Lexus LX Battery Sensor Issue

My 2009 Lexus LX diesel is giving me fits. It only has 47289 km on the clock! Lately, the battery seems weak when starting, especially in the mornings. I've also noticed the lights flicker sometimes, even at idle. I had a look with an OBD reader and it is complaining about the battery sensor. Could this be the culprit, or am I missing something obvious?

4 comment(s)

Flickering lights and hard starts often point to voltage issues. The error code points at the battery sensor. What voltage readings are you getting across the battery terminals when the engine is off, and while it's running? This might give us clues.

I checked the voltage as you suggested. When off, it reads 12.1V, which seems a bit low. While running, it jumps to 13.5V, but fluctuates a bit. Is that fluctuation normal, or does it further indicate a faulty sensor?

12.1V is indeed low for a resting battery and fluctuating voltage while running suggests the sensor is not properly regulating the alternator's output. Seeing that the sensor error came up in the diagnostic, I'd wager replacing it is the correct path forward. It's a fairly straightforward job, but if you're not comfortable with electrics, I'd recommend taking it to a workshop.

I took your advice and had the battery sensor replaced. The workshop confirmed it was defective. The total cost was 315€, but the starting issue and flickering lights are gone now. Thanks again for pointing me in the right direction; you saved me a lot of time diagnosing!

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