Hello

sorry for yet another limp mode question. I have been reading through loads of threads pulling detail together and think I know the route I am going to take. would welcome ideas pointers or redirection.

First the car XJ308 4 litre Sovereign 180k on the clock Bought nearly a year ago.

BRIEF HISTORY
From a cold start it has been occasionally throwing up a gearbox fault and P0706 message, switch off, and on and cycling the stick through all the gears before making off from cold start cleared it fine. All lights work as they should on the selector.

More recently had an isolated issue with Low coolant message on the dash. checked and found it low, but dont panic as I had swapped out the thermostat a couple of weeks before so suspect that the coolant may not have been topped up. Topped up the coolant and then the engine light came on followed by messages about ABS etc the whole shebang. Parked it in the barn and then got distracted on other stuff for 2 months. + I live 200 miles away from my dad and his barn. I didnt have my ODB reader with me so no choice.

2 Months later, October, the battery was flat, charged it and it wouldn't charge over 11.5v, did a drop test and it was dead so it was replaced with a new unit like for like
Yuasa 5000 Startup Power: 900amps, AH Value: 100ah, Bench Charge: 6 Amps. Fitted and car starts and engine runs beautifully. The dash however is like a Christmas tree. My ODB reader told me....

P0706, P1637, P1638, P1642, P1643, P1646, P1646, P1642
Messages for Trac not available, asc not available, failsafe engine mode, gearbox fault

Parked it up back in the barn for a month until I could research here

THIS WEEKEND
Had a play again yesterday. firstly the new battery was down to 11.5v, no conditioner fitted and it was still connected. my mistake as I knew it wouldn't move for a month.

While I charged the battery for a couple of hours

• I connected the battery terminals for Hard Reset
• Checked out the expansion bottle. No sign of any leak BUT there is some shinyness on the plastic removable cover that smells slightly of antifreeze,
• I checked, cleaned, dried every single connector behind the engine.
• I checked, cleaned, and reinstalled every fuse in the two fuse boxes at the front of the engine bay
• I removed the link cable between the 2 fuse boxes and cleaned it before reinstalling

Reconnected the battery when it was charged up to 12.3v. Ignition on, cleared all codes and started. Yay no messages, no EML, engine running nice. Ran it for a few minutes, then reversed it out of the barn. Dash lit up like a tree - EML, Red and Amber Lights and messages for Trac not available, asc not available, failsafe engine mode, gearbox fault. Also this time there was an error on the heater control screen, it went away after a few seconds. This one is new

Had other stuff to do so went to move it and the stick was locked in Park. Cleared codes and no change, switch off and back on, no change, So ignition on I cleared codes then started and quickly moved the gearstick and got it to drive.

Another new message though about Low Brake Fluid.
The heater control screen shows err each time I start now

Drove it back into the barn but then drive was lost, engine still ran but no power to move the car. Moved it back in park and of course it locked again.

Checked codes and now have the usual P suspects 1638, 1642, 1000, 1637, 1643 & 1646
Messages are Trac not available, asc not available, failsafe engine mode, gearbox fault.
Both Red and Amber lights are on

Checked voltage at battery with engine running 14.13v
Checked voltage at battery disconnected (engine off first of course) 12.13v
Here is a vid if you are interested


NEXT STEPS
Charge the battery up fully, i.e. I believe that it needs to be 12.5v disconnected from the car.
Check the ground points, loads of them, are there any known trouble spots
Double check alternator output at the Battery - is 14.13v good or not? It would be outstanding on my 25year old Range Rover but that doesn't have complex electronics to feed
Then follow CAN Failure – Service Action S484 and check the back of the dash module

Anything else?

When running I want to double check why there is evidence of coolant on the plastic cover of the header tank, I have block testers etc

 

"Reconnected the battery when it was charged up to 12.3v... Checked voltage at battery disconnected (engine off first of course) 12.13v"

Both of these voltages are WAY low, and are likely the cause of your "christmas tree" dash warning symptoms. You are correct that 12.5v is the absolute minimum resting battery voltage on these cars.

It might be worth checking all relays with a relay tester. Relays that are still good (but on their way out) have been known to cause battery drain issues while the car is in storage.

 

Have you checked what the error codes are , they may disappear after you reset them . After that these may be helpful as it relates to the AJ26 engine as I believe yours is the AJ27 of the same V8 series :

http://www.mediafire.com/file/dsq7at...Flowcharts.pdf

http://www.mediafire.com/file/4f96pw...+Diagnosis.pdf

 

Yes mine is the AJ27

Cleared the codes down and done a hard reset. the following are being persistent.

P1637 CAN Link ECM/ABS Control Module Circuit/Network

P1638 CAN Link ECM/INSTM Circuit/Network

P1642 CAN Link Circuit

P1643 CAN Link Engine Control Module/Transmission Control Module Circuit/Network

P1646 Linear O2 Sensor Control Chip (Bank1)

 

Hi Richard,

You can download the Diagnostic Trouble Codes Summaries at this link:

Jaguar DTC Summaries AJ27

As you can see in the column for Possible Causes of most of your recurring codes, a common cause is an open or short circuit in the CAN or ECM failure. In the case of P1646, possible causes include an open or short in the wiring for the A Bank upstream heated oxygen sensor or ECM failure.

Based on these common possible causes, I might consider first checking the ECM electrical connectors for signs of corrosion and cleaning them thoroughly. You could also test the battery voltage at the B+ pins of the ECM harness connector - as Samilcar has already mentioned, sufficient battery voltage is critical, and even if your battery is fine, it's possible that the voltage seen by the ECM might be low due to looseness or corrosion on battery power and/or ground connections throughout the car.

