Is this a Dzero? This literally just happened to my Dzero also. I connected it to the AXS app and it still shows torque readings but never watts. I reached out to SRAM support and they didn't know what was up and that I would need to RMA it which could be a hassle since I bought it new but from a private party. I also saw someone else on facebook marketplace selling a unit with the exact same problems as mine. There actually seems to be a wave of this going on.

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Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
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+1 for this problem on my DZero.
Would've cost way more to remove and send off (would've had to source new 165mm crank arms/spider which are like gold dust). Instead, took the L and have left on bike and just got a set of Assiomas.

Interesting. How recently did it happen? It just seems so odd that it had worked flawlessly for like two years and then all of a sudden stopped displaying anything. Pushes me pretty hard into the power2max camp instead of Quarq.

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Benjamin Deal - Professional - Instagram - TriRig - Lodi Cyclery
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There is something wrong with the DZero spiders. Or at least the standard 5-bolt DZero spiders. I’ve had over a dozen Quarqs from nearly the beginning and the only one that has failed is a Dzero. I’m on my fourth unit. Every failure followed a chain drop. Only one of the 3 failures (the first one) came from a heavy or even violent drop. It has something to do with the chain contacting the back of the spider. I suppose any contact on the backside could do it. Mine always showed huge zero offset numbers after failing.

Haven’t had the issue with DFour units though that may be because the Shimano rings don’t lead to many drops. Haven’t seen an issue with the AXS Quarqs yet.

They do provide a fairly quick turnaround swap time. No need to send the crankarms. Spider and ring removal isn’t that difficult. It sure how they respond to private sales SRAM/Quarq can be finicky about warranty compared to what Quarq used to provide.

Not that it'd necessarily help with fixing the issue, but I wonder if however it determines cadence is broken if you're still getting torque readings, since power is torque * cadence. Looks like the DZero meters use an accelerometer for cadence so it wouldn't be something like the magnet falling off (which it sounds like could be an issue for the older versions).

99% it's one of two things above. Chain drop kills the spider, normally leading to calibration values on the -32000 range, or the accelerometer as well described above

But conversely, support been good for me over the years, both in us and in overseas via local distributor

I had issues with 2 DZero (5 bolt 110BCD) units between the end of 2018 and the first half of 2019. Original unit worked for a few weeks then had crazy spikes and then would drop in and out. Customer support was quick after the holidays and the second unit worked fine for a few months then started to do the same. This was all on my 1x gravel bike, which I’ve never dropped a chain on, it was just out of the blue. I received my second replacement (3rd spider overall) and sold it. I’ve used a dozen P2M units without fail so went back to that and has been rock solid since.
I’ve seen posts on various forums with similar stories to mine and tons of people that never had an issue so not sure what to make of it.

Happened like 7 or 8 months ago and happened out of the blue. No chain drops etc and PM didn't event start spiking, just straight up stopped. Has been w/o battery in ever since. Tested again today and still broken. Rip.
Assioma’s were most financially viable option but a real shame as I’d love to be using Speedplay pedals.

Zero power. Train more. Sorry, couldn't resist.

I have a sworks venge so although branded specialised I think it is a quaq? Not sure exactly which model which makes it harder to problem solve. I guess I can take it back to the dealer, they just had it for 2 months getting my second warranty replacement on the etap levers which have been faulty. They will have had enough of this bike !