Trying to get some help on a 1997 3.8 Camaro that I have been working on for a while. The issue is that the PCM Temp and the Gauge in the cluster does NOT match. THE Gauge is reading about 50-60 degrees higher then the PCM temp. I have verified the PCM with my OBDII scanner. The PCM temp is running about 195-200 (195 degree thermostat) the Gauge is reading 250 + (most time pegs it out) and causes the "Check gauges" light to come on.
This car only has ONE sensor that feeds BOTH the ECM & Gauge

1. Wire Goes to the PCM(Yellow)
2. Wire is ground (Black)
3. Goes to the Gauge Cluster (green)

The things I have tired are

• Changed Temp sensor with New
• changed Cluster out with a Known good cluster
• Cut and changed the wiring Connector @ the sensor
• ran a new (Green) wire from the sensor to the last connector I could get to before the wires go under the dash . I can NOT get to the back of the cluster to run a completely new wire

So what am I missing ? Can someone give me some advice on what to try next ?

Thanks in advance