P0189 is a generic OBD-II powertrain fault code that means Fuel Temperature Sensor B Circuit Intermittent. The ECM/PCM has detected an unstable, intermittent, or implausible signal from the fuel temperature sensor B circuit.
The problem may be caused by the sensor itself, an intermittent wiring fault, a loose or corroded connector, poor terminal contact, an open or shorted circuit, or, less commonly, a control-module problem. The exact sensor configuration and diagnostic procedure vary by vehicle and engine.
Fault Code Description
P0189 = Fuel Temperature Sensor B Circuit Intermittent.
Code type: Generic OBD-II Powertrain Code.
Likely fault location: Fuel temperature sensor B, sensor connector, wiring harness, signal circuit, power/ground circuit, or ECM/PCM input circuit.
The word Intermittent means the ECM/PCM is not seeing a stable sensor signal. The signal may temporarily become normal and then drop out, spike, become implausible, or disappear altogether.
What Does P0189 Mean?
When P0189 is stored, the ECM/PCM has detected an intermittent or unstable signal from fuel temperature sensor B.
Because fuel temperature information can be used as part of fuel-system calculations, an unstable sensor signal may cause incorrect fuel-temperature data and, depending on the vehicle, affect fuel-control strategy.
P0189 does not automatically mean that the fuel temperature itself is changing rapidly. In many cases, the actual problem is electrical: a loose terminal, damaged wire, poor connector contact, or a sensor that intermittently loses its correct output.
Fuel Temperature Sensor B
Fuel temperature sensor B provides the ECM/PCM with information about fuel temperature. The exact sensor location and design depend on the vehicle.
On some applications, the sensor may be integrated into another fuel-system component rather than being installed as a separate standalone sensor.
The letter B identifies the circuit or sensor designation used by the manufacturer. It does not necessarily mean that every vehicle has two externally visible fuel-temperature sensors.
Symptoms of P0189
- Check Engine Light.
- Fuel temperature reading that suddenly changes or becomes implausible.
- Intermittent engine hesitation.
- Rough or unstable engine operation.
- Reduced fuel economy.
- Hard starting in some applications.
- Incorrect fuel-control calculations.
- Additional fuel-system or temperature-sensor codes.
- Symptoms that appear and disappear depending on vibration, temperature, or harness movement.
Common Causes of P0189
- Failing fuel temperature sensor B.
- Loose electrical connector.
- Corroded sensor terminals.
- Damaged or partially broken wiring.
- Intermittent open circuit.
- Intermittent short to ground.
- Intermittent short to voltage.
- Poor terminal tension inside the connector.
- Water or contamination inside the connector.
- Harness rubbing against the engine or chassis.
- Heat-damaged wiring.
- Unstable sensor power, reference, or ground.
- Rarely, an ECM/PCM fault.
How to Fix P0189
1. Scan the Vehicle
Use a suitable scan tool to confirm P0189 and check for additional stored, pending, or history codes. Record the freeze-frame data before clearing the code.
Pay particular attention to whether the fault occurs together with other fuel-temperature, fuel-pressure, or electrical codes.
2. Check Fuel Temperature Live Data
Monitor the fuel temperature parameter with the scan tool. Watch for sudden jumps, dropouts, unrealistic values, or a reading that freezes while other engine parameters change.
An intermittent sensor circuit may appear normal while the vehicle is stationary, which is why observing live data during the fault can be especially useful.
3. Inspect the Sensor Connector
Inspect the fuel temperature sensor B connector for corrosion, loose terminals, damaged locks, water intrusion, contamination, or poor terminal tension.
A connector can look visually normal while still having a weak electrical connection.
4. Perform a Wiggle Test
With the scan tool monitoring the fuel temperature parameter, carefully move the sensor harness and connector while observing the data.
If the temperature reading suddenly changes when the harness is moved, the wiring or connector may have an intermittent fault.
5. Check the Wiring
Inspect the complete wiring path between the sensor and ECM/PCM. Look for broken conductors, damaged insulation, rubbing, heat damage, corrosion, and areas where the harness can move or contact another component.
6. Test Power, Ground and Signal
Use the vehicle-specific wiring diagram to identify the sensor power, reference, ground, and signal circuits.
Check for voltage drop, intermittent opens, shorts, and unstable connections. The exact test method depends on the sensor design and manufacturer specifications.
