k bus fault or bcu?

the problem i have shows as k bus fault on all comms.the symptoms are that on entry to the vehicle none of the systems are energised,nothing on the instrument binnicle, the sat nav monitor and the transponder coil isnt energised.fortunatly it goes into backup mode in which the car can be started on the second turn of the key after a 2.4 sec delay and everything comes back on line. at first i thought it was prob the steering colomn ecu but if that was the case surely the sat nav screen would energise as this is not on k bus? is it more likely to be the bcu as that energises the car once the doors are unlocked. any thoughts would be appriciated.

paulvasey said:

the problem i have shows as k bus fault on all comms.the symptoms are that on entry to the vehicle none of the systems are energised,nothing on the instrument binnicle, the sat nav monitor and the transponder coil isnt energised.fortunatly it goes into backup mode in which the car can be started on the second turn of the key after a 2.4 sec delay and everything comes back on line. at first i thought it was prob the steering colomn ecu but if that was the case surely the sat nav screen would energise as this is not on k bus? is it more likely to be the bcu as that energises the car once the doors are unlocked. any thoughts would be appriciated.

Click to expand...

More likely to be the stuff in the left rear quarter of the boot is damp.

No, not this time datatek. That is not the case this time , all that area is covered , insulated and vented, it's bone dry. I'm sure it's the bcu or one an ecu on k bus, just don't know which one?

The K Bus runs all the Body systems i.e. HEVAC, Seats, Immobilisation ECU, Steering Coloumn, Rain Sensors, SRS etc etc....

When you put the key in the ingnition, do you get the solenoid click to unlock the steering and be able to turn the key??

I would assume so as you can turn the key as you say you can!

My thoughts would be with a dicky Ignition switch or BCU, as if it was the Immobiliser at fault and all you had to do was turn the key again within 2.4 seconds to 'overcome' the system, that would seem like a pretty ****e bit of security if you ask me!

Check the ignition switch connections are sound and the BCU is dry and sound (even the L322 can get a damp BCU).

As you say the SatNav is on the I bus...so it seems like the BCU isn't getting the wake up signal from the ignition switch!

Mmm do you concur that it is the inhibition switch that wakes up the bcu? I was kinda guessing that the the bcu is activated when the car is unlocked by the the key fob ? Which in turn energises the transponder coil , screen and instrument binnacle ?

I meant ignition switch not inhibitor switch !

Yep the Unlock Signal from the key, tells the BCU to unlock the doors and warm up the Sat Nav computer to display the Land Rover logo...

It then sits there waiting for the switch on all systems signal from the ignition switch, once it has this, it wakes up all the other systems, Instrument Pack, HEVAC, Engine ECU, Gearbox and TB ECU etc etc....

The Imobbiliser then checks the transponder code from the key, and when the EWS unit confirms the correct key is inserted it allows the car to be started....

You then flick the key and the crank cycle is then initiated by the Engine ECU until the engine fires up....

If you are getting no response when you turn the key to position 2 (BCU to wake up the car) then it must be ignition switch related....

If the Transponder Coil wasn't working, it wouldn't allow you to turn the key as it wouldn't know there was a key inserted and unlock the ignition barrell...

Sometimes you don't even need to put the key in the switch to hear the solenoid click to unlock the ignition switch and steering coloumn...just holding the key near the coil is enough to trigger it off!

The only problem with it being the ignition switch is the fact I get no land rover logo on screen when I open the door , so this fault comes first which would indicate the problem lies in the bcu? Or am I being a bit blonde? I'm pretty sure the the transponder coil isn't powered up either because it should unlock the steering if the key is placed within 20mm of the key hole ( not inserted) this doesn't happen on clicking at all. Only when the key is placed in the ignition and turned to position 1 (won't go any further) then back again , wait 2.4secs then the key turns fully. Starts the car , land rover logo comes on , instruments etc. this back up procedure is described exactly in raves steering section upon k bus failure . It's just the fact that I get no land rover logo that makes me think the bcu is causing the k bus to fault?

paulvasey said:

The only problem with it being the ignition switch is the fact I get no land rover logo on screen when I open the door , so this fault comes first which would indicate the problem lies in the bcu? Or am I being a bit blonde? I'm pretty sure the the transponder coil isn't powered up either because it should unlock the steering if the key is placed within 20mm of the key hole ( not inserted) this doesn't happen on clicking at all. Only when the key is placed in the ignition and turned to position 1 (won't go any further) then back again , wait 2.4secs then the key turns fully. Starts the car , land rover logo comes on , instruments etc. this back up procedure is described exactly in raves steering section upon k bus failure . It's just the fact that I get no land rover logo that makes me think the bcu is causing the k bus to fault?

