Newbie - C5 2011 electrical issues

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C5-NON
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Newbie - C5 2011 electrical issues

Unread post by C5-NON »

Hello all,

Newbie here. Bought a C5 2011 Estate, mechanically it is driving great, however i have some electrical issues i was hoping someone may know how to fix.

1) Had battery charging fault indicator, however car never lost charge, checked alternator was fine, however changed battery for a brand new one anyway, same fault, so disconnected the battery monitoring cable on the negative battery terminal, now that fault has gone (hence probably is the battery monitoring component that is faulty?). However i have always had these other faults since owning it as below, so wonder about the relationships

2) Speedo needle is always around 10-20 mph out, however digital speed seems correct
3) rpm needle seems out (3k rpm at 70 mph?, should it be nearer 2k?)
4) Fuel gauge needle always showing empty, however the digital read out seems to be operating normal and showing miles left to empty etc..
5) Radio/nav system seems to lose the time and date memory now and again after leaving the car the night, remembers my phone ok though?
6) Drivers mirror doesn't always recline when locked

I have tried BSI reset, no change to anything.

I assume all could be related to the BSI or BSM from what i have read online, but not sure if i could just have a faulty speedo cluster and fuel level sensor, not sure about the radio and door mirror however?

As i say, the car runs fine and is totally useable, but would like to sort these electrical faults out, any ideas??

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GiveMeABreak
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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

First of all are you saying you removed the Battery Charge Status Unit that looks like this?:
BCSU.PNG
BCSU B.PNG
BCSU B.PNG (165.02 KiB) Viewed 162 times
If so, I would suggest you change the BSI configuration to put control of the energy management back to the BSI from the BCSU, or you could end up with a car that won't start. The BCSU undertakes various monitoring functions of the battery's state, including temperature and this information is used to manage the energy saving features of the vehicle. By taking the BCSU off without handing control of this function back over to the BSI which provides a more simplified timed use of accessories you are leaving yourself with open to a flat battery and unable to start the car. See my post here on how to do this:

viewtopic.php?t=60776

I think a lot of these other problems may be related to the electrical system. The fact that your Nav system is not retaining date and time settings indicates power loss. If it is still doing it now, with a new battery, you still have a fault in the charging circuit somewhere I suspect, possibly wiring, but don't overlook the possibility of a faulty alternator or wiring from the alternator. You could well be running the car from the new battery alone this will soon die too. If your power steering starts getting intermittently heavy (assuming you have the electro pump) that's another sign your battery is not getting charged.

C5s and modern cars in general have a stack of electronics on board and anywhere in excess of 20 ECUs. A poor / weak battery will wreak havoc on electrical systems and can cause a multitude of faults that you may not think are related. An example - your fuel gauge - information is read 15 seconds after the vehicle ignition is switched off and recorded. The next time the vehicle is started, the BSI takes a fuel measurement and if the measured value is different from the value saved the last time the ignition was turned off, it deduces that the fuel tank has been refilled and the new volume of fuel is recognised.

If both values are identical, the BSI takes the last fuel value displayed on the instrument panel. So if you are having electrical interruptions on the data networks it may result in data not being recorded or the system operating properly - and I would suggest similar for the speedo and rev counter readings - these all rely on interactions between the ESP ECU the engine ECU and the BSI.

And before you do any battery disconnection / reconnection follow the procedure:

BSI Reset / Battery Disconnect / Reconnect Procedure

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Re: Newbie - C5 2011 electrical issues

Unread post by C5-NON »

Thanks for the reply,

yes i just disconnected the plug to the BCSU , can these go faulty?

1) I have seen on the car, that the time and date only reset if the "coordinate time from GPS" tickbox is checked, otherwise it seems to hold the memory
2) I have had a multi-meter across the alternator, seems to be in correct range when running 13.8V ( i believe normal range is 13.5v - 14.v volts) this is a brand new battery so lower value is normal i think.
3) I tried the resistance across the fuel sender terminals, i only got 1.5 ohms after putting £30 of diesel in, i am sure this value seems to low? would you know the normal ohm range for the Fuel sender?
4) Could it possible the BSI is faulty? does this unit control the manual speed and rpm needles?
5) Where is the best place to obtain the fault reading software and digibox?

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GiveMeABreak
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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

The BCSU paret number was updated, which indicates a replacement part at some point.

