P0666

Control Module Internal Temperature Sensor A Circuit

Severity

⚠️ Medium

Can you drive?

Limited driving only, diagnose soon

Approx. repair cost

$33–889 (est.)

Symptoms

Check Engine light comes on
Engine runs fine in most modes
Possible interruptions at high ambient temperatures
Diagnostic code only without obvious symptoms (early stage)
Possible P0667 codes at the same time

Causes

Internal fault of the ECU temperature sensor (defect or degradation)
Previous ECU overheating, damaged sensor
Manufacturing defect in the electronic circuit of the ECU
Mechanical damage to the ECU board
Moisture trapped inside the ECU

How to Fix

Check the ECU location for overheating (insufficient ventilation, proximity to hot parts)
Check the correct installation and fastening of the ECU
Make sure there are no traces of moisture or corrosion on the ECU connectors.
ECU diagnostics on a specialized stand
If an internal malfunction is confirmed, repair or replace the ECU

Related codes

P0667 P0600 P0604 P0605 P0606