If the Temperature gauge is going into the RED, and you have replaced the sensor - then this could be caused because the Instrument Pack Module (IPC) is not receiving the message from the Engine Control Module (ECM).
The temperature sensor sends its info to the ECM via hard wire.
The ECM then transmits this information on the communication wires (Corporate Area Network - CAN), to the IPC.
This leaves a number of potential causes:
- The hard wires from the Temp sensor to the ECM may have an intermittent break causing an open circuit - and therefore no info being sent to the ECM.
- The ECM has an intermittent internal fault.
- The ECM has a poor connection at the pins where the info is received back from the sensor or sent out on the CAN communication wires.
- There is an intermittent open circuit wiring concern between the ECM and the IPC on the CAN communication wires.
- There is a poor connection at the pins of the IPC for the CAN communications.
- The IPC has an internal fault.
To help determine this more clearly a fault code scan of the vehicle would be beneficial.
This would tell us:
- a code in the IPC is not receiving the info from the ECM
- or the ECM has a fault code stating it is unable to communicate with the IPC.
- or the ECM is not receiving the information from the temperature sensor.
If a code scan is not possible - then this would make the job slightly harder as continuity tests would need to be made between the ECM and the temperature sensor, the ECM and the IPC on the CAN wires.
CAN voltage checks, CAN resistance checks.
So for the moment the above information is a guide of the diagnostic route that could be taken.
I hope my advice has helped you understand the concern more clearly if not resolve it outright just yet.
Please 'Accept' my answer if this assists you to resolving your concern - this is the only way I will receive payment.
If the answer is not satisfactory - then please return for further assistance.
Please note - I may not be able to answer straight away myself - as I work full time during a normal working week. - However there will be other experts who will assist you further if this is the case.