Gauges won't reset to 0.

2000 New Beetle with 211,000 miles. I've tracked down 13 CELs for a friend and she is left with 1 problem which I can't find any information on.

The last CEL is an implausible engine speed problem and in her words "really bad gas mileage" (no she doesn't put gas in the car).

I couldn't seem to track it down until I drove the car myself and found out the both the tachometer and gas gauge intermittently don't reset themselves to 0 when you turn the car off. When the tach doesn't reset, it throws the implausible CEL on the next start cycle. When the gas gauge doesn't reset correctly, the "really bad gas mileage" happens.

If I turn the car ignition on and off without starting the engine a few times the gauges eventually will reset a little each on/off cycle until they reach zero and all is fine for a while, then it happens again. No real pattern to when, just random.

Any ideas?

Sounds like a bad cluster, but the CEL is strange. what is the "implausible CEL" exactly? is the light just coming on or is the ECM actually storing a code?

I agree sounds like bad cluster is a possibility. probably not the issue but here's a long shot: make sure the connector plug for the coolant level sensor is dry to rule out coolant migration, too

If the code actually reads "Engine Speed Senosr: Implausible Signal" then that usually points to the Engine RPM sensor which bolts into the side of the block near the flywheel.

Does the code also read "Intermittent" after implausible signal?

It would have nothing to do with the cluster not resetting, so you could still have a combo of problems (bad sensor, bad cluster, coolant migration, etc)

I just had a deeply sinking sensation in my stomach. I had a 99.5 gasser Jetta that ended up having a defective engine harness. it cost me 2 ECUs, the harness of course, a cat, and a drive shaft. I would get odd codes that no amount of parts would fix. One day it went berserk, I poked the throttle a few times to coax movement (in rush hour traffic mind you) and then it found itself long enough to slam full power down, shattering the outer right CV. While this doesn't sound like anything to do with your problem, make sure you ring out every engine circuit that is related to the issues you're having. Any shorts or faults could lead to... extraneous adverse consequences.