As far as the Sat Nav goes - I'm assuming you have the MyWay. You need to leave that check box unticked, because of the GPS Week Number Rollover issue:

"To provide the current date, the Global Positioning System (GPS) keeps an internal count of the number of weeks since January 5, 1980. The main civil GPS signal (C/A code) broadcasts the GPS week number using a 10-bit code with a maximum value of 1,023 weeks. This means every 19.7 years, the GPS week number in the C/A code rolls over to zero. This occurred for the first time in August 1999.

The GPS week number again reset to zero at 23:59:42 UTC on April 6, 2019. Many GPS-enabled devices that were not properly designed to account for the rollover event exhibited problems on that date. Other equipment became faulty several months before or after that date, requiring software or firmware patches to restore their function."

As far as the MyWay RNEG system is concerned, this can result in incorrect operation and the recommendation to avoid this is to uncheck the synchronise with GPS option. Of course it won't then Synch the time- but that is better than being directed to the North Sea! Later systems will use 13 bit code which will solve the problem.

I think you may have a fault on one of your data networks - as the instrument panel communicates with various other ECUs to display the information.

An example of the Fuel Gauge: if there is a network error or an invalid fault received by the instrument panel, it will display the last value it received for a period of 5 seconds. Then after the 5 seconds it will go back to rest.

The same happens to the rev and speed counters - although you are saying these are working but not correctly.

You really need to get it diagnosed with Diagbox and report back any fault codes. As for the Ohms for the fuel level - there are tests that can be undertaken using Diagbox that will assist with this.

Myself and other members here have bought their Diagnostic kit from Easydiagnostcs.

They are UK based and have a good reputation here, and provide support.

We are not affiliated, but there is an FCF member discount available - details here:

viewtopic.php?t=60113

C5-NON
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Re: Newbie - C5 2011 electrical issues

Unread post by C5-NON »

I have plugged the car into diagnostics today, had communication error with the BCSU intermittently so I assume that is faulty. I also did self tests on the speedo,Rev,fuel counters. Rev counter has reset to normal, speedo still sits at 80mph when stationary but does move, the fuel gauge did not move at all under test. Hence I figure I have a mechanical failure of the gauges, and also a faulty BCSU, would you agree?

If I swapped the instrument panel would it take mileage from BSI?

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Re: Newbie - C5 2011 electrical issues

Unread post by wheeler »

C5-NON wrote:
30 May 2020, 17:13


If I swapped the instrument panel would it take mileage from BSI?
If you fit an instrument panel with a lower mileage than yours the BSI will write your higher mileage to the 'new' panel.
If you fit a panel with a higher mileage than yours your BSI will permanently inherit the higher mileage of the new panel even if you swap it back again.

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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

C5-NON wrote:
30 May 2020, 17:13
I have plugged the car into diagnostics today, had communication error with the BCSU intermittently so I assume that is faulty. I also did self tests on the speedo,Rev,fuel counters. Rev counter has reset to normal, speedo still sits at 80mph when stationary but does move, the fuel gauge did not move at all under test. Hence I figure I have a mechanical failure of the gauges, and also a faulty BCSU, would you agree?

If I swapped the instrument panel would it take mileage from BSI?
Be aware that the BCSU takes measurements of the battery periodically - so it not an on or off device as such, so I'm not sure that you will be able to determine if it is working correctly or not.

The battery charge warning light comes on in the following cases:
  • Battery charge status below 50% (Only during the vehicle’s first 20 kilometres)
  • Battery voltage higher than 16 V for more than 3 minutes
  • Battery voltage lower than 12 V for more than 3 minute
It has the following role:
  • Autodiagnostics reporting any faults detected on the sensors and/or internal electronics of the battery charge status unit.
  • Storing of the minimum current consumed on the 12V network when the vehicle is on standby.
  • Detection of crossing of an ancillaries battery charge threshold every 10 % with triggering of the built-in systems interface BSI.
  • Making the measured physical quantities available (Voltage, current and temperature of the ancillaries battery).
  • Detection of disconnection of the ancillaries battery.
... and these functions:
  • To allow an operator to quickly identify a failure on the battery charge status unit and/or the ancillaries battery.
  • To detect an abnormal and continuous consumption on the 12 V network when the vehicle is on standby.
  • To allow the built-in systems interface to memorise the context associated with the discharging of the ancillaries battery.
  • To give access to the information measured by the sensor in order to assist in checking or diagnosing certain units.
  • To permit checking of the ancillaries battery charge status before storing the vehicle in park mode.

