the dash at start-up is the only source. It is annoying, yes. If your trans oil is serviced per owners manual, I would ignore it. My car is @ 220K miles and I haven't had any debilitating impact. I would suggest you spray some cleaner under the MAS on the RED part attached and wiring going to it. It's a maintenance item rarely mentioned but I've found it helps. The light comes on as a signal failure to that RED part indicating the trans will loose its shift signal and you may notice a "hard" shift until the light is off as it should be.
Dave
 
  #23  
Old 03-26-2024, 01:10 PM
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Originally Posted by XJS-XKR
I've owned the same car for 20+ yrs. and have had identical issue with trans light off and on. There is no code that appears on the window where the clock is. The warning light on the dash at start-up is the only source. It is annoying, yes. If your trans oil is serviced per owners manual, I would ignore it. My car is @ 220K miles and I haven't had any debilitating impact. I would suggest you spray some cleaner under the MAS on the RED part attached and wiring going to it. It's a maintenance item rarely mentioned but I've found it helps. The light comes on as a signal failure to that RED part indicating the trans will loose its shift signal and you may notice a "hard" shift until the light is off as it should be.
Dave
Tthanks Dave,

My car has only done 65k miles. When you say MAS, do you mean mass airflow sensor?

My car does go into limp mode and resets once i turn off and on.

All the best,

Zarathustra.
 
  #24  
Old 03-26-2024, 01:11 PM
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Originally Posted by XJS-XKR
I've owned the same car for 20+ yrs. and have had identical issue with trans light off and on. There is no code that appears on the window where the clock is. The warning light on the dash at start-up is the only source. It is annoying, yes. If your trans oil is serviced per owners manual, I would ignore it. My car is @ 220K miles and I haven't had any debilitating impact. I would suggest you spray some cleaner under the MAS on the RED part attached and wiring going to it. It's a maintenance item rarely mentioned but I've found it helps. The light comes on as a signal failure to that RED part indicating the trans will loose its shift signal and you may notice a "hard" shift until the light is off as it should be.
Dave
Thanks Dave,

My car has only done 65k miles. When you say MAS, do you mean mass airflow sensor?

My car does go into limp mode and resets once i turn off and on.

All the best,

Zarathustra.
 
  #25  
Old 03-27-2024, 01:01 AM
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  • Yes...I meant Mass Airflow. The RED part I mentioned is the TPI.
  • I have never had mine go into "limp home mode"
  • With your low miles I would suspect Paul's reply correct
 
  #26  
Old 05-10-2024, 01:37 PM
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[QUOTE=Zarathushtra;2734878]Thanks Dave,

My car has only done 65k miles. When you say MAS, do you mean mass airflow sensor?

My car does go into limp mode and resets once i turn off and on.

All the best,

Zarathustra.[/QUOTE


I finally got round to working on xjs today.

Left battery disconnected for a mknth. Started and still same issue.

Cleaned all relay connections, MAS connection, checked all fused and now she seems fine. Only done approximately 5 miles but gearbox light off and gearbox works normally.

Hope it stays so.

Thanks everyone.
 
The following 2 users liked this post by Zarathushtra:
Greg in France (05-11-2024), ptjs1 (05-10-2024)
  #27  
Old 06-12-2024, 01:59 PM
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Hi everyone,

I thought I'd fixed it but unfortunately not.

Can anyone advise if my car has a gearbox ecu and if so where it is?

Thanks.
 
  #28  
Old 06-12-2024, 02:27 PM
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Hello, I have a '93 built in 1992. Right at about 65k miles, the gearbox began acting up. Turns out the rubber parts to the rear transmission mount were worn out. There was way to much play when pusing up on the gearbox from below. Bought a new kit for $200, had it installed and no more problems. Jag does issue a word of warning for the person doing the install. Support the gearbox while the mount is disassembled or the drop in weight could possibly break a switch mounted on the firewall. Anyway, best of luck.
 
  #29  
Old 06-12-2024, 03:04 PM
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Rick,

Did that problem cause the transmission light to come on and the car to go into limp home mode?

Cheers

Paul
 
  #30  
Old 06-12-2024, 03:16 PM
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Originally Posted by ptjs1
Rick,

Did that problem cause the transmission light to come on and the car to go into limp home mode?

Cheers

Paul
yes. Light comes on and limp mode
 
  #31  
Old 06-12-2024, 06:39 PM
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Viraf,

What is your battery voltage before starting and whilst engine is running?

Paul
 
  #32  
Old 06-13-2024, 08:36 AM
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Originally Posted by Zarathushtra
yes. Light comes on and limp mode
yes it did Paul. The rubber gaskets on the rear gearbox mount were so worn out, the gearbox was literally flopping around. The mount should give the gearbox just some slight upward movement but with the rubbers worn out, their was a great deal of movement.
 
  #33  
Old 06-28-2024, 08:56 AM
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Originally Posted by ptjs1
Viraf,

What is your battery voltage before starting and whilst engine is running?

Paul
Hi Paul,

Finally got round to check voltages

before start approx 12.5 v

After starting approx 13.5v, idling at 1200rpm 13.5v.

Do you know if my car would have a gearbox ecu and if so where it is located?

Thanks.
 
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