The B1223 OBD2 fault code relates to the Fuel Temperature Sensor #1 circuit. This sensor monitors fuel temperature and sends data to the engine control module (ECM) or body control module (BCM). When the circuit open circuit, the module cannot read accurate temperature values, which may affect fuel delivery calculations and emissions control.

At AIscanAuto, we help drivers quickly identify OBD2 trouble codes, understand their root causes, and find the right fix — without the guesswork.

Symptoms

• Check Engine Light (CEL) illuminated on the dashboard
• Inaccurate or erratic fuel temperature readings
• Possible fuel delivery issues in extreme temperatures
• ECM may adjust fuel mixture incorrectly
• Hard starting or poor performance in cold/hot weather

Common Causes

• Faulty temperature sensor — internal damage or contamination
• Wiring issues — broken, corroded, or chafed wires in the sensor circuit
• Connector problems — loose, oxidized, or moisture-damaged pins
• an open circuit is detected — indicates a break in the circuit path, resulting in no signal transmission
• Open circuit — complete wire break interrupting signal path
• Module input failure — rare, but the ECM/BCM input stage may be defective

Step-by-Step Diagnosis

1. Scan with OBD2 tool — Confirm B1223 is active. Check for additional DTCs.
2. Visual inspection — Examine the Fuel Temperature Sensor #1 wiring and connector for corrosion or damage.
3. Check voltage and ground — Use a multimeter to verify proper reference voltage.
4. Test sensor resistance — Compare readings to factory specs. A stuck or erratic signal confirms failure.
5. Check for shorts/opens — Perform continuity tests on the wiring between the sensor and control module.

Repair & Solutions

• If the sensor is defective, replace the Fuel Temperature Sensor #1 with an OEM or quality aftermarket part.
• Repair any damaged wiring or connectors using proper methods.
• Clear the DTC with an OBD2 scanner and test drive to verify the code does not return.
• If the code persists after sensor replacement, inspect the ECM/BCM connector.

Related Codes

• B1220 — Fuel Tank Pressure Sensor Circuit Open
• B1221 — See Manufacturer
• B1222 — Fuel Temperature Sensor #1 Circuit Failure

External References

• OBD2Pros — Complete DTC Reference
• TuningBot — OBD2 Codes Explained

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About This Guide

This diagnostic article is an original guide created by AIscanAuto for educational and troubleshooting purposes. The technical information about OBD2 DTC codes is based on publicly available automotive diagnostic standards and industry best practices. External links provided in the "External References" section are for additional reading and context only — they do not imply endorsement or ownership of third-party content. All repair procedures should be performed by qualified technicians.