Click to expand...

I think you are almost right....the Unlock from the BCU is Hardwired to the Rear Doors and Tail and the Front Doors via the P Bus...so a fault on the K Bus will not prevent the unlocking...

The BCU then talks to the Instrument Pack, Immobiliser ECU and the Steering Lock ECU via the K Bus....

The Instrument Pack then talks to the Sat Nav unit via the I Bus...

So if the Instrument Pack isn't getting the Switch On signal from the BCU via the K Bus, it won't then talk to the Sat Nav and display the Logo via the I bus...

So I concur...K Bus Fault it is....

Now if the BCU is unlocking the vehicle via the Hardwired connections to the Rear Doors and Tail, and via the P Bus for the Front Doors....could we summise the BCU is indeed fine and is working OK?

The only other central Player in this is the Instrument Pack as all the other K Bus functions come from here....maybe this is playing up!

That being said, when you do the 'Emergency' 2.4 seconds ignition switch trick - do you have HEVAC control and Seat control?? as these systems rely on the K Bus signal..!!!

So BCU or Instrument pack could be at fault...not sure how to test without substitution!!

Mmm it's getting a bit clearer. But is it the instrument pack that wakes up the transponder coil ? Also i do have hevac after the emergency ignition trick I'm pretty sure I also have seat control although I'm not certain as I'm bit home at the mo. if it is indeed the instrument pack that wakes the transponder up at the same time as the screen then it would indeed point to an instrument pack problem. Is the pack plug and play? Or does it need activating by T4 or the like?

On my car it will let you turn on the ignition without the transponder chip in place

However it won't start or unlock the steering lock without the chip present

Does it do that on the first turn of the key? Or the second? It's not really relevant to my issues but I doubt that should happen if the steering lock is working correctly? The chip in key should surely match up with the transponder coil before it allows you to turn the key past position 1

as an update to my thread. i finally managed to clear all the faults after several battery disconections and hard resets and now may have the answer to problems, im getting an occasional 'key in ignition' message after i have turned off and removed the key. now if the vehicle thinks the key is still 'in' could this be the root cause of my k bus fault? and if so which ecu would decide this? the immobilisor or the steering colunm ecu?

paulvasey said:

as an update to my thread. i finally managed to clear all the faults after several battery disconections and hard resets and now may have the answer to problems, im getting an occasional 'key in ignition' message after i have turned off and removed the key. now if the vehicle thinks the key is still 'in' could this be the root cause of my k bus fault? and if so which ecu would decide this? the immobilisor or the steering colunm ecu?

Click to expand...

On the P38, key in ignition faults are due to the shutter in the lock not closing when the key is removed, it may be the same on the L322, graphite powder frees it all up nicely.

My ignition lock doesn't have a shutter, u don't know if this is normal for the l322? Or if there's one lower down?

paulvasey said:

My ignition lock doesn't have a shutter, u don't know if this is normal for the l322? Or if there's one lower down?

Click to expand...

Maybe it does but it's stuck where you can't see it, I'm sure my mates has one but Hippo or Saint would know for sure. It would soon fill with crap if there were no shutter.

Yer, you would think so! I'm a bit OCD though! No dust allowed in the motor!

Key In signal is from the transponder coil I would have thought or maybe the switch pack at the base of the barrell...

The ignition switch switch pack has been known to fail...maybe this is a sign!

mmm maybe one of you kind fellows could help eliminate one? as the transponder coil works by proximity (20mm i believe) if you turn off the vehicle and withdraw the key but rest it on top of the barrel then open the drivers door, if it is the transponder coil that gives the key in ignition message, you will get one. if not the message comes from the switch pack. simples

Give me ten to finish me sandwich and I'll let you know...never noticed a key in message before, but I'll give it a go