The P1399 diagnostic trouble code (DTC) indicates an intermittent fault within the circuit of the Wheel Speed Sensor 2 - G - Sensor. This sensor plays a critical role in various vehicle systems, including Anti-lock Braking System (ABS), Traction Control System (TCS), and Electronic Stability Program (ESP). Understanding the causes, symptoms, and troubleshooting steps associated with this code is crucial for maintaining vehicle safety and performance.
P1399 - Wheel Speed Sensor 2 - G - Sensor Circuit Intermittent: A Detailed Overview
| Category | Description | Possible Causes |
|---|---|---|
| Sensor Identification | Refers to the wheel speed sensor located at "Wheel 2", often the left rear wheel. The "G" sensor component refers to the sensor's ability to detect lateral acceleration (G-force). | Incorrect sensor identification during diagnosis; Misunderstanding of the sensor's location. |
| Circuit Intermittency | The fault is not constant, but occurs sporadically. This can make diagnosis challenging. | Loose wiring connections; Corroded terminals; Damaged wiring harness; Intermittent sensor failure; Temperature-related issues (expansion/contraction affecting connections); Vibration affecting connections. |
| Sensor Function | Measures the rotational speed of the wheel and lateral acceleration. This information is vital for ABS, TCS, and ESP to function correctly. | Failure to accurately measure wheel speed or lateral acceleration will disable or degrade the performance of safety systems. |
| Possible Causes | A range of issues, from simple wiring problems to a failing sensor, can trigger this code. | Faulty Wheel Speed Sensor 2 (including G-sensor component); Damaged or corroded wiring and connectors; Open or shorted circuits in the wheel speed sensor wiring; Loose connections; Damaged reluctor ring/tone wheel; Improper wheel bearing installation; Faulty ABS control module (rare). |
| Symptoms | Noticeable effects on vehicle handling and braking performance. | ABS warning light illumination; TCS warning light illumination; ESP warning light illumination; Reduced or non-functional ABS; Reduced or non-functional TCS; Reduced or non-functional ESP; Erratic braking; Unstable handling, especially during cornering or braking; Cruise control malfunction. |
| Diagnostic Tools | Necessary for accurately pinpointing the cause of the code. | OBD-II scanner capable of reading live data; Multimeter for testing voltage and resistance; Wiring diagrams specific to the vehicle; Oscilloscope (optional, for advanced troubleshooting). |
| Diagnostic Steps | A systematic approach is essential for effective troubleshooting. | Visual inspection of the sensor, wiring, and connectors; Checking for corrosion or damage; Testing the sensor's resistance and output voltage; Checking the wiring harness for shorts or open circuits; Monitoring live data from the sensor using a scan tool; Performing a wiggle test on the wiring harness to identify intermittent connections. |
| Repair Procedures | Vary depending on the root cause of the problem. | Replacing the faulty wheel speed sensor; Repairing or replacing damaged wiring and connectors; Cleaning corroded terminals; Replacing a damaged reluctor ring/tone wheel; Re-seating loose connections; Replacing the ABS control module (last resort, after all other possibilities have been ruled out). |
| Related Codes | Other codes may be present, providing further clues to the problem. | C0037 (Wheel Speed Sensor 2 Circuit); C003A (Wheel Speed Sensor 2 Signal Erratic); Other ABS, TCS, and ESP related codes. |
| Vehicle Specificity | Troubleshooting steps and component locations can vary significantly between vehicle makes and models. | Always consult the vehicle's service manual for specific instructions and diagrams. |
| "G" Sensor Significance | The integrated G-sensor (lateral acceleration sensor) adds a dimension to the wheel speed data. It helps the vehicle understand not just wheel speed, but also how the vehicle is moving laterally. | The "G" sensor data is particularly important for advanced stability control systems that predict and prevent skids before they happen. A fault here can lead to inaccurate stability control interventions. |
| Interference Issues | Other electrical components or physical obstructions can interfere with the sensor or its wiring. | Check for aftermarket accessories (e.g., aftermarket lighting, audio systems) that may be interfering with the sensor wiring. Ensure nothing is physically obstructing the sensor or its tone ring. |
| Reluctor Ring/Tone Wheel Condition | The reluctor ring, also known as the tone wheel, is a toothed ring that rotates with the wheel. The sensor reads the teeth to determine wheel speed. | Damaged, corroded, or missing teeth on the reluctor ring will cause inaccurate readings. Inspect the reluctor ring carefully for any signs of damage. |
| Wheel Bearing Play | Excessive wheel bearing play can affect the sensor's ability to accurately read wheel speed. | Check for excessive wheel bearing play. If present, replace the wheel bearing. |
Detailed Explanations
Sensor Identification: The P1399 code specifically points to "Wheel Speed Sensor 2 - G - Sensor." "Wheel 2" typically refers to the left rear wheel. The integrated "G" sensor measures lateral acceleration, providing critical information for advanced stability control systems. Misidentifying the sensor location will lead to wasted time and incorrect repairs. Confirm the sensor location in your vehicle's service manual.
Circuit Intermittency: The intermittent nature of the fault means the problem doesn't occur constantly. This makes diagnosis more challenging as the fault may not be present when testing. This can be caused by a loose connection that only breaks contact under certain conditions (e.g., vibration, temperature change).
