P38A 2.5 DHSE Electrical

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RangeRoller dt said:
My mate fitted a start stop. Couldnt work out why, still had to put key in and turn it?

Fancy smanchy diagnostics won’t usually talk to a P38, only specific ones do.
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The kit i have tells you to cut the actual key part off the fob, or use a spare key, insert the key body into the lock and leave it in the acc1 position. The box of tricks takes over from there. This kit is linked with the keyless entry kit and wont turn on the ignition until the doors have a valid unlock. If you leave the vehicle for more than a few mins with the ignition off, it resets itself and you then have to lock and unlock the vehicle to start it again.

My friend looks after a couple of other P38's and said he's not had an issue before. I wish i could remember the name of the kit he uses.
 
I did Google and see something about being able to turn on and off the interior light, i did have a quick play without luck, but i may have been doing it wrong. I will have another go tomorrow.
 
Jomac said:
I went to my friends garage and he has a professional OBD tablet costing some £2000+ He had a look to see if he could get the fob working. He couldn't see anything that remotely suggested the BECM, just general diagnostics, engine, transmission ABS etc. I don't know if its related but the interior lights dont work, puddle lights do
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You need dedicated diag like Nanocom. The petrols are only OBDII compliant engine wise and nothing on the diesel plays with OBDII.
 
Jomac said:
The kit i have tells you to cut the actual key part off the fob, or use a spare key, insert the key body into the lock and leave it in the acc1 position. The box of tricks takes over from there. This kit is linked with the keyless entry kit and wont turn on the ignition until the doors have a valid unlock. If you leave the vehicle for more than a few mins with the ignition off, it resets itself and you then have to lock and unlock the vehicle to start it again.

My friend looks after a couple of other P38's and said he's not had an issue before. I wish i could remember the name of the kit he uses.
Click to expand...

I am not sure how much you are fooling the BECM bit it will give an error message if you leave the key in the ignition and it may start having issues the central locking and asking for the EKA.
 
Grrrrrr said:
I am not sure how much you are fooling the BECM bit it will give an error message if you leave the key in the ignition and it may start having issues the central locking and asking for the EKA.
Click to expand...
+1 to that ^^^^^^^
As I said, a world of pain beckons if you don't have a clue how the BECM works. Sooner or later you will end up being locked out with the engine disabled.
 
A couple of very valid points here, one i had overlooked with the key in the ignition.

I tried metering the connections on the door lock assembly which didn't make much sense until i removed the door lock (Now wishing i hadn't.!!!). There are 7 wires going to the door lock, 3 for the motor. Inside the door lock are 3 micro switches which are normally closed in the rest position, ie no key in the door and the inside door button in the up position. When to put the key in the door and lock it, one microswitch goes open circuit briefly and then closes. To unlock, another microswitch opens briefly and then closes. The remote key unit i have, has 2 change over relays inside. I simply connected the normally closed contacts in series with the two normally closed switches in the door lock, so operating the new fob breaks the open close switch circuits in the same way the key does. The 3rd micro switch is connected to the interior door lock button and appears to only operate when the vehicle is locked and you try to unlock from inside.

As for the key in the ignition sensing, i will have to look a little closer at this, if its just a microswitch physically sensing the blade of the key, i might be able to get around that, but if the ignition lock actually senses the transponder chip in the key fob, it wont be so easy.

I'm trying to avoid forking out an arm and a leg in taking it to a RR garage. Would anyone know if there is a garage with the right kit to modify the BECM near me in Suffolk/Essex?
 
Jomac said:
A couple of very valid points here, one i had overlooked with the key in the ignition.

I tried metering the connections on the door lock assembly which didn't make much sense until i removed the door lock (Now wishing i hadn't.!!!). There are 7 wires going to the door lock, 3 for the motor. Inside the door lock are 3 micro switches which are normally closed in the rest position, ie no key in the door and the inside door button in the up position. When to put the key in the door and lock it, one microswitch goes open circuit briefly and then closes. To unlock, another microswitch opens briefly and then closes. The remote key unit i have, has 2 change over relays inside. I simply connected the normally closed contacts in series with the two normally closed switches in the door lock, so operating the new fob breaks the open close switch circuits in the same way the key does. The 3rd micro switch is connected to the interior door lock button and appears to only operate when the vehicle is locked and you try to unlock from inside.

