[Dodger1960]

I have occasionally had the "cascade" of transmission fault/special programs/HDC/lowered suspension along with the normal steering angle sensor light and the lack of ABS. However, while this was normally reset with a restart and left lock / right lock, the issue now seems to have become permanent and putting my IID on it I get the fault below. Clutch position in rear diff not learned...

Any clue as to what the underlying cause is? My previous understanding (ignoring the diff clutch not being learned) was that this stemmed from the steering angle sensor. When that gave a bad message then it caused the other failures including HDC inactive, ABS inactive and lowered suspension.

The steering angle sensor light now flashes all the time and no amount of left lock/right lock makes a difference...

Any and all assistance gratefully received

 

[NoExpert]

How old is the battery? Have you had it tested? Has the alternator been tested?

 

[Dodger1960]

The battery is only a month old and my CTEK says it is good condition. I have not specifically tested the alternator, when the engine is running the IID says the voltage is 14.3v

 

[NoExpert]

14.3v is kind of weak for how electrical heavy these cars are. I get 14.6-14.8v out of my alternator.

 

[Dodger1960]

Thanks NoExpert. I will check the voltage output and go from there. I may be suffering brain fade...

 

[Dodger1960]

Just had the opportunity to recheck. Resting voltage of battery is 12.6v. When running the voltage is 14.6v

 

[NoExpert]

Okay, so we can eliminate that from the list.

Next up have you tried calibrating the SAS using the GAP IID? Personally I’d skip this and jump straight to “install new module” which most often takes care of it. By “install new module” I mean just tell it there’s a new module in diagnostics and let it install new software and calibrate it. Just did this Friday on a Disco 4 that cooked its battery and alternator. Lots of faults including SAS. Cleared everything that would clear, told it there was a new module, installed software, calibrated, failed, tried again, installed software, calibrated twice and success. One difference is we use the factory JLR-SDD software, so may or may not work with GAP IID.

 

[Dodger1960]

Thanks. I have been reading the IID manual and did notice that it included routines for SAS replacement - it did not occur to me though to simply tell the tool I'd replaced it, even though I hadn't. I will definitely give that a go. Apparently the code I got left over (P080A) means I have a diff lock motor and that it is potentially sticking so looking into how I might "unstick" it.

 

[NoExpert]

Only ran across that once and the owner opted to just unplug the rear diff due to cost to repair/replace. Sadly rear E diff is not something that’s activated often so they tend to stick or seize.

 

[hamiamham]

Not sure if this helps but I was having the same issue as well. It ended up being something called the rear differential locking motor. My mechanic - who only works on Range Rovers - said he had never seen one fail below. But mine did...

 

[Dodger1960]

Thanks for your reply Hamiamham. After much research I am also convinced this is either the motor or gearing for the actuator on my rear diff. I intend to remove at the weekend and go from there. Bushes can apparently be found and even a good clean is often good enough for more life from this component. Thanks again!

 

[lcdrjoe]

I had this same symptom a couple years ago on our 08 RRSC. It turned out to be a few bare wires on the bundle that goes on the passenger side toward the rear. I had to remove the front passenger seat and the carpet beneath the seat as well as the door sill. Down there was a wire bundle with at least 50 wires in it running in a channel from the front to just behind the seat foundation and making a turn toward the center of the vehicle. What appeared to have happened was that a few of the wires had worn through the insulation and were occasionally making contact with the metal channel. I could bring on the faults instantly by grounding those wires to the channel. I took some liquid electric tape and spread it on the exposed wires and put a piece of rubber in the channel too. The exposed wires were in a straight portion of the channel just below where the front of the passenger's seat would have been. I haven't had the issue again since.

 

[bkwanab]

Okay, so we can eliminate that from the list.

Next up have you tried calibrating the SAS using the GAP IID? Personally I’d skip this and jump straight to “install new module” which most often takes care of it. By “install new module” I mean just tell it there’s a new module in diagnostics and let it install new software and calibrate it. Just did this Friday on a Disco 4 that cooked its battery and alternator. Lots of faults including SAS. Cleared everything that would clear, told it there was a new module, installed software, calibrated, failed, tried again, installed software, calibrated twice and success. One difference is we use the factory JLR-SDD software, so may or may not work with GAP IID.

Not so fast. You didn't ask if the 'new' battery is the correct size. Land Rover specified two different size batteries for the L322, depending on configurations. Many people will install the smaller 'option' as it is considerably less expensive. This can be a mistake. Our L322 vehicles draw a lot of current at startup and immediately afterwards. The CMOS technology employed in the multitude of computer chips in our modern vehicles demand clean, stable voltages to function correctly. Slightly low or intermittent voltage supply can result in lost bits that result in errors that can cascade around the CAN bus leaving spurious faults in unrelated places.