Sensor Function: Wheel speed sensors are crucial components of modern vehicle safety systems. They measure the rotational speed of each wheel, providing data to the ABS, TCS, and ESP systems. The integrated G-sensor measures lateral acceleration, providing even more data for the stability control system to work effectively. Without accurate wheel speed and lateral acceleration data, these systems cannot function correctly, compromising vehicle safety.
Possible Causes: The P1399 code can be triggered by various issues. A faulty wheel speed sensor is a common culprit, but damaged wiring, corroded connectors, a damaged reluctor ring, or even a faulty ABS control module can also be responsible. Thoroughly investigating each possibility is essential for accurate diagnosis.
Symptoms: The symptoms of a P1399 code can be noticeable and impact vehicle safety. The ABS, TCS, and ESP warning lights may illuminate on the dashboard. The ABS, TCS, and ESP systems may be disabled or function erratically. This can lead to reduced braking performance, unstable handling, and increased risk of accidents. In some cases, cruise control may also malfunction.
Diagnostic Tools: Several diagnostic tools are necessary for accurately diagnosing the P1399 code. An OBD-II scanner that can read live data is essential for monitoring the wheel speed sensor's output. A multimeter is needed for testing voltage and resistance in the wiring harness. Wiring diagrams specific to the vehicle are crucial for identifying the correct wires and connectors. An oscilloscope can be helpful for advanced troubleshooting, allowing you to visualize the sensor's signal.
Diagnostic Steps: A systematic approach is essential for diagnosing the P1399 code. Start with a visual inspection of the sensor, wiring, and connectors, looking for any signs of damage or corrosion. Test the sensor's resistance and output voltage to determine if it is functioning correctly. Check the wiring harness for shorts or open circuits. Monitor live data from the sensor using a scan tool to see if the signal is erratic or missing. Perform a wiggle test on the wiring harness to identify intermittent connections.
Repair Procedures: The repair procedures for a P1399 code vary depending on the root cause of the problem. If the wheel speed sensor is faulty, it needs to be replaced. Damaged wiring and connectors should be repaired or replaced. Corroded terminals should be cleaned. A damaged reluctor ring needs to be replaced. Loose connections should be re-seated. Replacing the ABS control module should be considered as a last resort, after all other possibilities have been ruled out.
Related Codes: The presence of other diagnostic trouble codes can provide valuable clues to the underlying problem. Codes related to the wheel speed sensor circuit (e.g., C0037, C003A) or other ABS, TCS, and ESP codes can help narrow down the possibilities.
Vehicle Specificity: Troubleshooting steps and component locations can vary significantly between vehicle makes and models. Always consult the vehicle's service manual for specific instructions and diagrams. This will ensure you are testing the correct components and following the recommended procedures.
"G" Sensor Significance: The "G" sensor (lateral acceleration sensor) integrated into the wheel speed sensor adds a crucial dimension to the wheel speed data. It helps the vehicle understand not just how fast the wheel is spinning, but also how the vehicle is moving laterally. This is particularly important for advanced stability control systems that predict and prevent skids before they happen. A fault in the "G" sensor can lead to inaccurate stability control interventions, potentially compromising vehicle safety.
Interference Issues: External factors can sometimes interfere with the proper functioning of the wheel speed sensor. Aftermarket accessories, such as aftermarket lighting or audio systems, can sometimes interfere with the sensor wiring, causing erratic readings. Physical obstructions can also interfere with the sensor or its tone ring. Carefully inspect the area around the sensor for any potential sources of interference.
Reluctor Ring/Tone Wheel Condition: The reluctor ring, also known as the tone wheel, is a toothed ring that rotates with the wheel. The wheel speed sensor reads the teeth on the reluctor ring to determine the wheel's speed. If the reluctor ring is damaged, corroded, or has missing teeth, it will cause inaccurate readings and trigger the P1399 code. Inspect the reluctor ring carefully for any signs of damage.
Wheel Bearing Play: Excessive wheel bearing play can affect the sensor's ability to accurately read wheel speed. If the wheel bearing is worn or damaged, it can allow the wheel to wobble, causing the sensor to produce inaccurate readings. Check for excessive wheel bearing play and replace the wheel bearing if necessary.
Frequently Asked Questions
What does the P1399 code mean? The P1399 code indicates an intermittent fault in the circuit of the Wheel Speed Sensor 2 - G - Sensor. This sensor is vital for ABS, TCS, and ESP functionality.
Where is Wheel Speed Sensor 2 located? Wheel Speed Sensor 2 typically refers to the left rear wheel speed sensor. Always consult your vehicle's service manual for confirmation.
Can I drive with the P1399 code? Driving with the P1399 code is not recommended, as it can affect the performance of your ABS, TCS, and ESP systems, potentially compromising vehicle safety.
How do I fix the P1399 code? Fixing the P1399 code involves diagnosing the cause of the intermittent fault and then repairing or replacing the faulty component, such as the sensor, wiring, or connector.
How much does it cost to fix the P1399 code? The cost to fix the P1399 code varies depending on the cause of the problem and the labor rates in your area. Replacing the sensor is typically less expensive than replacing the ABS control module.
Conclusion
The P1399 diagnostic trouble code signifies an intermittent issue with the Wheel Speed Sensor 2 - G - Sensor circuit, impacting vital vehicle safety systems. Thorough diagnosis and repair are crucial to restore proper functionality and ensure safe driving.