What does the Jeep code P0688 mean?

A couple of months ago, my check engine light came on with code P0128. But since then, the light turned off by itself. My Jeep’s temperature stays right in the middle, it hasn’t overheated, and the air from the vents is very hot. I’ve never had any issues with the heat before or after this happened.

What do you think? Should I go ahead and replace the thermostat and coolant, or should I just leave it alone since everything seems to be working fine? I don’t want to cause new problems if the Jeep is running well right now.

Howdy,folks,
If you see this code, it is recommended that you have your Jeep inspected by a mechanic. They can utilize diagnostic instruments to determine the specific reason and offer appropriate repairs.

Jeep code P0688 corresponds to the ECM/PCM Power Relay Sense Circuit Open. When this diagnostic trouble code (DTC) is logged, it indicates an issue with the relay that provides power to the powertrain control module (PCM) from the battery. The relay could be faulty, or there might be a problem with its circuit. If you’re experiencing this issue, consider checking the PCM power relay and inspecting the wiring between the PCM and the relay.