C5-NON
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Re: Newbie - C5 2011 electrical issues

Unread post by C5-NON »

Under test with diagbox connected, the voltage stays steady at around 12.4V, however the battery status warning still comes on, however first try diagbox would communicate with the BCSU, how now it’s saying communication fault. And also was reading the alternator excitation voltage as 0. This cannot be correct as battery definitely charges as been on a few long journeys and isn’t losing charge. So I assume the BCSU is not reading the voltage correctly?. Can I ask when you have the diagbox connected are you getting a voltage readout for the alternator excitation?

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GiveMeABreak
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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

I really need to know which engine you have - please pop your VIN up (auto-masked from public view).

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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

The battery warning light will come on if the battery charge status is 50% or under - so it's not just about what it reads in terms of its power output. As the battery charges up over time this will increase.

As you have Diagbox, can you confirm you have run a full Global Test and if so what if any fault codes were returned Paul. If there is a fault with the BCSU then it should report a current sensing, temperature or voltage sensing fault code.

You also mentioned you had a new battery. Can you confirm the capacity of the new battery in Amps? If this is different to the original battery type in Amps, then the BCSU needs to be configured to one of t he 3 values allowed using Diagbox.

I suggest you run the Global Test first and see what if any faults are coming up - don't interrupt the test - let it finish.

Put up any faults you get.

Also, you can use Diagbox to test the BCSU. Just go into parameters and select the appropriate tests, or after the Global test, select the BCSU form the list of ECUs on the list, confirm and this should take you to another menu that will list test parameters and configuration. This is where you would change the battery capacity if it is larger or smaller than the original - but it should not be smaller than the recommended.

Under the parameter tests, you should be able to read things like thge battery voltage, battery current, temperature, charge status, accuracy of the charge status value, and the type of battery connected in terms of Amps/hour etc.

Here are the values: (you will need to click the image to clarify & magnify it)
BCSU Values.PNG
(*) For the battery current display, it is very important to use the correct current scale when reading the battery current as an incorrect scale does not provide the correct battery current value.

C5-NON
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Re: Newbie - C5 2011 electrical issues

Unread post by C5-NON »

Hi thanks,

I didn’t realise you had to change the battery in the parameters. So it’s easy enough to change?

The new one is 80Ah 740A

The old one was 62Ah 540A

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GiveMeABreak
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Re: Newbie - C5 2011 electrical issues

Unread post by GiveMeABreak »

Well the old battery was wrong to start with and well below par!

Originally this vehicle was fitted with a 70Ah / 760A battery.
Then it was replaced with an updated 75Ah /800A battery.

Both are Level 3 batteries and this is what should be selected in the BCSU parameters. It could be that you are getting the incorrect reporting of the battery condition as the BCSU thinks the battery is at a higher capacity than what was fitted.....

The BCSU needs to know the correct battery type or it will be making the wrong calculations and assumptions and all the consequences that would follow regarding energy management.

So first thing I would do is check the battery parameters and see what it is set to.

Next, I would take the battery off the car and give it a full charge, refit it and leave the BCSU to settle with it and see what that does.

Always follow the guidance when disconnecting and reconnecting the battery or you can get electrical issues:

BSI Reset / Battery Disconnect / Reconnect Procedure

C5-NON
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Re: Newbie - C5 2011 electrical issues

Unread post by C5-NON »

I have purchased a new BCSU and fitted it, car now recognises it, and so far i have not got battery charge warning indication (going on long drive tomorrow though so will test it properly i guess). However when in diagbox, under test - says ECU not recognised after global test, although i actually can read the BSCU now (i can select between two versions however? i assume one is later, but what year car?, i seem to be able to select either and get readings however) .

I have two fault codes

FFF1 Battery charge status unit - voltage sensor fault
FFFE Battery charge status unit - configuration

I found a screen that states i have a 75AH battery, although i have a 80AH fitted, wonder if this could be the reasons for codes? - although i have tried to find the screen to change battery/register, cant seem to find it?

any ideas?


speedo and fuel gauge still not working correctly, although rpm is now after i reset in BSI. - i still think these have failed mechanically ?