P0669

Symptoms

• The Check Engine light comes on
• Switching to emergency engine operation mode
• Reduced power and throttle response
• Unstable operation of the vehicle's electronic systems
• Possible overheating of the ECU

Causes

• Short circuit of the signal wire to the power line (+12 V)
• Temperature sensor ground circuit open
• ECU internal temperature sensor malfunction
• Oxidation or contamination of the ECU connector
• Internal ECU fault

How to Fix

1. Read error codes and record data freeze frame with OBD-II scanner
2. Inspect the ECU connectors and wiring for damage, oxidation, and traces of moisture.
3. Measure temperature sensor A signal circuit voltage (normal: 0.5 - 4.5 V)
4. Check the sensor ground circuit with a multimeter for an open circuit.
5. Check signal wire for short circuit to +12 V
6. If the external circuit is in good condition - diagnostics of the ECU with possible replacement

Related codes

Error P0669 by Vehicle Brand