P38 pulling .86 amps (I think) when ignition off

Have a problem starting last week, battery discharging overnight. Tried a different battery, still the same.

Put an ammeter between neg and frame, showing .86 amp discharge.

Tried pulling fuses and relays, still the same. Noticed when I touched neg lead to batt terminal I heard a click sound like a solonoid.

Traced the sound to panel, when I pulled the panel connector the click stopped (+ discharge) also noticed when disconnecting from battery terminal there was another fainter click, traced this to relay under passenger seat (I think this is airbag relay).

When this relay is disconnected from the base the discharge goes down to .45 amps.

I have had airbag warning light on for a number of years, so not concerned about this !

Any ideas pls !!!

Thanks for reading

Frank

Check the underbonnet fuse box for signs and smells of burning, check the BECM is going to sleep.

Thanks very much for the info. I have done some more research now (online) and think it is the BECM not shutting down.

Going to test again with my meter, I believe it should power down about two minutes after turning off the ignition. Hood and doors should be shut.

Thanks again.

Frank

Franco said:

Thanks very much for the info. I have done some more research now (online) and think it is the BECM not shutting down.

Going to test again with my meter, I believe it should power down about two minutes after turning off the ignition. Hood and doors should be shut.

Thanks again.

Frank

Click to expand...

If the BECM is not going to sleep, a likely cause is the RF receiver for the key FOB.
Your SRS message, do you have the side airbags in the seats?

Franco said:

Have a problem starting last week, battery discharging overnight. Tried a different battery, still the same.

Put an ammeter between neg and frame, showing .86 amp discharge.

Tried pulling fuses and relays, still the same. Noticed when I touched neg lead to batt terminal I heard a click sound like a solonoid.

Traced the sound to panel, when I pulled the panel connector the click stopped (+ discharge) also noticed when disconnecting from battery terminal there was another fainter click, traced this to relay under passenger seat (I think this is airbag relay).

When this relay is disconnected from the base the discharge goes down to .45 amps.

I have had airbag warning light on for a number of years, so not concerned about this !

Any ideas pls !!!

Thanks for reading

Frank

Click to expand...

The EAS delay relay is under passenger seat, If it is duff know problem for battery discharge on the diesel version.

Thanks for replies gentlemen.

Took a look late this afternoon. BECM does appear to be powering down, goes from .86 amp to .07 or .08 amp after two minuites or so, so still to high I think. Doors and Hood do not need to be closed to get a reading.

Also removed all fused one by one with no difference, no electrical smell from f/box.

My P38 is petrol & gas, remote locking deactivated, use central locking only.

I think at 0.07 amp discharge battery should be ok for a few days ??

So any further information would be appreciated.

Doors and tailgate need to be shut,but you can leave the bonnet open for BECM sleep tests.Depending on the type of LPG system its ecu can often take 80-100mA on its own,OR if its the type that takes its signal from pin 7 of the OBD socket it will just keep it awake.
Old tracker systems with dying NiCad batteries are a favourite - often well hidden.Mobile phone kits and extra driving lamps etc are other favourites for current drain too.

Disconnected the LPG supply appears to be tapped into a spare relay base via a spade
Connector, will look a bit further into this !

Had a good look under dash, have taken a number of power supplies etc out over the years, do not think there is anything left., but will certainly take another look.

A demo on U-tube said that all doors and bonnet need to be closed for the test. I did this initially and then found it seemed to power down even with the doors open !!

How long should a good battery last with a 800ma drain ??

Thanks for taking the time to reply.

Frank

Sorry should read 80mA drain.

Not very good with lecktrikcity but shouldn't it be possible to use the meter on each of the fuses one by one to see which is drawing the current?

Franco said:

Sorry should read 80mA drain.

Click to expand...

Disconnect the clock and alarm then. There has to be some drain to run the none sleeping systems.

The BECM should draw around 30ma when sleeping.

Hi

I'm reliably informed that the air bag warning light will constiute an MOT failure from next January. Unplug the yellow wires under both driver and passenger seats. Spray with contact fluid and replug. You could find that pesky fault light disappears. Mine did. Cheapest repair going.
Regards

DougK

Just an update where I am at the moment.

Battery was still charged this morning 12.4v started OK. Think I can live with this, do not know why it has changed from discharging in a night, must have been playing with it !!

Anyway took a look all round to see if there was any obsolete phone or other components, removed enough wire and fuse holders to rewire a ring main, still sitting on 80 mA when BECM powered down.

Now monitoring the battery voltage, presently at 12.56v, will take a look in the morning to see votage drop. Guess I will have to take into account V= IR, as voltage drops mA will increase. (I think).

Interesting point from DougK, my airbay light came on as a result of removing the fuse by mistake and will need to be reset by a dealer, (as far as I know) there is nothing wrong with the circuit, and I did not think it was possible to reset it any other way.

Really appreciate all comments and information given here.

Regards

Frank

Franco said:

Just an update where I am at the moment.

Battery was still charged this morning 12.4v started OK. Think I can live with this, do not know why it has changed from discharging in a night, must have been playing with it !!

Anyway took a look all round to see if there was any obsolete phone or other components, removed enough wire and fuse holders to rewire a ring main, still sitting on 80 mA when BECM powered down.

Now monitoring the battery voltage, presently at 12.56v, will take a look in the morning to see votage drop. Guess I will have to take into account V= IR, as voltage drops mA will increase. (I think).

Interesting point from DougK, my airbay light came on as a result of removing the fuse by mistake and will need to be reset by a dealer, (as far as I know) there is nothing wrong with the circuit, and I did not think it was possible to reset it any other way.

Really appreciate all comments and information given here.

Regards

Frank

Click to expand...

As the voltage drops the current should also drop if the circuit resistance remains constant Unless you have a very accurate DVM, a .4volt drop in battery voltage will produce a very small difference in the mA reading that you probably will not see. V over R = I