When we bought our used but in nice condition 2006 RR SC the dealer informed us he's installed a new battery that week. With the benefit of hindsight that should have been a warning. Over the following few days the car reported various errors, mostly with the transmission, steering angle sensors and the sir suspension. I soon figured out the battery the dealer had installed was technically correct but actually wrong. I replaced it with the larger, higher capacity battery and most of the errors went away. The air suspension was solved by replacing the compressor with a Chinese copy that looks identical to the RR original and works perfectly.

Replacing the transmission filter and oil reduced the intermittent errors and after some weeks of driving they went away too. I suspect a sticking solenoid was causing the errors.

I can report that now nearly a year later the problems have not returned. It is currently very cold here yet I can start the RR, and immediately turn on the heated steering wheel, seat bum warmer, heated windshield, screen blower to clear the ice and the headlights too. I know the screen/headlight washers and heated mirrors are on, the headlights are on as well as the Hermon Cardon amplifier cranking out the beats. The air compressor often runs immediately after startup if the car has not been used for a couple of days. Thats a lot of load on any battery. But with the larger capacity battery all is well.

 

[Dodger1960]

Hi there bkwanab. The new battery (only a month or so old) is indeed the correct size, capacity and CCA. It is in good condition too, reporting the full voltage that it should be as a fully charged lead acid battery (12.6v at rest). When running the voltage is 14.6v which about dead on and consistent so I think the alternator is also fine (for now).

As mentioned earlier in the post I have tracked this down to a sticky/dead motor on the rear diff clutch. I absolutely agree with you about the battery being the primary cause of such cascades - I've had a few myself and just as often as not caused by the terminal connections rather than the battery itself. In this case, the start up procedure tries to activate the clutch in the diff but because the motor is duff, it returns an error. That leads to a transmission error because the clutch in there is part of the transmission. That then leads to the special programs failure because without the ability to lock the diff, most of them would not function correctly. That in turn leads to HDC inactive (with the turn off of ABS as well) and then finally, as HDC is no longer active the car thinks it should lower the suspension to reduce roll as the suspension can no longer rely on HDC to try to keep the car as level as possible in the curves which of course also relies on the steering angle sensor. That is my understanding at the moment. And all down to a duff motor on the rear diff that has never been locked as far as I know. My fault perhaps for not driving off road much or at all. Its lack of actual use probably led to its demise.

I will be removing the motor and actuator at the weekend if it warms up here a little and then check the electrical connections, bushes etc and lube up the actuator itself. I hope that solves it at least for a while because while I know I can get a replacement for around £160, I don't have the software to recalibrate and don't want to think about whether this issue has burnt out the clutch in the diff. We will see.

 

[bkwanab]

Hi there bkwanab. The new battery (only a month or so old) is indeed the correct size, capacity and CCA. It is in good condition too, reporting the full voltage that it should be as a fully charged lead acid battery (12.6v at rest). When running the voltage is 14.6v which about dead on and consistent so I think the alternator is also fine (for now).

As mentioned earlier in the post I have tracked this down to a sticky/dead motor on the rear diff clutch. I absolutely agree with you about the battery being the primary cause of such cascades - I've had a few myself and just as often as not caused by the terminal connections rather than the battery itself. In this case, the start up procedure tries to activate the clutch in the diff but because the motor is duff, it returns an error. That leads to a transmission error because the clutch in there is part of the transmission. That then leads to the special programs failure because without the ability to lock the diff, most of them would not function correctly. That in turn leads to HDC inactive (with the turn off of ABS as well) and then finally, as HDC is no longer active the car thinks it should lower the suspension to reduce roll as the suspension can no longer rely on HDC to try to keep the car as level as possible in the curves which of course also relies on the steering angle sensor. That is my understanding at the moment. And all down to a duff motor on the rear diff that has never been locked as far as I know. My fault perhaps for not driving off road much or at all. Its lack of actual use probably led to its demise.

I will be removing the motor and actuator at the weekend if it warms up here a little and then check the electrical connections, bushes etc and lube up the actuator itself. I hope that solves it at least for a while because while I know I can get a replacement for around £160, I don't have the software to recalibrate and don't want to think about whether this issue has burnt out the clutch in the diff. We will see.

Well done. It looks like you know what you're doing and have a handle on the problem. You've inspired me to find out if our '06 RR SC has the rear locker installed. I've read there was a software up date so I may be able to check the service history. The car was serviced regularly before I bought it as it was a leased car driven by a woman with children based upon the detritus I removed from under the seats, carpets and console. Good luck with the repair.

 

[Dodger1960]

Oh, I sympathise. Nothing worse than sweetie drool and gummy bears under the seats - which is what I found amongst other less sweet smelling offerings... I know of the software upgrade as well, but again, you have to have full JLR software to do it - not aware of it being offered even as a priced item under IID. I will let you know how I get on. Not sure where you are on the north American continent, but happy Friday and have a great weekend.