P0185 - Fuel Temperature Sensor 2 Circuit

The P0185 diagnostic trouble code (DTC) indicates a problem within the fuel temperature sensor 2 circuit. This sensor plays a crucial role in modern vehicle fuel management systems, providing the engine control unit (ECU) with information necessary for optimizing fuel delivery and engine performance. Understanding the cause and implications of P0185 is vital for proper diagnosis and repair.

Table: P0185 Fuel Temperature Sensor 2 Circuit - Comprehensive Information

Topic	Description	Possible Causes	Symptoms
Definition	The Engine Control Unit (ECU) has detected a malfunction in the electrical circuit associated with the Fuel Temperature Sensor 2. This circuit monitors the temperature of the fuel, typically after it has passed through the fuel cooler (if equipped) or returned to the fuel tank. Sensor 2 is often located in the fuel return line or near the fuel tank.	N/A	N/A
Sensor Function	Fuel Temperature Sensor 2 measures the temperature of the fuel. The ECU uses this data to adjust fuel injection timing, air-fuel ratio, and other engine parameters to optimize performance and reduce emissions. This is especially important in diesel engines where fuel temperature affects fuel viscosity and atomization. In some vehicles, it also helps prevent fuel vapor lock in hot weather.	N/A	N/A
Location	The location of Fuel Temperature Sensor 2 varies depending on the vehicle make and model. It's typically found: 1) In the fuel return line, close to the fuel tank; 2) Integrated within the fuel tank assembly; 3) After a fuel cooler (if equipped); 4) In rare cases, near the fuel injectors but in a return circuit. Consult your vehicle's service manual for the exact location.	N/A	N/A
Circuit Malfunction Types	The P0185 code can indicate several types of circuit malfunctions: 1) Open Circuit: A break in the wiring, preventing the signal from reaching the ECU. 2) Short to Ground: The signal wire is contacting the vehicle's chassis, causing a low voltage reading. 3) Short to Voltage: The signal wire is contacting a power source, causing a high voltage reading. 4) High Resistance: Corrosion or loose connections are increasing the resistance in the circuit, weakening the signal. 5) Out-of-Range Signal: The sensor is sending a signal that is either too high or too low for the expected range.	Faulty Fuel Temperature Sensor 2: The sensor itself has failed internally. Damaged Wiring: Corroded, broken, or shorted wires in the sensor circuit. Loose or Corroded Connectors: Poor electrical connections at the sensor or ECU. ECU Malfunction: (Rare) The ECU is not processing the signal correctly. Fuel Cooler Issues: (If equipped) A malfunctioning fuel cooler could cause abnormal fuel temperatures. Fuel Tank Issues: Debris or contamination in the fuel tank impacting the sensor. Aftermarket Modifications: Incorrectly installed or incompatible aftermarket fuel system components.	Check Engine Light (MIL) Illumination: This is the most common symptom. Decreased Fuel Efficiency: The ECU may not be able to optimize fuel delivery. Poor Engine Performance: Engine may experience hesitation, stalling, or rough idling. Difficulty Starting: Especially in cold weather. Increased Emissions: Improper fuel mixture can lead to higher emissions. Fuel Tank Pressure Issues: In some cases, can be linked to fuel tank pressure control.
Diagnostic Steps	1) Visual Inspection: Check the sensor, wiring, and connectors for any visible damage. 2) Scan Tool Data: Use a scan tool to read the fuel temperature sensor 2 value. Compare it to the actual fuel temperature. 3) Wiring Diagram: Consult a wiring diagram for your vehicle to identify the correct wires. 4) Multimeter Testing: Test the sensor's resistance and voltage. Check for continuity in the wiring. 5) Connector Testing: Check for voltage and ground at the sensor connector. 6) ECU Testing: (Last Resort) If all other tests pass, the ECU may be faulty.	N/A	N/A
Common Mistakes	1) Replacing the Sensor Without Diagnosing: The sensor may not be the problem. Always test the wiring and connectors first. 2) Ignoring Wiring Damage: Corrosion or broken wires can cause intermittent problems. 3) Using Incorrect Wiring Diagrams: Always use a wiring diagram that is specific to your vehicle. 4) Assuming ECU Failure: ECU failure is rare. Rule out all other possibilities first. 5) Neglecting Fuel System Condition: Contaminated fuel or a clogged fuel filter can indirectly affect the sensor's performance.	N/A	N/A
Related Codes	P0180 (Fuel Temperature Sensor A Circuit), P0181 (Fuel Temperature Sensor A Circuit Range/Performance), P0182 (Fuel Temperature Sensor A Circuit Low Input), P0183 (Fuel Temperature Sensor A Circuit High Input), P0186 (Fuel Temperature Sensor B Circuit Range/Performance), P0187 (Fuel Temperature Sensor B Circuit Low Input), P0188 (Fuel Temperature Sensor B Circuit High Input)	N/A	N/A
Typical Repair Costs	Sensor Replacement: $50 - $200 (including the sensor and labor). Wiring Repair: $50 - $300 (depending on the extent of the damage). ECU Replacement: $500 - $2000 (including the ECU and programming). These are estimates and can vary based on location, vehicle make/model, and shop rates.	N/A	N/A

