Gauge Is Inaccurate

Disconnect coolant temperature sending unit. Connect one lead of Instrument Panel Tester (J-33431) to sending unit connector, and other lead to ground. With tester resistance dial adjusted to specified resistance, check temperature indicated on gauge. See the COOLANT TEMPERATURE SENDING UNIT RESISTANCE table.
If temperatures indicated on gauge are about equal to temperatures listed in table, replace sending unit. If indicated temperatures are not about equal to temperatures listed in table, check for high resistance in Dark Green wire between sending unit and instrument cluster. If wire is okay, replace instrument cluster.

COOLANT TEMPERATURE SENDING UNIT RESISTANCE