What does "sensor reference voltage A" mean?

bloc

Veteran Member
Joined
Apr 25, 2006
Location
Austin, Tx
TDI
2013 Touareg TDI
tl;dr version: what does "sensor reference voltage A" mean and what sensors run off that reference?

Hello all,

So my G40 camshaft sensor/sensor reference voltage A issue just started to rear it's head again. Basically despite the intermittent G40 code, I replaced the G40, and the issue still comes up once in a while.

2010 CJAA/CR140 chassis

As of changing the sensor I still get a P0641 "sensor reference voltage A, open circuit" code once in a while. Usually accompanied by a G40 camshaft sensor implausible signal CEL, but not always. Noticeably more frequent when it is very cold outside, and the engine is cold. Has also happened once after a carwash in the summer, though I didn't wash under the hood. Also at the top of a very long fast hill on an interstate during the summer.

At this point I have to assume it is a wiring harness issue, though talking to a couple gurus they've not heard of this on a CJAA car so far.

So.. what sensors run off reference voltage A?

I'll start looking at the places that the BRM harnesses have issues but from reading around on here it seems the harnesses have been improved.

Thanks for any info.
 
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