What it means
The engine coolant temperature 4 signal does not match plausibility checks against related signals. Sensor drift.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
Coolant temperature sensor 4 measures engine coolant temperature for the control module. This range/performance code means its reading may be electrically present but does not behave plausibly compared with related temperature signals or engine warm-up, suggesting drift or an installation issue.
Common causes
Most likely first.
- Sensor characteristic drifted
- Sensor mounting displaced from reference path
- Sensor element aged beyond calibration window
Symptoms
- Check engine light on
- Cooling fan runs constantly or not at all
- Cabin heater weak or excessively hot
- Possible long warm-up time or hard cold start
How to diagnose it
- Save freeze-frame data and, with the engine cold, compare sensor 4's reading with ambient temperature and the other coolant-temperature sensors.
- Watch sensor 4 live data during warm-up and look for a reading that changes smoothly and plausibly relative to the other temperature signals.
- Inspect sensor 4's connector, wiring, mounting, and coolant contact for damage, looseness, contamination, or displacement.
- Check the sensor 4 circuit for intermittent connection or resistance changes while gently moving the harness, following the manufacturer's procedure.
- If the circuit is sound but sensor 4 consistently disagrees with plausible reference readings, test the sensor against the manufacturer's specification and replace it if out of range.
Common fixes
- Secure sensor 4 in its correct mounting position and restore proper coolant contact.
- Clean and secure the sensor 4 connector or repair an intermittent harness connection.
- Repair damaged wiring affecting the sensor 4 signal.
- Replace coolant temperature sensor 4 if its response has drifted outside the manufacturer's specification.
Can I keep driving?
Monitor the temperature gauge and warning lights; stop if the engine overheats or coolant is lost. Until sensor 4 readings and fan operation are verified, avoid long drives or heavy loads because temperature control may respond incorrectly.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.