The red battery visit workshop warning message came up on our 2006 E350. In the past, this was solved by replacing the aux battery.
This time, replacing the aux battery didn’t solve the problem. I thought the battery relay was bad and replaced it.
The current DTCs I’m getting are:
BCM:
9092 Component G1/7 (Auxiliary battery) is defective or not installed. (stored and current)
9071 Component K57/2 (Auxiliary battery relay) or the signal wire to the component is faulty. (stored)
On board electrical system(voltage supply):
9092 Component G1/7 (Auxiliary battery) is defective or not installed. (stored and current)
9071 Component K57/2 (Auxiliary battery relay) or the signal wire to the component is faulty. (stored)
System diagnosis(CAN):
9309 The control module has not yet been programmed with the knowledge base. (stored and current)
Does this imply either the BCM or alternator are bad (or something else)?
Does the new relay need to be programmed?
Any thoughts on how to proceed?
Hi,
Please reinspect the wires to the aux battery that you installed. It is not uncommon for the + or - wires to disconnect during installation which keeps the error message on. Another thing you need to do is to access the aux battery and measure voltage. Even if it was a new battery if it had been sitting on the shelf it may have discharged and now the car does not see it showing you the error message. The issue with the aux battery is that Mercedes are known to not charge those as well as the main battery. If the car sees the aux battery voltage is too low it stops sending a charge to it completly.
Let us know what you find out.
Trying to troubleshoot before posting this, I charged both the main and aux batteries. The aux battery showed 12.9V and the main was 12.5V. When I started the engine, the aux battery voltage showed 12.9V and the main battery showed 14.3V. Based on this, I replaced the relay; that didn’t fix the problem.
The big wires to the aux battery from the relay are a little hidden but as far as I can tell are intact from the relay to the battery and the connections are tight. I have no idea what the condition of the control circuit wires is, these are the ones from the battery control module to the relay.
Hi, It seems like the issue is with the auxiliary battery, its relay, or the wiring. The codes suggest the battery might not be properly installed or the relay is faulty. Since you’ve replaced the relay, double-check the wiring and make sure the new auxiliary battery is fully installed and charged. The relay usually doesn’t need programming, but if there’s a BCM issue, it may require reprogramming. Clear the codes and check if the message reappears. I recommend using your YouCanic Scanner to diagnose further, check for hidden faults, and potentially reprogram the BCM if needed. Let me know if you need more assistance