Supply Voltage Issues with Driving
 

Hi,

I have read a few posts on this being related to the final stage relay (assuming the heater blower, unless there is another one in the car someone).....or the alternator wiring. Was trying to see if there were anymore clues in the logs I just got.

It has happened a couple of times in the last couple of weeks, but driving along I get the numplate error late, followed by the nav screen going black, radio stopping and then the trans failsafe.....the car goes for a little, but then doesn't want to anymore (it was fun getting my mum to jump behind the wheel to manoevre as I pushed, with limited brakes and no power steering). Last time it happened, the battery drained fully, road side assistance jumped it and said the battery and alternatore tested fine.

Will try and attach the INPA error and memory logs (I reset and jumped it again, but error came back this time and have dumped it on the side of the road).

Thanks heaps!

attached (I think)

Have you checked all the battery connections, including the bulkhead connector at the B+ jumper on the firewall and the connection of the smaller red cable to the batery terminal?

This has the hallmarks of a lose connection somewhere...

Do you have a scanner that will run live data?
I'd check to see what your alternator output is and do a battery check.

@ahlem - The road side mechanic checked these with a scanner, albeit when the gremlins disappeared - it sat there for a few hours before they could get there last time. Will see if it starts tomorrow and will check again.

@wpoll - will try and find these connections when I get the car back home. Where is this b jumper you mentioned?


Thanks!

An intermittently failing alternator will often give the "trans failsafe prog" error.

I'd also think, as @wpoll says, a faulty connection somewhere could do that.

Whatever you have seems to be intermittent. So any tests that show no problems should be ignored if made when the problem was gone.

A voltmeter, with yourself being ready to use it when the problem appears, will probably be better than reading codes. An OBD2 reader to measure system voltage, or (if you have the high cluster) reading voltage through the panel, will probably give clues.

Not sure what engine you have but once my power steering reservoir lines on my M54 were leaking. Directly on the alternator. This gave me intermittent trans fail safe errors.

Thanks. It is an N62 4.4. I know they leak at the alternator bracket, so it could also be a source of unwanted fluids. Will be heading back to the side of the road shortly to see how it is.

The only other thing to note is that the battery is drained very quickly.

The image below is used a lot here and it's not 100% accurrate for all models but it gives you the genberal idea...

There are at least two connections that might cause your problem. One is the "Battery Safety Terminal" (BST) on the positive battery lead (along with the smaller red battery cable bolted to the side of the BST).

Another possible problem location is at the positive jumper connection under the hood (bonnet) - it can get loose and disconnect the battery.

It's labelled "THRU BULKHEAD UNION SPLICE" in the image below.

(NOTE: The image shows the B+ terminal as a separate line but in many E53 X5s, it is at the union splice location)

https://xoutpost.com/attachments/x5-...ns-diagram.jpg

Hope that helps... :thumbup: