348 Grounding issue

I was trying to diagnose a problem with some of the sensors on the 348. When the car is running I measure 14.10 Volts at the battery which is normal. The interesting thing that I noticed was that there is a 0.18 Volt difference between the engine and the chassis. On my car, the battery ground connects to the negative terminal of the battery and the other end is attached to the engine block. This means that the car's computers, lights, instruments, and all electronics are running 0.18 Volts less then the sensors on the engine. Floating grounds typically lead to sensor reading issues. This issue is not obvious when the engine is not running , nor does there appear to be any measurable resistance between the chassis and engine block.
Most cars I have worked on usually have a grounding strap between the chassis and the engine. Does anyone know if later models have an engine to chassis grounding strap, or has anyone connected a grounding strap?
Thanks.