Detailed Explanations

Definition: The P0185 code signals that the vehicle's ECU has identified an issue within the electrical circuit connected to the Fuel Temperature Sensor 2. This sensor's primary function is to monitor the temperature of the fuel, typically after it has passed through a fuel cooler (if equipped) or returned to the fuel tank. The ECU uses this information to optimize fuel delivery and engine performance.

Sensor Function: Fuel Temperature Sensor 2 measures the temperature of the fuel, providing crucial data to the ECU. This information allows the ECU to make adjustments to fuel injection timing, air-fuel ratio, and other engine parameters. In diesel engines, fuel temperature is particularly important as it affects fuel viscosity and atomization, which are critical for efficient combustion. In gasoline engines, the sensor can help prevent fuel vapor lock in hot weather.

Location: The location of Fuel Temperature Sensor 2 is vehicle-specific. Common locations include:

In the fuel return line, often close to the fuel tank.
Integrated within the fuel tank assembly.
After a fuel cooler (if the vehicle is equipped with one).
In rare cases, near the fuel injectors but in a return circuit. Always consult your vehicle's service manual for the precise location.

Circuit Malfunction Types: The P0185 code can arise from various circuit malfunctions:

Open Circuit: A break in the wiring, preventing the signal from reaching the ECU.
Short to Ground: The signal wire comes into contact with the vehicle's chassis, resulting in a low voltage reading.
Short to Voltage: The signal wire touches a power source, leading to a high voltage reading.
High Resistance: Corrosion or loose connections increase resistance in the circuit, weakening the signal.
Out-of-Range Signal: The sensor sends a signal that is either too high or too low for the expected range.

Possible Causes: Several factors can trigger the P0185 code:

Faulty Fuel Temperature Sensor 2: The sensor itself has failed internally.
Damaged Wiring: Corroded, broken, or shorted wires in the sensor circuit.
Loose or Corroded Connectors: Poor electrical connections at the sensor or ECU.
ECU Malfunction: (Rare) The ECU is not processing the signal correctly.
Fuel Cooler Issues: (If equipped) A malfunctioning fuel cooler could cause abnormal fuel temperatures.
Fuel Tank Issues: Debris or contamination in the fuel tank impacting the sensor.
Aftermarket Modifications: Incorrectly installed or incompatible aftermarket fuel system components.

Symptoms: The presence of a P0185 code may manifest in the following symptoms:

Check Engine Light (MIL) Illumination: The most common and obvious symptom.
Decreased Fuel Efficiency: The ECU may not be able to optimize fuel delivery.
Poor Engine Performance: Engine may experience hesitation, stalling, or rough idling.
Difficulty Starting: Especially in cold weather.
Increased Emissions: Improper fuel mixture can lead to higher emissions.
Fuel Tank Pressure Issues: In some cases, can be linked to fuel tank pressure control.

