I own a 1991 300zx 2+2 NA with only 91000. While driving the speedometer dropped to zero and the power steering stopped working. I pulled a Marty Mcfly and tapped on the top on the steering column and everything started working again. This vehicle is mainly stored and just occasionally driven not many miles on some weekends. I was able to repeat this same process on my cruises when it happened again, however on one drive I was unable to get the vehicle to regain the power steering and speedometer to read. I am no expert, so any help would be greatly appreciated.

Sean

The steering is active, so it’s uses input from the speed sensor. If the speedometer fails to work it will stop the power assist steering. You car being an import will likely have a speed converter behind the dash, loose connection here on this circuit will be the cause. You tapping probably remade the connection. Also the speed sensor on the gearbox can pop out the end, be loose, simply slowly down and speeding back up it can kick back to life.

On 17/05/2026 at 09:23, Stephen said:

The steering is active, so it’s uses input from the speed sensor. If the speedometer fails to work it will stop the power assist steering. You car being an import will likely have a speed converter behind the dash, loose connection here on this circuit will be the cause. You tapping probably remade the connection. Also the speed sensor on the gearbox can pop out the end, be loose, simply slowly down and speeding back up it can kick back to life.

I thought speed sensor too....

Common failure - the plastic cap comes loose and pops out. Simple fix is is to coat the cap in epoxy resin and push it back in - long term fix is a new speed sensor.

Easy to replace, albeit a bit fiddly, but it can be hard to get access to the cable connector block, whilst the gearbox is in situ!