As for the key in the ignition sensing, i will have to look a little closer at this, if its just a microswitch physically sensing the blade of the key, i might be able to get around that, but if the ignition lock actually senses the transponder chip in the key fob, it wont be so easy.

I'm trying to avoid forking out an arm and a leg in taking it to a RR garage. Would anyone know if there is a garage with the right kit to modify the BECM near me in Suffolk/Essex?
Click to expand...

I really do think you need to start listening. Repair the standard fitment.
 
Jomac said:
A couple of very valid points here, one i had overlooked with the key in the ignition.

I tried metering the connections on the door lock assembly which didn't make much sense until i removed the door lock (Now wishing i hadn't.!!!). There are 7 wires going to the door lock, 3 for the motor. Inside the door lock are 3 micro switches which are normally closed in the rest position, ie no key in the door and the inside door button in the up position. When to put the key in the door and lock it, one microswitch goes open circuit briefly and then closes. To unlock, another microswitch opens briefly and then closes. The remote key unit i have, has 2 change over relays inside. I simply connected the normally closed contacts in series with the two normally closed switches in the door lock, so operating the new fob breaks the open close switch circuits in the same way the key does. The 3rd micro switch is connected to the interior door lock button and appears to only operate when the vehicle is locked and you try to unlock from inside.

As for the key in the ignition sensing, i will have to look a little closer at this, if its just a microswitch physically sensing the blade of the key, i might be able to get around that, but if the ignition lock actually senses the transponder chip in the key fob, it wont be so easy.

I'm trying to avoid forking out an arm and a leg in taking it to a RR garage. Would anyone know if there is a garage with the right kit to modify the BECM near me in Suffolk/Essex?[/QUOTE]
Click to expand...
 
Jomac said:
A couple of very valid points here, one i had overlooked with the key in the ignition.

I tried metering the connections on the door lock assembly which didn't make much sense until i removed the door lock (Now wishing i hadn't.!!!). There are 7 wires going to the door lock, 3 for the motor. Inside the door lock are 3 micro switches which are normally closed in the rest position, ie no key in the door and the inside door button in the up position. When to put the key in the door and lock it, one microswitch goes open circuit briefly and then closes. To unlock, another microswitch opens briefly and then closes. The remote key unit i have, has 2 change over relays inside. I simply connected the normally closed contacts in series with the two normally closed switches in the door lock, so operating the new fob breaks the open close switch circuits in the same way the key does. The 3rd micro switch is connected to the interior door lock button and appears to only operate when the vehicle is locked and you try to unlock from inside.

As for the key in the ignition sensing, i will have to look a little closer at this, if its just a microswitch physically sensing the blade of the key, i might be able to get around that, but if the ignition lock actually senses the transponder chip in the key fob, it wont be so easy.

I'm trying to avoid forking out an arm and a leg in taking it to a RR garage. Would anyone know if there is a garage with the right kit to modify the BECM near me in Suffolk/Essex?
Click to expand...

Most garages don't even know how to get the diagnostics right on a car this old. Rick-the-pick on here has a business in Sussex that fixes BECMs. He's the only person to trust with it.

Yes, ignition has microswitch. Later models have a passive coil to sync fob and BECM with thr rolling security code added to the unique code from the key. Details are in the security section in RAVE. Note the EKA is not the same as the engine immobilisation code, that's another arm of the security setup.

There are 3 microswtches. Among other things it allows the car to know how the EKA is being entered. The boot button grounds through the centre one so that one tends to burn out.

The unlock motors are massively too small to take a full hit of current so only a pulse is sent and that pulse spins them so fast they have enough momentum to pop the locks.
 
I am listening to all comments and heeding advice. I come from a strong electronics background and program custom micro's as part of my living, so i am on familiar territory here. The kit i am fitting is a two part kit, keyless entry and keyless ignition. Unless i can get a valid logic signal from the BECM that says doors are unlocked, i have to go with the keyless fob system which is designed to work with the keyless ignition. I am very familiar with Canbus protocols having done a few projects in the past on the Jaguar cars i have owned. I really am listening to all of the comments, my weak area is not being (for the moment) familiar with the electrical layout of the RR
 
When you have put the BECM into an alarmed state a few times, costing £200.00 or £300.00 a time to have corrected you may think your mods are without merit. Repair the standard systems.
 
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