Hello and greetings from a new member.

I've been catching the old Gearbox Fault when driving in the rain at highway speeds. The first couple times, I was able to clear the only code, P1000, and get motoring again. However, now the Gearbox Fault and P1000 are displayed within a minute of starting the engine. I can also delay the Gearbox Fault message by keeping the engine above 2,000 RPM.

At the diagnostic connector, pin 6 (CAN + circuit) is only at 2.25 volts.
Battery voltage is at 12.74 volts, isolated, and 13.5 volts at the cables with the alternator charging.

I removed, opened, inspected, and reinstalled the TCM and ECM and found no evidence of water ingress.

Also, isolated the instrument cluster and ABS modules from the CAN circuit to rule-out a CAN module internal voltage short.

I've inspected the fuses, relays in both fuse boxes, and the power leads between the battery and fuse boxes for wire insulation damage.

I've followed the pinpoint tests in the Jag shop manual and am led to believe it's a CAN + short to ground.

Does anyone have experience with these symptoms or an idea as to where I might find the short to ground on the CAN network?

Thanks in advance for your help.

MC

 

Make sure to get the workshop manual or codes PDF or at least use Search and read up that P1000 is not a fault code.

Every time you clear the codes you will get a P1000.

It's actually a pending code, too.

 

Generally.............. The CAN bus voltage is lower than battery volts.

The CAN bus low should be around 2.4V
The CAN bus high should be around 2.6V

There are terminating resistors at each end of the network bus.

Here is a copy of my Student Guide when I went to Jaguar Training more than a decade ago.

It gives an overall view of the system.

bob

 

Great Post Bob.

The resistors are there to prevent signal bounce (echo) just an FYI for those who are curious.