P1390 - Wheel Speed Sensor 1 - G

Introduction

The P1390 diagnostic trouble code (DTC) indicates a problem within the wheel speed sensor circuit, specifically concerning the "G" sensor. This sensor, often integrated within the Anti-lock Braking System (ABS) or Electronic Stability Program (ESP), plays a crucial role in vehicle stability and braking performance. Understanding the causes, symptoms, and troubleshooting steps associated with this code is essential for maintaining vehicle safety and functionality. Addressing this code promptly is crucial to prevent potential safety hazards and ensure optimal vehicle handling.

Comprehensive Table: P1390 - Wheel Speed Sensor 1 - G - Sensor Circuit

Topic	Description	Possible Symptoms
Definition	The P1390 code signals a malfunction in the circuit of the "G" sensor associated with Wheel Speed Sensor 1. The "G" sensor typically refers to an accelerometer that detects the vehicle's acceleration and deceleration, contributing to ABS/ESP functionality. Wheel Speed Sensor 1 usually refers to the front left wheel. The code indicates that the signal from this sensor is either out of range, intermittent, or absent.	ABS warning light illumination; ESP/Traction Control light illumination; Reduced or disabled ABS/ESP/Traction Control functionality; Erratic braking performance; Unstable handling during acceleration/deceleration; Vehicle pulling to one side during braking; Potential increase in stopping distance; Hard shifting of automatic transmission
Possible Causes	Faulty Wheel Speed Sensor 1 (including integrated G sensor); Damaged or corroded wiring or connectors in the sensor circuit; Open or short circuit in the sensor wiring; Loose or disconnected wiring; Faulty ABS control module; Incorrect wheel alignment affecting sensor readings; Foreign object interference (debris, etc.) with the sensor or tone ring; Voltage supply issues to the sensor; Software issues in the ABS/ESP control unit; Mechanical damage to the wheel hub or bearing affecting sensor placement	Same as Possible Symptoms
Diagnostic Steps	Visual inspection of the wiring, connectors, and sensor for damage; Using a multimeter to test the sensor's resistance and voltage output; Checking the wiring diagram for the specific vehicle to identify the sensor circuit; Scanning the ABS/ESP control module for other related DTCs; Using a scan tool to monitor the sensor's data in real-time while driving; Performing a wiggle test on the wiring and connectors to check for intermittent issues; Checking the wheel bearing for excessive play; Inspecting the tone ring for damage or debris; Testing the power and ground circuits to the sensor; Consulting the vehicle's service manual for specific troubleshooting procedures	N/A (These are diagnostic procedures, not symptoms)
Repair Strategies	Replacing the faulty Wheel Speed Sensor 1 (including integrated G sensor); Repairing or replacing damaged wiring or connectors; Cleaning corroded connectors; Securing loose wiring connections; Replacing the faulty ABS control module (requires programming); Performing a wheel alignment; Removing any foreign objects interfering with the sensor; Repairing voltage supply issues; Flashing or reprogramming the ABS/ESP control module; Replacing a damaged wheel hub or bearing	Resolution of Possible Symptoms; ABS/ESP/Traction Control systems functioning properly; Stable and predictable braking performance; Improved vehicle handling

Detailed Explanations

Definition

The P1390 code is a diagnostic trouble code (DTC) that indicates a malfunction in the wheel speed sensor circuit, specifically related to the "G" sensor integrated within Wheel Speed Sensor 1. This sensor measures the vehicle's longitudinal acceleration and deceleration forces. Wheel Speed Sensor 1 usually refers to the front left wheel. The code suggests an issue with the sensor's signal, meaning it's either out of range, intermittent, or completely absent. This directly impacts the ABS/ESP system's ability to accurately assess vehicle dynamics and apply corrective braking forces.

Possible Causes

Several factors can trigger the P1390 code. A faulty wheel speed sensor itself is a primary suspect, especially if the integrated G sensor is malfunctioning. Damaged or corroded wiring and connectors in the sensor circuit can disrupt the signal transmission. An open or short circuit within the wiring can also prevent the sensor from functioning correctly. Loose connections are another common culprit, as they can cause intermittent signal loss. In rarer cases, a faulty ABS control module might misinterpret or fail to process the sensor's data. An incorrect wheel alignment can lead to inaccurate sensor readings, triggering the code. Foreign object interference (debris, etc.) with the sensor or tone ring can also disrupt the sensor's functionality. Issues with the voltage supply to the sensor can also cause malfunctions. Software glitches in the ABS/ESP control unit are possible, but less common. Finally, mechanical damage to the wheel hub or bearing can affect sensor placement and accuracy.

Diagnostic Steps

Diagnosing the P1390 code requires a systematic approach. Start with a visual inspection of the wiring, connectors, and sensor for any signs of damage or corrosion. Use a multimeter to test the sensor's resistance and voltage output, comparing the readings to the manufacturer's specifications. Consult the vehicle's wiring diagram to understand the sensor circuit layout. Use a scan tool to check for other related DTCs in the ABS/ESP control module. Monitor the sensor's data in real-time while driving the vehicle to identify any erratic or inconsistent readings. Perform a wiggle test on the wiring and connectors to check for intermittent issues. Check the wheel bearing for excessive play, as this can affect sensor alignment. Inspect the tone ring for damage or debris that might be interfering with the sensor. Test the power and ground circuits to the sensor to ensure proper voltage supply. Finally, consult the vehicle's service manual for specific troubleshooting procedures tailored to the vehicle model.

Repair Strategies

The repair strategy depends on the underlying cause of the P1390 code. Replacing the faulty wheel speed sensor (including the integrated G sensor) is often necessary if the sensor itself is malfunctioning. Repairing or replacing damaged wiring or connectors is crucial for restoring proper signal transmission. Cleaning corroded connectors can improve conductivity and eliminate signal disruptions. Securing loose wiring connections is essential for preventing intermittent issues. In rare cases, replacing the faulty ABS control module might be necessary, but this requires programming the new module to the vehicle. Performing a wheel alignment can correct any misalignment issues affecting sensor readings. Removing any foreign objects interfering with the sensor or tone ring can restore proper sensor functionality. Repairing voltage supply issues ensures the sensor receives adequate power. Flashing or reprogramming the ABS/ESP control module can resolve software glitches. Finally, replacing a damaged wheel hub or bearing can correct sensor placement and improve accuracy.

Frequently Asked Questions

What does the P1390 code mean? It signifies a problem in the wheel speed sensor 1 circuit, specifically related to the "G" sensor, indicating a malfunction in measuring acceleration/deceleration.
Can I drive with the P1390 code? While you can drive, it's not recommended. The ABS/ESP system may be compromised, leading to reduced braking performance and potential safety hazards.
Is the P1390 code serious? Yes, it can be serious as it affects the vehicle's stability and braking systems, potentially increasing the risk of accidents.
How do I fix the P1390 code myself? You can start by visually inspecting the wiring and connectors, but proper diagnosis often requires a scan tool and multimeter. Professional assistance is recommended for complex repairs.
How much does it cost to fix a P1390 code? The cost varies depending on the cause. Replacing a wheel speed sensor is typically less expensive than replacing the ABS control module. Expect to pay between $150 and $800, depending on the needed repair.

Conclusion

The P1390 diagnostic trouble code indicates a problem within the wheel speed sensor 1 circuit, specifically concerning the "G" sensor. Prompt and accurate diagnosis is critical to ensure the proper functioning of the ABS/ESP system, ultimately contributing to vehicle safety and optimal handling. It is recommended to consult a qualified mechanic for diagnosis and repair.