AH hah...P0705 Linear switch code. This will put trans in no shift mode. Shift position indicators also will be dark. The switch is either defective or shifter cable out of adjustment. I have first hand knowledge of this issue. If codes cleared will reset...but will return....Not so sure about all those missfire codes....

 

To replace or adjust you remove center console.

 

No point in doing resets, the system has been resetting all by itself.

The battery and power distribution system including the ground side are suspect.

Resting voltage should be 12.5 volts or better measured key off for a semi-healthy system that will not behave strangely.

Resting voltage should be 12.8 volts for a fully charged healthy battery. This will almost never be the case.

Complex vehicles often suffer from ADD. Amperage Deficit Disorder.

More amps are drawn from the battery in starting the vehicle than are put back during the drive.

If you start with a fully charged battery, over a period of time it becomes weaker and weaker.

It's like a bank account that starts with $100 and you take out $5 every morning but only put back $4.75 every night. It will take a while, but the account will eventually be flat.

To check the battery, unlock all the doors, check that the key opens the trunk and undo the ground cable. Measure resting voltage and record. Trickle charge with a smart charger for 48 hours. Remove charger. Measure voltage and record. Wait 1 hour, measure voltage and record. Wait 23 hours, measure voltage and record.

You should see a drop to 12.8v on the last reading.

If it is 12.8v, the battery is at full SOC. (presuming ca/ca chemistry)

If it is above 12.6v, but under 12.8v, try another 24 hour sequence.

If it cannot reach 12.6v resting voltage, the battery is a goner.

Once the battery has been brought to full SOC, reinstall the ground cable and check for further symptoms.

While waiting for the battery charge to complete, time can be spent checking the full power distribution system.

If checking for parasitic drain, the Jaguar spec for a X308 is 30ma or less after 1 hour of inactivity while fully locked.

 

Thanks all, I'll try starting and running the car with a brand new battery I had to buy yesterday for my "other" car which sat un-started all winter (and killed the [older] battery) so I could get to work……

I'll take some voltage measurements also.

Motorcars, I pulled the shifter mechanism apart and noted that the trans went into reverse maybe 3/8" before the notch for reverse. Which part is likely at fault, the linear switch itself, or the mechanical cable portion? Or could it be that the two are out of synch?

Thanks,

Mike

 

Motorcars, I pulled the shifter mechanism apart and noted that the trans went into reverse maybe 3/8" before the notch for reverse. Which part is likely at fault, the linear switch itself, or the mechanical cable portion? Or could it be that the two are out of synch?

Thanks,

Mike[/QUOTE]

It probably is a cable adjustment. 2000 XJR had a bulletin,if p0705 came up to
replace the linear switch. Yours is most likely a cable adjustment.

 

OK, I did some more testing.

Swapped the 2 brown relays shown on the first page with other relays (not each other) with no change.

Tried starting and running Jag off a new battery via jumper cables (Jag battery disconnected, jumper cables to Jag battery cables to new battery). Jag would not start, voltage too low, about mid-9's during start. They are crappy jumper cables and too thin though, so not enough current is able to pass is my guess.

Put Jag cables back on original Jag battery and jumped Jag as you normally would with new battery. Jag starts no problem, but no change in "gearbox fault" error.

Checked voltages.

With original Jag battery alone, 12.31 V at battery terminals.
12.21 V @ forward cable on false bulkhead connector.
21.20 V @ aft cable on false bulkhead connector.

With original Jag battery installed and new battery jumpered to it 12.40 V (Jag ignition OFF).

Set my meter to record MIN and MAX voltage transients and started Jag with original battery installed and jumpered to new battery.

10.59 V MIN voltage value recorded during start.
12.68 V MAX voltage value recorded during start.

Thoughts?

I'm going to finish removing the center console and remove and clean the linear switch next, and set adjustment of the shift cable.

Oh one thing, it always just says "Gearbox Fault" now with both yellow and red lights illuminated. It used to say "Gearbox High Temp" fault, but not anymore.

Mike

 

Well, I have the linear switch out. Looks fine, but says X300 on it, not X308? Is that a problem?

Besides degreasing the contact pads and spring fingers, cleaning them with an eraser, adding a bit of tension to the spring fingers, and putting new dielectric grease on the pads and fingers is there anything else I need to do?

Going to inspect all the solder joints with my magnifying headset, but all looks OK so far.

Oh, is there any way someone could point me to some info showing how to check the switch with a DMM? Something like resistance from each pad to ground or similar would be very much appreciated.

Also I came across a procedure to set the cable adjustment while watching the lights on the PRND bezel, but I can't find it again. Perhaps someone could help me find that procedure, or another one on setting the linear switch in synch with the cable?

Thanks so much,

Mike

 

I reinstalled the linear switch and left it loose. Then I reconnected the battery and started the Jag with the linear switch as far back as it would go. Same "Gearbox Fault" message and lights and same banging into R or D only.

Tried moving the switch the most forward position and same warning. I did notice the banging into gear was less severe in the most forward position, but still only R and low gear available.

I tried cycling the ignition on-off, starting the Jag, and putting it into out of of gear in an attempt to clear the error, with no luck.

Any ideas on what to do/try next?

Thanks,

Mike

 

Alright, I broke down and bought a OBD code scanner/reader. A Cen-Tech, Harbor Freight item 60694 for about $100 after the 20% off coupon. CAN & OBD II Professional Scan Tool

I scanned my Jag to see what I could find. Codes shown were:

P0300
P0302
P0306
P0356
P1230
P1638
P0705

"Pending" codes were:

P1111
P0705 (again)

I cleared the codes using the scanner and fired up the Jag. No codes, no lights. Put her in R and no clunk. D, no clunk. Took her for a drive around the neighborhood and seems to shift fine. Didn't go over about 25 mph, but the trans shifted smoothly and without drama. Drove maybe 2 miles and came home. Manual shifting between 2 and 3 works fine. No lights and no codes still.

After shutting the Jag off I read the codes again. There was 1 stored code, but it was a "yellow" as opposed to "red" as previously.

P0705

Says it is a PRND switch fault. Thinking it means the linear switch? What are the odds the issue is solved? I'll got for a spin on the interstate tomorrow, but didn't want to push my luck with it getting close to dark today.

I'd love to find a diagnostic how-to on the linear switch so I can rule it out or determine I need to pony up for a new one.

Mike

 

This section of the workshop manual may be of some help.

 

Fantastic! Thanks a ton, looks like just the info I need.

Mike