P0668: PCM / ECM / TCM Internal Temperature Sensor Circuit Low
MediumPowertrainEngine Electronics
What does P0668 mean?
P0668 is a diagnostic trouble code indicating "PCM / ECM / TCM Internal Temperature Sensor Circuit Low". The ECU is detecting a voltage reading that is below the expected range in the engine electronics circuit. This typically points to a wiring short, a faulty sensor, or a grounding issue.
Symptoms you may notice
- Check engine light (MIL) illuminated on dashboard
- Engine overheating
- Temperature gauge reading high
- Heater not working properly
- Intermittent warning lights
Estimated repair cost
Typical range in Australia (parts + labour)
$100 – $500 AUD
Common causes
- Damaged or corroded wiring harness
- Loose or disconnected electrical connector
- Failed engine electronics sensor or actuator
- Blown fuse in the related circuit
- Poor ground connection
What should you do?
This code sits in a powertrain control module. The engine or transmission can drop into limp mode or cut out, which is its own hazard in traffic or on a motorway. Get it diagnosed before your next trip rather than waiting for the next service.
Get a diagnosis for YOUR car
Code P0668 can mean different things depending on your vehicle. TorqueBot gives you a diagnosis specific to your make, model, and year.