DSC/brake lights on, Engine Failsafe light on

[Oldmactech]

Getting the DSC / Engine failsafe dashboard light. About every other trip. ( only103k mi on 03-3.0) doesn’t get driven long or hard much.

E46 I had did the same, battery was weak. Replaced battery, fixed it.

This battery was 6 yrs old so I swapped a new one in. Not as frequent but still doing it.

After it sits, restart clears it temporarily.

Possible bad replacement battery? ( NAPA battery)
Anything else to look at?

Thanks.


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[andrewwynn]

Three symptoms describe failing Alternator or voltage regulator.

A better battery acts as a voltage stabilizer which is why you will see improvement from a new battery.

A voltage meter with a high/low function is the best way to confirm but you can usually tell from watching the voltage on the hidden OBC menu.

[Oldmactech]

Having trouble activating onboard OBC, is there an E53 specific source for steps. I get an odd message- 581 SIA, won’t let me cycle past that.


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[Oldmactech]

Actually says “reset sia: 575 1


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[Oldmactech]

Got into the OBC. Charging fluctuates between 13.5v and 13.7v. I’m guessing it should stay on a higher number and not drop. I just started getting and ICV control mechanical failure CEL, might be related?


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[Fifty150hs]

Originally Posted by Oldmactech

Got into the OBC. Charging fluctuates between 13.5v and 13.7v. I’m guessing it should stay on a higher number and not drop. I just started getting and ICV control mechanical failure CEL, might be related?


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13.5 to 13.7 is normal charging voltage. Do you have a scanner? I think the Foxwell can monitor this voltage real time and graph it as well which would allow you to see if the voltage momentarily drops too low. A failing alternator can do that. It's brief, but enough to throw codes.

[andrewwynn]

What you are looking for is a dip in voltage when you start coasting to a stop light etc.

I've had 3-4 e53 Alternator fails and every time I could see the voltage dip to say 12.5 right after I lift off throttle from say 35 mph.

If you had an oil leak issue that wetted the alternator the odds are nearly 100%.

That said, I've refurbished a couple valeo models and it's not difficult for $20.

Graph the voltage or if you have a good DMM, record min. /max. The dip or peak could be milliseconds, you won't see but the computer will.

[Oldmactech]

Thanks. I suspect the alternator took in some water when the filler tank busted a couple of years ago.
Drove a few miles yesterday with my scanner connected but the graph was flat. (No dash board warning lights)
Will continue that until the lights kick on.


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[Oldmactech]

Update/no update

Now driven 15-20 miles with my scanner connected to monitor voltage. Graph has flatlined at 12.7 except on start which would be normal. No idiot lights thus far.

I must say that I reset the adaptations through my scanner, maybe that contributed?

[andrewwynn]

12.7 might be on the very low side of "within spec" but I've never tested a car that low. I would be replacing a VR that output 12.7. Normal is almost a volt higher.