Marquo. Jason had two 964s at one stage and may still do so. He had/has a C4 and a Turbo. The issue is with his Turbo, but the OBD is interchangeable. I was suggesting he switch OBDs on his own cars to isolate the issue.

 

Thanks John for the explanation. Now I understand, it is a good propposition to see if the issue comes from the OBD or from the circuit input information

 

another option could be to go to the official Porsche and ask for a diagnostic check computer to see if there are any message or alert to be considerated.

 

I've just checked my scantool error list and none apply to the OBD.

The official dealer tester may have more functions but its a long shot.

 

That should be a no brainer. I'd start by putting the one that reads P in the car that has the working OBC.

 

The OBC/tacho is not connected to the OBD bus,and it is not possible to use a OBD tool to inspect it.
Cheers,
Tore

 

I think John/Marquo meant OBC not OBD. I'll try to swap the tachos over (when I get a spare second and have the two cars in the same place) between cars but the C4 is a 1990 and I'm not sure an OBC was an option then? Will also try a hard reset (battery disconnect). Let you now...

 

My idea was to connet a OBD to see errors on the OBC, but what Tore is telling us is that OBD is not connected with OBC, so no error would be detected.
Regarding the reset with battery disconnect, it is something that I have checked and any change, the OBC displays "P" after to reconnect the battery.
So, we have only 2 ways to attack the issue:
1) stwich tachos to insulate the issue: detecting if the issue is on the circuit or on the tacho
2) review all sockets looking for any fault in the conexions

 

A customer of mine have now handed in a Tachometer with the OBC reading 0.0. I have a test rig for the tacho, and the unit behaves the same in this as in-car I therefore suspect there's no problem in the car. I've done some work on it to find the fault without results. Adrian Streather's book mentions a possible faulty diode 1N4148 on the LCD board, (he has wrongly called it 1N4118) I have changed it with no results.
I would be very happy to receive some info on how to fix this.
Cheers,
Tore

 

did anyone ever discover what the issue was with this ? I ask because mine is doing the exact same thing currently...flashes the P ...
Thanks in advance....

 

RDH I also am in Central Florida with a 964 and a X50 996TT

 

I still have my "P" flashing on the OBC....

 

Have you tried replacing your obc tacho with a known working one?

 

I'm assuming now that the flashing P simply means its broken and needs replaced

 

Find one on ebay and replace the tach. Or, send it to Hollywood Speedo with $650 and they will fix it. Or, do what I did, get a regular tach off of ebay for $150 and replace it. The only think that you lose is the trip meter.

Mine didn't flash P, it just reads 0.0 and none of the functions would work. Tested it with a working tach w/OBC and everything worked fine. Just not worth the money to me to know the outside temp or distance to empty.