B1421 - FAULT CODE - OBD2

POST UPDATED IN January, 2023

B1421 Code failures by brands

B1421 LEXUS, TOYOTA, SCION: SOLAR SENSOR CIRCUIT PASSENGER SIDE

Description of DTC code B1421

The Sun Sensor is a device installed on the top of the instrument panel. Its function is to detect sunlight to control the AUTO mode of the Air Conditioning system. The output voltage of this sensor changes according to the amount of sunlight. When the light increases, the output voltage increases accordingly. If the light decreases, the output voltage decreases accordingly. On the other hand, the air conditioning amplifier detects all these voltage changes.

The DTC B1421 OBDII code is set because a fault was detected in the passenger side Solar Sensor circuit.

Symptoms of fault code B1421

Causes of OBD2 B1421

Reasons for setting diagnostic code B1421 OBD2:

  • Solar Sensor circuit wires may be in poor condition.
  • The Solar Sensor circuit may have poor connections, resulting in a short or open circuit.
  • The Solar Sensor may be faulty.
  • The air conditioning amplifier may be defective.

Possible solutions of the DTC code B1421

To solve the B1421 OBDII fault code, try to follow these steps:

  • First, consult the Technical Service Bulletins.
  • Check the Solar Sensor circuit wiring for damage. If you discover deficiencies caused by wear or corrosion, make the appropriate repairs.
  • Measure the Solar Sensor circuit voltages to verify that the circuit is not open or shorted. If the actual voltages differ from those specified, make corrections.
  • Check the Solar Sensor and air conditioner amplifier for damage. To check their integrity, follow the manufacturer's recommendations. If damage is found in any of these components, make the right adjustments.

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