The other common possible cause is an open or short circuit. I haven't studied the schematics to see if a problem in the HO2S circuit could also trigger CAN circuit faults, but you can download the Electrical Guide at the link below to look for common points in the circuits where an open or short could trigger all these codes:

Jaguar X308 Electrical Guide 2000

Note also that some of the persistent codes can cause some of the other symptoms you've experienced. For example, the same faults that trigger P1637 can cause the ABS Not Available/Trac Not Available/gearbox fault/failsafe engine mode. So if you can find the cause(s) of the recurring codes, you'll probably resolve most of the other issues.

Please keep us informed.

Cheers,

Don

 

CAN refers to the Controller Area Network which I believe is the data bus of the multiplex communications between the different ECU's effected . Somewhere the data bus is being corrupted . I would focus on the 1642 code as the others may fall in line after it's resolution . This could be simply cleaning the connectors that I found often to be the case on airliners

 

+1 that 12.3V is far too low.

Sadly it is possible the battery is now dead but it's worth trying a decent reconditioning charger in case it recovers.

With 12.3 you may be chasing fake codes.

However, it's also possible you'e a faulty connection somewhere or mice chewed the wiring.

 

If you are using a defective charger it may induce a bad signal into the car . This is known as dirty electricity as more then one type of electrically can exist in a wire at the same time . What you desire is a pure DC battery sourced signal . I have seen it myself with a bad charger . You could see the car's own voltage meter flicker as well as seeing the data bus effected by this corrupted electricity .

Suggest fully charging up the battery to the 12.77 volts from a different source , reset the codes as you hook up your car with battery only , no charger hooked up at the same time .

If that doesn't get you anything I would suggest a " Hard Reset "

1. With the key in the on position , not running

2. Remove both battery cables

3. Touch both cables in the air together ( the longer the better as in overnight with a clamp or jumper cables )

4. Don't let the cables touch the battery post as you will have to start the sequence over . Put a towel over the post .

5. Turn key to off and remove key

6. Rehook the battery cables to battery post

This will in no way harm anything but it resets or reboots the ECU's back to zero state without effecting the ECU's operating software or firmware .

The engine ECU will have to relearn the Long Term Fuel Trim so it will be off for awhile until it relearns it .

 

fixed

charged the battery up good n proper, did a hard reset

after settling but disconnected 12.7v
battery connected and running at idle 14.2v
while running and disconnect earth lead, measure voltage between +ive and earth lead 14.4v

Alternator is working fine.

Cleared all the codes down and the car is behaving.

just one code remains aside from P1000
P1646 Linear O2 Sensor Control Chip (Bank1)

Is that the lambda on the uk drivers side of the engine. i.e. on the left side of the engine when facing the front of the car?

Lack of Mot, VED and insurance prevented a victory test drive

the car did stall on selecting gear. looking into that now but it hasnt been used since July, probably needs a good run

 

The workshop manual lists all the possible causes - it doesn't have to be the sensor but commonly is.

 

Bank 1 always contains cylinder # 1 , not to be confused with firing order . Good measurements on the battery / charging system . P1646 may " unlatch " or reset after a few engine run cycles which includes time and RPM targets . So I would leave it alone for now , if it was me . The on the transmission connector can be cleaned without jacking the car as a dirty connector will stall the engine Ensure that you have the proper transmission fluid service level as this will stall the engine as well .

 

Hi Richard,

That looks like a generic code definition from your scanning tool. It's prudent to always consult the Jaguar X308 DTC Summaries guide available at the link I posted earlier, because the Jaguar definitions and possible causes often differ from the generic OBDII ones. Here's what the DTC Summaries say about P1646:




If your OBDII scanner can read live data, you can observe the behavior of the Bank A / 1 upstream O2S to see if it is reasonably similar to that of the Bank B / 2 upstream O2S. If not, suspect a problem with the sensor wiring or the sensor itself.

Here's how to identify Bank A / 1:



Cheers,

Don

 

Car was MoT'd on Friday yay

Thanks to all on here for advise. my Dad is very happy.

In summary the initial root cause of issues was dead battery, jaaaag cannot operate on a battery that has less than 12.5v at rest. it showers the ecu and eml with ghost errors.

I recognised that the battery was dead and bought another from Halfords but errors persisted. On testing the battery had just over 12.3v I now know that is not enough.

I trickle charged it to 12.7v and all errors were cleared and stayed away. the flickering gearselector light is to do with my odb2 reader. disconnect and the light is steady.

After a test drive the eml popped up again. p1646 drivers side upper lambda and p1000 .

Naturally I was 200 miles away so dad now confident that it wasnt going to launch into limp mode and die on him motored it down to the local test station.

A brief check using a realtime odb meter found the upper drivers side lambda off the scale. new sensor fitted and pass was issued.

The car goes like stink again, gearbox chitters slightly on gear change, zorst emits pleasing woofle. I think dad went through half a tank of fuel yesterday to celebrate.

Verdict, dad nearly lost all hope at the original list of errors, he was thinking about selling spares or repairs or chopping it in to a breaker. If it hadnt gone into limp mode I suspect he might have achieved that objective. It was fixed for the exorbitant cost of £130 for the battery and £90 for the oxygen sensor. oh and a little thinking outside the box, I try to keep away from CAN electronics normally but am getting used to some of the anomalies.

 

Could have been so much worse! Good to hear & let's hope it stays affordable - er, apart from the fuel!