All Things V6...

[DHallworth]

No idea, will go and have a peak in a minute.

David.

[DHallworth]

Simon, It looks like you were right... the fault could be related to the gearbox! When the RR does that it's usually just a low battery voltage upsetting things!

There are two faults on the gearbox ECU:

Permanent Fault
ECU

Remote Fault
Permanent Fault
CAN Engine Torque Information

When viewing the parameters in the gearbox ECU the readings don't change when the car is just turning over. When the car splutters and tries to start you get a reading on the gearbox parameters.

If I clear the faults the Lexia says that the faults are cleared but the screen immediately shouts "Gearbox Fault". Going back to the Lexia it says the Remote Fault is back again. That's without even trying to crank the car!

This is bizarre. It was running beautifully the other night, I switched it off, left it over night, went back to it the next day and it won't start! Argh!

David.

[Mandrake]

Hmm odd indeed. The Engine torque information error suggests that the two ECU's aren't talking to each other properly over the CAN bus ? (The gearbox is not receiving the calculated torque figure from the engine...)

But you can interrogate both ECU's individually with the Lexia, right ? Sounds like a wiring problem to me...low voltage to either ECU or poor connections between them...

The fact that the RPM signal as read by the gearbox reads zero while cranking but jumps up when it tries to start suggests there could be a wiring break or bad connection that is being affected by the vibration and torquing of the engine.

Another possibility is one of the ECU's has got a bit confused by cranking with a flat battery and needs resetting...

I would try cleaning up the pins on the engine ECU connector first with some contact cleaner, then leave the battery off for half an hour to do a full ECU reset. If still no joy clean the connector on the gearbox ECU as well, although if its anything like the Xantia its a pain to get to...!

[DHallworth]

I cleaned the connector going into the ECU but not the one going into the gearbox.

Will get a better look at it tomorrow. Am off all of next week before heading to Wetherby so will try and get a look at it then. This is the last thing I need as I need it off the bloody ramp!

Ben, thanks for your offer. My dad's got a 406 Coupe with the same engine in it so I'll get some readings off that. Don't want to put you out

Edit: Yea I can interrogate both ECU's individually.

[Mandrake]

Some more thoughts David,

Has the car actually started since you replaced the radiator hose and filled up the coolant etc ? If not a pinched or intermittent wire in the wiring loom seems like a strong possibility, although I would try a full battery off reset procedure first.

The fact that it immediately came back with the remote fault logged in the gearbox tells us that the gearbox is not receiving data from the engine, which as far as the gearbox is concerned is an extremely critical problem.

It needs to receive engine rpm, without which it can't measure the slip of the torque converter (it only measures the output side of the torque converter for itself and relies on the data from the engine for the input side) or know what engine rpm is for gear changes etc.

It needs the torque figure also to help regulate torque converter clutch slip as well as decide how much pressure to apply to the various clutches. (Clutch hydraulic pressure is nearly doubled for torque above 230Nm on a 4HP20) It also receives the throttle opening percentage and engine load (MAP sensor reading) from the engine to help decide on gear changes etc..

In short without that data it wouldn't work in anything other than hydraulic 3rd emergency mode. Normally if the gearbox ECU failed the gearbox would go into 3rd emergency mode but the engine would still run, just as mine did when I took out the gearbox fuse.

The gearbox does have the power to shut down the injectors on the engine and/or severely retard the ignition in case of a serious fault such as not receiving engine rpm, is it possible that only some of the communication lines between the ECU are not working but the ones that allow the gearbox to command the engine are still working ?

I propose a test - remove the gearbox fuse, clear any faults on all the other ECU's and see if it will start. I have a hunch that it will...

Also when you scan all the other ECU's on the car, do any others report "remote" faults ? Remote faults are due to faults in other ECU's or a failure to communicate with other ECU's... see if any other ECU's report CAN bus related errors... maybe one of the CAN bus wires is shorted to earth somewhere... The Lexia doesn't necessarily use the CAN bus to communicate with ECU's depending on the year of the car, I think on earlier C5's the CAN bus is only used for inter-ECU communication, not interrogation by the Lexia.

[DHallworth]

Thanks Simon.

The battery is flat at the moment due to cranking and monitoring with Lexia. Will get it charged tomorrow and see what's going on.

David.

[KP]

Even when charged up David i would get some heavy gauge jumper cables off something like the RR to ensure a large power source is there to help keep the power up.
The RR excels at this when running, especially the modern 4.4tdv8's as the alternators push out a bit more power now and the AGM batteries charge back up quickly enough.

[DHallworth]

Will, there's no chance I'm running jump leads off the 4.4 TDV8...

I'll use one of the P38's if needs be but the Bosch Silver battery on the C5 holds it's charge pretty well. I've got a feeling something has assisted it in going flat by draining it though.

Simon, the car was running for over an hour after I fitted the new pipes and radiator. I stopped it and started it again a couple of times within that hour. It was starting, stopping and running without fault. It was only after being left over night after it had been running that it wouldn't start again.

Am going to go and do the BSI reset procedure on it in a minute and see what's going on.

Does anyone know which wires the ECU's use to talk to each other on the CANbus system?

I'll go and Lexia all the other ECU's in a minute and see what's going on with them as well.

David.

[KP]

I guess the newer ones are a bit more of a pain without their dedicated jump lead mounts

They are great vehicles to jump from as they have built in battery protection and the systems dont half get another vehicle upto starting charge quickly

[DHallworth]

I've never even looked under the bonnet on this one to notice that the jump points were missing! It's just had it's first service at 2300 miles. I've got the C5 battery on an 8amp charge just now so shouldn't take long to get juiced up again.

I tried starting it with a jump pack on it and just got an anti theft device fault.

Something has really pissed this thing off!

David.

[Ben82]

I tried starting it with a jump pack on it and just got an anti theft device fault.

Could be lack of battery juice between the jump pack and battery..... if not, do you have the confidential code to re-pair the keys with the lexia? Just incase

[DHallworth]

Ben, is that they key code? When I turn the key in the lock the indicators still flash etc so I don't think it's lost the code.

I'll give the dealer a call just now and get it just in case

David.

[Ben82]

Ben, is that they key code? When I turn the key in the lock the indicators still flash etc so I don't think it's lost the code.

I'll give the dealer a call just now and get it just in case

David.

Yup there are two....
A mechanical key code which is about 7 digits long (all numeric i think), for cutting the keys.... and
a 4 digit (alpha numeric) which is the confidential code for pairing keys with the car using a Lexia.

[DHallworth]

Right, got the code now anyway.

I really don't know where to start with this one tbh. I've never experienced any faults on a multiplexed car before.

Thinking back to when it was on the Lexia I could see all the ECU's and they were all communicating with the Lexia which suggests that they were ok in standalone mode however from memory all of them had faults on them which they didn't when I originally scanned it at Luke's so I'm guessing that they've all got remote faults on them now.

I've checked the handbook and can't see any central fuse that relates to the CANbus system or the multiplexing system so that rules that out.

What is the proper BSI reset procedure on these things?

Am I right in thinking it's the BSI that everything reports into?

David.

[Ben82]

David,

Over here for the long winded process of the BSI reset... I did most of it barring shorting the cables through a resistance (or otherwise). I guess that just ensures complete drainage of power.