V8 M Model Stop-Sale Reportedly Issued For Transmission Wiring Harness Fault

If you’re looking to buy any of the V8-powered cars in the current M lineup in the immediate you future, you may have to put your aspirations on hold for just a bit. According to BMWBlog, BMW has had to stop selling all versions of the M5, M8, X5 M and X6 M with production that occurred between January and November of 2019. All of these cars employ similar versions of the S63B44T4 M V8 paired to a specialized variant of ZF’s eight-speed automatic transmission, and it is with the latter component where the fault lies.

Although no official statement has been made, it is said that the National Highway Traffic Safety Administration (NHTSA) has been notified and that a full recall is expected to take place next year, likely in February. The source for BMWBlog‘s claims are a handful of forum threads on BimmerPost.com, in which prospective buyers of the current M5 and M8 discuss being turned away from dealerships.

Getting into the specifics, it is the routing of the wiring harness for the ZF eight-speed automatic transmission that is causing problems. Apparently, the location and placement of the harness can result in damage to the wiring, which in turn causes a short circuit in the system. The ZF8 is an incredibly smart unit, and has a failsafe in that it will shift into neutral when a fault of this nature is detected, but a transmission unknowingly shifting into neutral without warning can certainly create a dangerous situation, especially on vehicles with the incredible performance of a modern BMW M car.

We don’t know if the wiring within the transmission harness is abrading against something and exposing live conduit, or routed too close to some kind of heat source, but whatever it may be, you can’t buy one of the affected models until it’s been sorted out. The production window encompasses nearly a full year of manufacturing, although it bears mentioning that not every model was being built during the entire period, as the X5 and X6 M were announced just a short time ago in October. A formal recall is expected to begin in February of next year, but once again, nothing has been officially confirmed.

The fault has reportedly affected at least one owner, who had to have the vehicle towed to the dealer via flatbed. Other accounts report that some new vehicles in dealer inventory have already had a fix performed, and are now back on sale. Additional details and firsthand information can be found here.—Alex Tock

[Photos courtesy BMW AG.]

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