As Manny said, the problem is more likely to be a stuck closed or very lazy thermostat. Find someone with an IR gun and shoot the water outlet after driving long enough to normally warm up the engine. If the IR gun is about the same as the temp gage, and both are well below 80C, it's the thermostat. If the IR gun shows normal temp, 80C, but the gage reads low, the problem is the temp gage sensor, not the CIS-E/EZL temp sensor.

I am interested in the configuration of your CIS-E/EZL temperature sensor, but it's not clear from your description what you have. It is the most rearward sensor along "sensor row" between the cam cover and inlet manifold. Does it have a four-pole barrel connector? If not, can you provide a description of the connector or connectors, including number of poles.

The second from the rear sensor has a single pole connector, and it feeds the temp gage. If you remove the connector with the engine hot, the temp gage should react.

The third sensor from the rear is the cold start valve temp sensor. On early cars it actuates the cold start valve at 15C or below. Mine is blue. Later cars have a 60C or below cold start valve temp sensor, and that I believe it's a different color. What color is yours?

Pull each connector off and check the pins/receptables for damage or corrosion.

I've had an intermittent problem with speedometer needle wiggle in the 75-80 MPH range, which causes the cruise control to surge. It doesn't happen up to about 70. The speedometer cable on 190s is essentially sealed and cannot be lubricated, so the only option appears to be replacement. Mine was replaced on warranty, so it's fairly old, but doesn't have that many miles.

Last year I removed it from the transmission to check cable operation, and it spun smoothly with little friction.

Age and low temperatures can take a toll. When the weather gets warmer you speedometer wiggle situation may improve.