B1503 — OBD2 Diagnostic Trouble Code (Toyota)

B1503 Diagnostic Trouble Code (DTC) is stored when the Combination Meter Assembly (metre circuit plate) detects a malfunction in the Engine Coolant Temperature Sensor that is linked to the Combination Meter Assembly (metre circuit plate) through a direct connection.

When IG voltage is 9.5 V or more and the following condition is detected:

1.Water temperature sensor operation malfunction
2.Water temperature sensor circuit open or short
3.Engine coolant temperature is 120°C (248°F) or more