XJS ( X27 ) 1975 - 1996 3.6 4.0 5.3 6.0

Trip computer reads 8.8:8.8

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Old 04-13-2018, 10:48 PM
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Default Trip computer reads 8.8:8.8

has happened a few times now. Start the car and trip computer reads 8.8:8.8!

a couple of times switching off and restarting has fixed it.

Anyone know what it means? Is it a fault code? Tried googling it and while I found a thread or two that referenced it I couldn't see what it meant or how to fix it.

i wondered if it's low battery because the clock has reset a few times too.

Greg
 
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Old 04-13-2018, 11:21 PM
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Sometimes just removing and re-seating the connectors will solve mystery faults with the t/c. Weak solder joints on the circuit boards are a likely root-cause....common with 20-30-40 year old electrics.

Lack of voltage supply (using occurs while cranking) can cause weird faults as well....so you may wanna check for excessive voltage drop.

Cheers
DD
 
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Old 04-18-2018, 10:54 PM
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An update for those who might visit here in the future.

pulled fuse #7 under the dash thinking this would cut power. It did but made no change.

pulled the TC from the dash and disconnected wiring, left it 2 minutes, reconnected and all working fine.

 
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Old 04-19-2018, 11:01 AM
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Could you also correct that by disconnecting the battery?
 
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Old 04-19-2018, 11:05 AM
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Originally Posted by RonaldP
Could you also correct that by disconnecting the battery?
I doubt it. I suspect the trip is working because the connecting plug was effectively "cleaned" by separating and reconnecting it.
 
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Old 04-20-2018, 06:05 AM
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Originally Posted by RonaldP
Could you also correct that by disconnecting the battery?
while researching this I read this might work but was advised against it as it may reset other things like alarms etc. that's why I tried the fuse thing.

as Greg from France said pulling the connectors may have also cleaned them to some degree too.

 
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Old 04-27-2018, 04:58 PM
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I would agree with Doug here and suspect a dry solder joint in the TC, 8.8.8.8 is unlikely to be the connector as this is more like the CPU hosing up. Removing the TC was enough to have the joint reconnect, if this re-occurs then I would open the TC and re-solder everything on the PCB.

A good way to fault find dry joints is tap the PCB with the handle of a small screwdriver, works a lot of the time. I tend to use hot and cold hairdryer/heatgun and cold in a can (spray freeze).
 
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Old 04-28-2018, 01:52 AM
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Warrjon
My trip computer once read 8888 etc when the battery was low and the car was cranking, which is why I suspected a connection problem.
 
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Old 04-28-2018, 03:08 AM
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Thanks guys. I've been having low voltage issues lately.

TC has been working since I 'fixed' it but I'll keep this in mind for next time.

I have discovered on my XF that 90% of the issues I've had on that are related to low voltage too - not that I have had many. Seem as though the first thing to check on these cars is battery before fiddling with anything too much.
 
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Old 04-28-2018, 04:27 AM
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Originally Posted by Greg McDonald
..... Seem as though the first thing to check on these cars is battery before fiddling with anything too much.
That advice should be printed as a warning in large letters on the front of the Owner's Handbooks. It applies to ALL Jaguars.

Graham
 
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Old 04-29-2018, 04:56 AM
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Originally Posted by Greg in France
Warrjon
My trip computer once read 8888 etc when the battery was low and the car was cranking, which is why I suspected a connection problem.
CPU's usually run on 5v with a precision regulator, maybe the TC does not have a reg, I have not had open mine. So it is possible.
 
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Old 04-29-2018, 10:09 AM
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Greg Mc:


Exactly what mie dd at one time ands then not even the 8's!!!


DD mentioned a common cure for computers. It works here as well. A hot reboot.


I removed mine from the fascia. Disconnected each of the connectors and cycled the ignition switch a few time. Eureka, 0's appeared. Why 0" Oh, no data to process!!! Set the clock and back to function. Odd as it expects 6 cylinder pulses but gets 8!!!!! Not to mention odd speedo datum. Oh, well, the clock works!!


Carl
 
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