Strange Charging Issue
11-19-2013, 10:40 AM
#1
Super Member
Thread Starter
Strange Charging Issue
I am having a strange problem with my 2008 E320 Bluetec. While driving, the display will periodically change to a red battery symbol for a few seconds, then back to the normal display. This will happen repeatedly during a trip, but does seem to be more common in the first few minutes of driving.
What is odd is there is no warning text stating "battery - visit workshop" or similar. Just a red battery symbol with no words.
The main battery is a fresh, correct H8 AGM. It shows ~12.9v at rest, so is fully charged. Being a post facelift car, the bluetec does not have an aux battery under the hood, so don't go there.
I've not received any other electrical error messages, such as "convenience functions disabled", so we do appear to have enough juice. The car starts and runs fine.
I have pulled up the voltage display in the instrument cluster while driving. It's mostly stable at 14.2v. However, every so often it will go spastic and drop down to perhaps 12v and then recover back up to the normal 14.2v. I don't get the red battery display while in diag mode, I am guessing that diag mode preempts the error message display.
Has anybody seen anything like this before? It doesn't correlate to any of the problem descriptions I've read while searching about in the archives here. I am thinking it needs to go into a main dealer where they can evaluate the entire electrical system to identify the faulty component without scattershot replacement.
Any help or thoughts greatly appreciated.
What is odd is there is no warning text stating "battery - visit workshop" or similar. Just a red battery symbol with no words.
The main battery is a fresh, correct H8 AGM. It shows ~12.9v at rest, so is fully charged. Being a post facelift car, the bluetec does not have an aux battery under the hood, so don't go there.
I've not received any other electrical error messages, such as "convenience functions disabled", so we do appear to have enough juice. The car starts and runs fine.
I have pulled up the voltage display in the instrument cluster while driving. It's mostly stable at 14.2v. However, every so often it will go spastic and drop down to perhaps 12v and then recover back up to the normal 14.2v. I don't get the red battery display while in diag mode, I am guessing that diag mode preempts the error message display.
Has anybody seen anything like this before? It doesn't correlate to any of the problem descriptions I've read while searching about in the archives here. I am thinking it needs to go into a main dealer where they can evaluate the entire electrical system to identify the faulty component without scattershot replacement.
Any help or thoughts greatly appreciated.
11-19-2013, 01:27 PM
#2
I had this issue in my '07 Bluetec about 3 years ago when my vehicle was still under warranty. I would be driving for about 15-20 minutes when the red battery malfunction message would appear.
It took significant diagnostic time, and required the dealer to use the oscilloscope tool that is built-in to most STAR Diagnosis systems.
In brief, there was a short circuit between the low and high interior CAN circuits. Various sill trim panels were removed to access CAN diagnostic points and impedance and signal waveforms were checked at each one. Fault code DTC 9313 was present throughout and would not erase. The technician systematically removed devices from the interior CAN bus, and the fault went away when X30/7 (which is the Rear SAM) was disconnected. CAN connectors in to the rear SAM were inspected, and it was found that the CAN bus short circuit went away when connector # 18 was removed. The other connector, # 22 appeared to be OK.
"TRACED WIRES TO FIND SHORT WHERE WIRES ARE DAMAGED FROM CONTACT WITH SHARP METAL OF SUPPORT BRACKETS - SHORT CAUSES INTERMITTENT CAN COMMUNICATION FAULT EVEN THOUGH TRACES SHOW FAULT TO BE PRESENT AT ALL TIMES" after the wires were repaired, DTCs were cleared and did not come back.
Before this the dealer also tried replacing the alternator voltage regulator, but this obviously was not the root cause.
Good luck!
It took significant diagnostic time, and required the dealer to use the oscilloscope tool that is built-in to most STAR Diagnosis systems.
In brief, there was a short circuit between the low and high interior CAN circuits. Various sill trim panels were removed to access CAN diagnostic points and impedance and signal waveforms were checked at each one. Fault code DTC 9313 was present throughout and would not erase. The technician systematically removed devices from the interior CAN bus, and the fault went away when X30/7 (which is the Rear SAM) was disconnected. CAN connectors in to the rear SAM were inspected, and it was found that the CAN bus short circuit went away when connector # 18 was removed. The other connector, # 22 appeared to be OK.
"TRACED WIRES TO FIND SHORT WHERE WIRES ARE DAMAGED FROM CONTACT WITH SHARP METAL OF SUPPORT BRACKETS - SHORT CAUSES INTERMITTENT CAN COMMUNICATION FAULT EVEN THOUGH TRACES SHOW FAULT TO BE PRESENT AT ALL TIMES" after the wires were repaired, DTCs were cleared and did not come back.
Before this the dealer also tried replacing the alternator voltage regulator, but this obviously was not the root cause.
Good luck!
