P0189
UniversalFuel Temperature Sensor B Circuit Intermittent
Medium SeverityThis code indicates that the vehicle's engine control module (ECM) is detecting an intermittent signal from the Fuel Temperature Sensor B. An intermittent signal means the sensor's readings are sporadically changing or dropping out, which can lead to inaccurate fuel mixture calculations and affect engine performance or fuel efficiency.
⚠️ Before You Begin (Safety First)
Always ensure the vehicle is parked on a level surface with the parking brake engaged before performing any work. If dealing with the fuel system, ensure proper ventilation and have a fire extinguisher nearby. Always disconnect the battery before working on electrical components to prevent accidental shorts or injury.
Common Symptoms
- Check Engine Light illumination
- Reduced fuel efficiency
- Rough idle or stalling
- Poor engine performance or hesitation during acceleration
- Difficulty starting the engine
Common Causes
- Faulty or failing Fuel Temperature Sensor B
- Loose, corroded, or damaged wiring or connectors in the sensor's circuit
- Intermittent open or short in the sensor wiring
- Contaminated fuel affecting sensor readings
- Less commonly, a faulty Powertrain Control Module (PCM)
Frequently reported on: Ford F-150 (2005-2014), Chevrolet Silverado 1500 (2007-2013), Dodge Ram 1500 (2003-2009), Honda Civic (2006-2011), Toyota Camry (2007-2011)
Diagnostic Steps
- Connect an OBD-II scanner to verify the P0189 code and check for any other related codes. Clear the code and test drive to see if it returns.
- Visually inspect the Fuel Temperature Sensor B and its wiring harness for any signs of damage, fraying, corrosion, or loose connections.
- Disconnect the sensor and inspect the terminals for corrosion or bending. Clean or repair as necessary.
- Using a multimeter, test the resistance of the fuel temperature sensor (if specifications are available) at various temperatures, if possible. An intermittent reading indicates a faulty sensor.
- If the sensor tests good, check the continuity of the wiring from the sensor to the PCM. Look for any intermittent open circuits or shorts.
- Replace the Fuel Temperature Sensor B if it is determined to be faulty.
- After replacement, clear the code and perform a test drive to confirm the repair.
👨🔧 When to Call a Professional
If after inspecting wiring and connections, the issue persists, or if specialized diagnostic equipment is needed to accurately test the sensor's voltage and resistance, it's best to consult a professional mechanic. Fuel system diagnosis can be complex and requires precision.
Commonly Asked Questions
What does an "intermittent circuit" mean for P0189?
It means the signal from the fuel temperature sensor to the engine computer is not consistently stable; it might drop out or fluctuate unexpectedly.
Can I ignore the P0189 code?
While it may not cause immediate severe issues, ignoring it can lead to reduced fuel economy, poor engine performance, and potentially damage other components over time due to incorrect fuel mixtures.
Where is Fuel Temperature Sensor B located?
The location can vary significantly by vehicle. It might be in the fuel tank, along the fuel line, or within the fuel rail. Consult your vehicle's service manual for the exact location.
What is the most common fix for P0189?
The most common fix is replacing the faulty fuel temperature sensor B, often after verifying wiring and connections are intact.
Does P0189 affect emissions?
Yes, an intermittent fuel temperature reading can cause the engine control unit to miscalculate fuel delivery, potentially leading to increased emissions and a failed emissions test.