B1503 Exhaust heat management warning
What does B1503 mean on a Toyota?
B1503. Exhaust heat management warning. The combination meter detects a fault in the coolant temperature sensor line. This Toyota-enhanced code applies to Toyota, Lexus and Scion models that use this code.
Common causes of B1503
- Failed engine coolant temperature sensor
- Open or short in the coolant sensor line
- Loose or corroded sensor connector
- Damaged sensor harness
- Failed combination meter assembly
How to fix B1503
- Confirm the code and read temperature data
- Compare the coolant reading to a live scan value
- Inspect and reseat the coolant sensor connector
- Test the sensor line to the combination meter
- Replace the failed part only after tests fail