Hi All,

I've just had the valve cover gaskets and PVC breathers replaced on the car and within 200 yards from the garage the engine management light came on.

I took it straight back and they had a great deal of trouble reading the ECUs with two different Snap On diagnostics kits. They did manage to read it in a generic mode and found no fault codes.

I'm hoping it's something benign such as the fuelling now being off the long term map due to the breather system now working correctly.

Another mechanic had problems using their diagnostics on the car too, just after the LPG was installed and the EML came on after a slight misfire.

I've got myself an iCarsoft i930 which is Jaguar / Land Rover specific, as well as a generic reader.

This can read every system in the car without any problem, with the exception of the Engine ECU which reports back a comms fault. Ignition off / on / engine running makes no difference.

Could it be a battery issue not providing enough power? The battery is rather tired and there were a number of low voltage DTCs stored in various ECUs. Or could it be the install of the LPG ECU causing comms problems?


Cheers





Clive

Last edited by destructimo on 20th Jun 2015 7:05pm. Edited 1 time in total

Hi all,

Had another fiddle last night and it can't read the headlight leveling ECU either. Could this possibly be the culprit and how do I get at it to check?


Cheers





Clive

do you have the engine running and is it pushing out around 14 volts when you check the diagnostics .. ... - .- -.




Y. O. L. O.
.

Hi Stan,

From memory it was 14.1V with the engine off or 15V with the engine running according to the i930 tool. I haven't done a test with a multi meter on the battery yet.

I've tried it ignition off, ignition on and also engine running without success on the engine or headlight leveling ECUs.


Cheers





Clive

sounds what you are doing is ok...low battery power results in some ecu's not being available to the diagnostic tool..

i dont know why you cant get the headlamp ecu ,maybe a battery disconnection will reset everything..

...or scrap what you have and get a GAP iidtool.. ... - .- -.




Y. O. L. O.
.

My drivers side headlight ECU stops my IIDtool working as it can not read past the headlight ECU but if I just disconnect it I can read all the other ECU's no problem and I also get a nice message to say the headlight ECU is not responding so this might be worth a try for you. The ECU is at the back of the headlight and is a bit fiddly to unplug. 2010 3.6TDV8 Stornoway Grey/ Black interior - gone
2005 4.4V8 (M62) Bonatti Grey/ Parchment interior - gone
1998 4.6HSE Blue/ Cream interior (can't remember exact colours) - gone
1977 White - gone (should have kept)

Not had any time to play with this any further but I have just connected the battery charger and it's showing the battery as 50% charged at 12.4V and that's after just using the car, so maybe a voltage problem after all.

I will check in the morning.


Cheers





Clive

Turn off the LPG system, maybe even need to pull the fuse!!!

Find lots of FF’s that won’t respond whilst on LPG! Don’t know why but a fact worth investigating...

I have your answer Craig.

After taking it back to the Garage they fiddled about and shrugged their shoulders, as did the main dealer this week. In the end I gave the LPG installer a call in the week and he said 'no problem at all' and he popped round this afternoon.

Apparently some LPG installers (mine included) fit some electrical gubbinsery to the OBDII port to prevent erroneous EML activations. Sometimes this can interrupt the comms to the engine ECU. He disconnected the doo dah and comms worked perfectly with his tool and my own cheapo jobbie.

Fault is a defunct o2 sensor, so he's going to fit a new one for me and also see about putting the doo dah on a switch so next time it won't be a faff about taking the OBDII port out of the fascia.

At lest the comms issue is solved. I hope that helps someone out.


Cheers





Clive

Hi All,

Just a quick update.

New o2 sensor fitted this morning and engine light off. Happy days.

I also showed him something that had been bothering me for a while 'the sound of air sucking when blipping the throttle from idle'. He had a quick listen and then plugged in his diagnostics again to get a live feed from the MAF sensor which was playing up.

New MAF ordered today and I'll bung that in tomorrow and it should be plain sailing again.


Cheers





Clive

That do-da is a device to reset the fuel trims every time you restart the car, they used to fit a relay to, in effect, disconnect the battery every time you started....

Fitted by LPG installers who don't know how to set the system up properly........  Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

I think this one gives the petrol ECU a compensated reading from the o2 sensors when running on LPG so the petrol ECU doesn't get confused and cause an incorrect mixture when it switches back to petrol.


Cheers





Clive

If it needs to send a compensated reading then it's not tuned right... when you tune an LPG system you tune it to keep the STFT within range then you know it's not running lean or rich.... along with lambda cycling... Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-

The LPG system is set up fine. Nigh on 14,000 miles on it now without a hitch.

It's an interesting point you make though.

As far as I understand it LPG and Petrol have different ideal air/fuel ratios. So when it's running on LPG the petrol ECU sees the wrong mixture at the o2 sensors and adjusts it's fuelling accordingly which does nothing because the fuelling is being controlled by the LPG ECU, until eventually it goes outside it's parameters and throws an error code and EML. For it not to do this without compensation then the LPG fuelling would have to be trimmed in the map to provide a mixture that the petrol ECU was happy with.

I'm no expert though. Just happy to make progress with the list of little niggling jobs on the car.


Cheers





Clive

Yes, your right to a point, the stoichiometric air/fuel ratio of petrol is 14.7:1 LPG is 15.5:1 so not that different but that doesn't make any difference to how a closed loop system works, the lambda is looking for unburnt fuel, it doesn't measure the ratio, when it see's the mixture is rich it sends back a high reading and the mixture is leaned off until it gets too lean then richens it... it sort of yo-yo's...

The LPG ECU "steals" the injector opening times from the vehicle ECU and adds around 20% to their times (this is because the calorific value of LPG is lower than petrol) so the LPG is directly controlled by the lambda talking to the vehicle ECU.

An experienced LPG tuner can adjust the 20% factor to suit the characteristics of the engine and improve power and economy and keep the fuel trims very tight...

It is easy to make an engine run on LPG and with a clever box to stop the MIL coming on when it is running rich you won't notice any difference, but it will be running rich, wasting fuel and be down on power. Pete

__________________________________________________
2014 L405 Autobiography SDV8 4.4 Loire Blue Ebony interior
2011 L322 Vogue SE 4.4 TDV8 Baltic Blue. Parchment over Navy Interior. Sold
2012 L322 Autobiography 5.0 Supercharged Ipanema Sand, Jet Interior. Sold
2002 L322 Vogue 4.4 V8 Epson Green, Ivory over Aspen Interior (Fatty Offroader) Sold
-Click for Project Fatty off roader-