7. Test the Sensor
If the wiring and connector are verified, test fuel temperature sensor B according to the manufacturer's specifications.
Depending on the system, testing may involve resistance, voltage, scan-tool data, or another specified procedure.
8. Check the ECM/PCM
If the sensor and complete circuit test correctly but the intermittent fault remains, inspect the ECM/PCM input circuit and check for applicable manufacturer technical service information.
The ECM/PCM should be considered only after the sensor, wiring, connector, power, ground, and signal have been properly tested.
P0189 Diagnostic Signal Flow
↓
Fuel Temperature Sensor B
↓
Sensor Signal Circuit
↓
ECM / PCM
↓
Fuel Temperature Calculation
↓
Fuel Control Strategy
P0189 OBD Live Data
OBD live data is particularly useful for an intermittent code such as P0189. Monitor the fuel temperature parameter while the engine is running and look for sudden changes that do not match the actual operating conditions.
If the value suddenly jumps or drops when the wiring harness is moved, when the engine vibrates, or when the vehicle reaches a particular temperature, the problem may be in the sensor circuit rather than the fuel itself.
The expected fuel-temperature value depends on ambient temperature, fuel temperature, engine operating conditions, fuel-system design, and manufacturer specifications.
P0189 Signal and Oscilloscope Check
For difficult intermittent faults, an oscilloscope can be useful for monitoring the sensor signal while the harness, connector, engine, or vehicle is subjected to the conditions that reproduce the fault.
A stable sensor signal should remain within the manufacturer's expected electrical range. An intermittent open, loose terminal, or damaged wire may appear as sudden dropouts, spikes, interruptions, or signal instability.
The exact waveform depends on the sensor design, so the manufacturer's waveform and electrical specifications should be used as the reference rather than a generic waveform.
P0189 Wiring Check
The wiring configuration varies between manufacturers and engines. Do not assume that the sensor uses the same pinout, voltage, or circuit arrangement on every vehicle.
Always verify the connector pinout and wiring diagram for the exact vehicle and engine before applying voltage, ground, or test equipment to the circuit.
P0189 Duramax
On applicable Duramax applications, P0189 indicates an intermittent condition involving the fuel temperature sensor B circuit.
On a Duramax, intermittent faults deserve particular attention because vibration, engine temperature, harness movement, and connector condition can affect an electrical connection.
Diagnosis should begin with scan-tool data and inspection of the sensor connector and harness. Perform a wiggle test and circuit checks before replacing the sensor.
The exact sensor location and circuit identification can vary by Duramax generation, so the correct service information for the specific engine should be used.
P0189 Chevrolet
On applicable Chevrolet vehicles, P0189 indicates that the ECM/PCM has detected an intermittent signal from fuel temperature sensor B.
Check the sensor, connector, terminal tension, wiring, power, ground, and signal circuit. If the fault appears only under vibration or certain operating conditions, concentrate on intermittent wiring and connector problems.
P0189 Chevrolet Duramax
On Chevrolet trucks equipped with an applicable Duramax diesel engine, P0189 should be diagnosed using the exact engine and model-year service information.
Do not assume that the sensor location or circuit is identical across different Duramax generations. Use the wiring diagram and scan-tool data to identify the correct fuel temperature sensor B circuit.
P0189 L5P Duramax
On an applicable 6.6L L5P Duramax, P0189 should be treated as an intermittent fuel temperature sensor B circuit fault rather than automatically assuming that the fuel itself is the problem.
For L5P diagnosis, verify the exact sensor and circuit using the vehicle-specific GM service information. Then monitor fuel-temperature live data and inspect the related connector and harness for intermittent electrical contact.
Because the L5P has a complex diesel fuel system and multiple temperature and pressure inputs, it is important to identify the correct sensor circuit before testing or replacing a component.
Is P0189 Serious?
P0189 should not be ignored. The severity depends on whether the intermittent signal is affecting fuel-control calculations or causing other drivability problems.
If the vehicle has severe hesitation, stalling, hard starting, major power loss, or multiple fuel-system faults, it should be diagnosed before continued driving.
Can I Drive With P0189?
Limited driving may be possible if the engine is running normally and the Check Engine Light is steady. However, an intermittent fuel-temperature sensor fault should be diagnosed as soon as practical.
If the vehicle develops severe drivability problems, reduced power, stalling, or difficult starting, continued driving should be avoided until the cause is identified.
