OBD-II code family
Control Module Internal Temperature Sensor Faults (4 codes)
4 related fault descriptions. Use each full code and the exact vehicle service information to identify its circuit, monitored condition, and required tests.
Codes in this family
This is the complete published member list for this guide. Each code retains its own page; shared diagnostic context does not mean that every member has the same test or repair.
What these codes mean
P0666 names an internal control-module temperature-sensor circuit result; P0667 adds range/performance, P0668 circuit low and P0669 circuit high. These sensor-monitor conditions are different from a code that explicitly reports control-module temperature too high. Keep the complete manufacturer description and reporting controller with the code.
Electrical low or high does not directly mean cold or hot. The sensor conversion and monitor determine the reported temperature. A stored result does not establish that the controller is overheating, that thermal protection has operated or that every other system is mechanically sound. Record actual propulsion, starting or shifting symptoms and investigate their relationship rather than assume a protective strategy explains them.
The archived 2009 Saturn Outlook FWD 3.6L P0667/P0668/P0669 procedure illustrates one implementation. Its TCM sensor is inside the control-solenoid/body/TCM assembly, is not serviced separately there and has no external sensor circuits to diagnose. That example does not establish the location or serviceability of every controller named in the generic descriptions. It also uses a separate transmission-fluid temperature input: the two readings are related observations, not automatically the same sensor.
The Outlook P0667 criteria consider temperature trends, comparison with fluid temperature and abrupt changes. Its P0668 low-voltage result uses an implausibly high reported temperature. Do not replace those application-specific checks with a universal overnight comparison, housing-touch test or external harness replacement. An internal-sensor reading must be interpreted using the installed controller’s own data and diagnostic requirements.
Save code status, event data, warnings and recent controller or transmission service history. Have the specified preliminary checks and temperature-monitor evaluation performed before choosing a sensor, complete assembly, programming or another repair. The code does not prove a bad ground, shorted driven device or software problem, and a generic title does not determine what can be serviced separately.
Do not open a sealed controller or reproduce a complaint with a road, warm-up or powered-connector experiment. Use the required isolation and controlled service procedure, then verify the demonstrated repair and any setup it requires. A cleared warning, normal warm engine or restart does not establish completed verification or driving safety. Follow actual temperature and propulsion warnings and obtain an itemized estimate for the confirmed job.
Identify the circuit on your vehicle
Match the full DTC, reporting module, and any failure-type suffix to the service information for your exact year, make, model, engine, and equipment. An identifier alone does not establish installed hardware count, location, connector pinout, or a universal measurement.
Where the manufacturer publishes its own meaning for this code, that is the one to work from — it describes the actual component on your vehicle, which the generic definition cannot. Keep the generic description for what it is good for: it tells you which subject area the standard assigned the code to, which is useful context when the two appear to disagree. If they do disagree, follow the manufacturer.