Diagnostic Steps: Diagnosing the P0185 code involves a systematic approach:

Visual Inspection: Thoroughly inspect the sensor, wiring, and connectors for any visible damage, such as corrosion or broken wires.
Scan Tool Data: Use a scan tool to read the fuel temperature sensor 2 value and compare it to the actual fuel temperature.
Wiring Diagram: Consult a wiring diagram specific to your vehicle to identify the correct wires in the sensor circuit.
Multimeter Testing: Use a multimeter to test the sensor's resistance and voltage. Also, check for continuity in the wiring.
Connector Testing: Check for proper voltage and ground at the sensor connector.
ECU Testing: (Last Resort) If all other tests pass, the ECU may be faulty, although this is rare.

Common Mistakes: Avoid these common mistakes when troubleshooting a P0185 code:

Replacing the Sensor Without Diagnosing: The sensor may not be the root cause of the problem. Always test the wiring and connectors first.
Ignoring Wiring Damage: Corrosion or broken wires can cause intermittent problems and should be carefully inspected.
Using Incorrect Wiring Diagrams: Always use a wiring diagram that is specific to your vehicle make, model, and year.
Assuming ECU Failure: ECU failure is a relatively rare occurrence. Rule out all other potential causes before suspecting the ECU.
Neglecting Fuel System Condition: Contaminated fuel or a clogged fuel filter can indirectly affect the sensor's performance.

Related Codes: The following codes are often related to P0185 and may provide additional diagnostic information:

P0180 (Fuel Temperature Sensor A Circuit)
P0181 (Fuel Temperature Sensor A Circuit Range/Performance)
P0182 (Fuel Temperature Sensor A Circuit Low Input)
P0183 (Fuel Temperature Sensor A Circuit High Input)
P0186 (Fuel Temperature Sensor B Circuit Range/Performance)
P0187 (Fuel Temperature Sensor B Circuit Low Input)
P0188 (Fuel Temperature Sensor B Circuit High Input)

Typical Repair Costs: Repair costs can vary widely depending on the cause and the extent of the damage:

Sensor Replacement: $50 - $200 (including the sensor and labor).
Wiring Repair: $50 - $300 (depending on the extent of the damage).
ECU Replacement: $500 - $2000 (including the ECU and programming).

These are estimates and can vary based on location, vehicle make/model, and shop rates.

Frequently Asked Questions

What does the P0185 code mean? The P0185 code indicates a problem with the fuel temperature sensor 2 circuit, meaning the ECU has detected an issue with the sensor's signal. This sensor measures the temperature of the fuel, typically in the return line or near the fuel tank.

Where is Fuel Temperature Sensor 2 located? The location varies by vehicle, but it's often found in the fuel return line, integrated into the fuel tank, or after a fuel cooler (if equipped); always check your vehicle's service manual. Consulting the vehicle's service manual is crucial for accurate identification.

Can I drive with a P0185 code? While you can usually drive with a P0185 code, it's not recommended for extended periods. The ECU may not be able to optimize fuel delivery, potentially leading to reduced fuel efficiency and poor engine performance.

What are the common causes of P0185? Common causes include a faulty fuel temperature sensor 2, damaged wiring, loose connectors, or, rarely, a faulty ECU. Always perform a thorough diagnosis to pinpoint the exact cause.

How do I fix a P0185 code? Fixing a P0185 code involves diagnosing the problem (sensor, wiring, connectors), repairing or replacing the faulty component, and clearing the code. Using a scan tool and a wiring diagram is highly recommended.

Conclusion

The P0185 diagnostic trouble code indicates a malfunction in the fuel temperature sensor 2 circuit, impacting fuel management and engine performance. Thorough diagnosis and repair, focusing on the sensor, wiring, and connectors, are essential for resolving this issue and restoring optimal vehicle operation.