P0189 Repair Cost
The repair cost depends on whether the fault is caused by the sensor, wiring, connector, or another component.
- Electrical diagnosis: approximately $50–$150+.
- Connector or terminal repair: approximately $50–$200+.
- Wiring repair: approximately $50–$300+.
- Fuel temperature sensor: approximately $80–$350+ depending on the vehicle.
- ECM/PCM diagnosis or repair: can cost considerably more.
These are general estimates only. Actual repair cost depends on the vehicle, engine, parts prices, labor rate, sensor location, and the actual cause of the intermittent fault.
Common Repair Mistakes
Replacing the Sensor Immediately
An intermittent code does not automatically mean that the sensor is defective. Wiring, connectors, terminal tension, and harness movement should be checked first.
Ignoring the Connector
A loose or corroded terminal can create an intermittent signal while the sensor itself remains functional.
Checking the Circuit Only When It Is Working
Intermittent faults can disappear during testing. Monitoring live data while reproducing the fault can be more useful than performing a single static voltage measurement.
Using the Wrong Pinout
Sensor circuits differ between manufacturers, engines, and model years. Always verify the exact wiring diagram before testing.
Related Codes
- P0180 – Fuel Temperature Sensor A Circuit Malfunction
- P0181 – Fuel Temperature Sensor A Circuit Range/Performance
- P0182 – Fuel Temperature Sensor A Circuit Low Input
- P0183 – Fuel Temperature Sensor A Circuit High Input
- P0184 – Fuel Temperature Sensor A Circuit Intermittent
- P0185 – Fuel Temperature Sensor B Circuit Malfunction
- P0186 – Fuel Temperature Sensor B Circuit Range/Performance
- P0187 – Fuel Temperature Sensor B Circuit Low Input
- P0188 – Fuel Temperature Sensor B Circuit High Input
- P0190 – Fuel Rail Pressure Sensor Circuit
FAQ About P0189
What does P0189 mean?
P0189 means Fuel Temperature Sensor B Circuit Intermittent. The ECM/PCM has detected an unstable or intermittent signal from the fuel temperature sensor B circuit.
How do I fix P0189?
Start by checking the codes and freeze-frame data, then monitor fuel-temperature live data. Inspect the sensor connector and wiring, perform a wiggle test, verify the circuit, and test the sensor according to the manufacturer's specifications.
What is the most common cause of P0189?
Common possibilities include a failing fuel temperature sensor, loose or corroded connector, damaged wiring, poor terminal contact, or an intermittent open or short in the circuit.
Can a wiring problem cause P0189?
Yes. An intermittent open, short, damaged conductor, loose terminal, or poor connector connection can cause the ECM/PCM to see an unstable fuel-temperature signal.
What does P0189 mean on a Duramax?
On applicable Duramax applications, P0189 indicates an intermittent fuel temperature sensor B circuit condition. The exact sensor and wiring must be identified using the specific Duramax engine's service information.
What does P0189 mean on an L5P Duramax?
On an applicable L5P Duramax, P0189 indicates an intermittent signal involving the fuel temperature sensor B circuit. Diagnosis should include live data, connector inspection, wiring checks, and sensor testing before replacing components.
What does P0189 mean on a Chevrolet?
On applicable Chevrolet vehicles, P0189 means the ECM/PCM has detected an intermittent signal from fuel temperature sensor B. The exact sensor location and circuit depend on the engine and model year.
Can vibration cause P0189?
Yes. Vibration can expose a loose terminal, broken conductor, damaged connector, or harness problem that may not be obvious during a stationary inspection.
Is P0189 a generic or manufacturer-specific code?
P0189 is a generic OBD-II powertrain code. However, the actual sensor location, circuit design, diagnostic thresholds, and repair procedure can vary between manufacturers and engines.
Final Result
P0189 is a generic OBD-II powertrain code meaning Fuel Temperature Sensor B Circuit Intermittent. It indicates that the ECM/PCM is receiving an unstable or intermittent signal from the fuel temperature sensor B circuit.
The most reliable diagnosis is to monitor OBD live data, inspect the connector and wiring, perform a controlled wiggle test, verify power, ground and signal circuits, and test the sensor before replacing parts.
On applicable Duramax, Chevrolet Duramax, and L5P Duramax vehicles, the exact sensor location and circuit should be confirmed from the engine-specific service information. An intermittent electrical connection should be considered carefully before replacing an expensive component.