Fuel Temperature Sensor B Circuit Intermittent
The P0189 code indicates that the Engine Control Module (ECM) has detected an intermittent signal from the fuel temperature sensor B circuit. This sensor monitors the temperature of the fuel in the fuel rail or tank, and the ECM uses this data to adjust fuel delivery and timing. An intermittent fault means the signal is erratic or drops out occasionally, often due to wiring issues, poor connections, or a failing sensor. This can lead to incorrect fuel mixture, reduced fuel economy, and potential drivability issues.
1. Most Common Causes
- Faulty or intermittently failing fuel temperature sensor 'B'
- Corroded, oxidized, or loose electrical connections at the sensor connector
- Intermittent short to ground or voltage in the sensor circuit wiring
- Wiring harness damaged by chafing, heat, or vibration causing sporadic faults
- Bent, pushed-back, or low-tension pins in the connector
- Excessive circuit resistance due to poor splices or grounds
2. Symptoms You Will Notice
- Check Engine Light illuminated
- Poor fuel economy
- Rough idle or hesitation during acceleration
- Hard starting, especially when hot or cold
3. Step-by-Step Diagnosis
Step 1: Use an OBD2 scanner to confirm the code and check for other related codes.
Step 2: Visually inspect the fuel temperature sensor B and its wiring for damage, corrosion, or loose connections.
Step 3: Test the sensor's resistance and voltage with a multimeter and compare to manufacturer specifications.
Step 4: Check for intermittent issues by wiggling the wiring harness while monitoring the sensor signal with a scan tool.
4. Frequently Asked Questions
Is it safe to drive with this code?▼
It is generally safe for short trips, but the intermittent nature can cause drivability issues and reduced fuel economy. It's best to diagnose and repair promptly to avoid potential damage to other components.
How much does it cost to fix?▼
The cost typically ranges from $50 to $150, including parts and labor. The sensor itself is usually inexpensive, but labor costs vary depending on location and vehicle accessibility.
5. Commonly Affected Makes
This is a generic OBD2 code, potentially applicable to any manufacturer using this diagnostic standard.