"MultiPlus 12/3000/120-16 (Product ID 1909) - firmware v159, GX Error #48, Not updatable (1342)

Picked up a second-hand MultiPlus 12/3000/120-50 a while back for the static and ran into something similar — bought it off eBay, seemed like a decent deal, then plugged it into the Cerbo GX and got Error #48 staring back at me. Not the welcome I was hoping for.

Turned out the firmware was well behind and the GX simply wouldn't talk to it properly. The "not updatable" flag through VictronConnect was the frustrating bit — it's almost like the unit gets stuck in a limbo state where the normal update path just won't work.

What sorted it for me was going direct via the VE.Bus cable and updating through VEFlash on a laptop rather than trying to push the update over VE.Direct or through the GX device. Bit old-school but it got the job done. Worth making sure you've got the right MK3-USB interface as well — some of the cheaper clones people sell alongside these units can cause their own headaches.

A few things I'd check if you're in the same boat:

• Product ID — some older units have quirks about which firmware branch they'll accept
• VEFlash rather than VictronConnect for stubborn cases
• Victron's community forum has firmware files going back years if you need a specific version

Anyone else bought secondhand Victron kit and hit similar firmware walls? Feels like it's becoming more common as older installs get broken up and bits end up on the used market. Would be good to build up a bit of a reference here for what works.

Hey @BigAl, that Error #48 is a right pain isn't it! Just to add something that might not have been mentioned yet — that particular firmware version (v159) on older product IDs sometimes needs a direct VE.Bus connection via a MK3-USB interface rather than going through the GX device to do the update. Victron's VictronConnect app on a laptop with the MK3-USB dongle bypasses the GX entirely and can sometimes crack it when the over-the-air route fails. Worth a shot if you haven't tried it already. The MK3-USB adapters are about £30-40 new but you can sometimes borrow one from a local Victron dealer — a few will do a bench update for a small fee too. Might save you a headache!

@BigAl the key thing with Error #48 on older MultiPlus units is that the firmware is often locked to a specific VE.Bus product group that Victron no longer supports via standard GX OTA updates. The "Not updatable (1342)" code is the Cerbo telling you the unit needs direct firmware flashing via a MK3-USB interface and VE.Bus System Configurator on a Windows machine — not through VictronConnect or the GX device itself.

Grab the MK3-USB (about £35 from Bimble Solar or Victron dealers), download VE.Configure Tools from Victron's website, and you can manually push the correct firmware directly to the unit over the VE.Bus port.

Done exactly this on my boat's MultiPlus. Once flashed to a supported firmware version it'll integrate with the Cerbo properly and the error clears.

Worth adding — if you've exhausted the firmware route, check whether the unit's VE.Bus address is conflicting with anything else on the network. Had this exact mess on my motorhome build last year, Cerbo just threw a wobbly and wouldn't play nice until I physically isolated the MultiPlus and ran MK3-USB diagnostics directly from VictronConnect on a laptop.

Sometimes the GX device is the problem, not the inverter.

Also @BigAl — eBay MultiPlus units are a lottery. Some have been flashed with dodgy regional firmware or had their product IDs mucked about with by whoever owned them before. Victron dealer can run a proper unit check if you're stuck. Might cost a bit but beats chasing your tail for weeks like I did.

@BigAl had exactly this circus with a secondhand MultiPlus on the narrowboat — the dirty secret nobody tells you is that Victron tie firmware update eligibility to the product ID and original dealer chain, so some grey-market units are effectively bricked at that version forever, full stop.

Before you throw it at the wall, grab MK3-USB interface and try forcing the update through VEConfigure directly rather than going via the Cerbo — occasionally bypasses the GX's error logic when the units are being dramatic.

If that fails, ring Victron UK (not a reseller, the actual distributor) with the serial number — they can sometimes unlock it on their end, though whether they'll bother for an eBay special is another matter entirely.