Critical Role of the Sensor ⚠️
In this article, we will examine the Fault Code P1391 and its impact on your vehicle’s operation.
To better understand this code, it is essential to look at the operation of the speed sensor. The latter is crucial for the vehicle’s active safety, as it allows various systems to function effectively. For example, a faulty sensor can lead to a loss of vehicle control, especially in adverse weather conditions. Indeed, during emergency braking, if the sensor does not transmit the correct information, the ABS system will not function as intended, increasing the risk of an accident.
Furthermore, the wheel speed sensor 1 also plays a role in optimizing fuel consumption. When the vehicle is properly equipped with a functional sensor, the engine control unit can adjust the engine’s performance in real-time, thus contributing to better fuel economy. Therefore, a faulty wheel speed sensor can not only compromise your safety but also increase your operating costs related to fuel.
The wheel speed sensor 1 (usually the front left wheel) provides vital data for:
- ABS Braking (prevents wheel lock-up)
- Traction Control (prevents loss of grip)
- Directional Stability (ESC system)
- Vehicle Speed Calculation (speedometer, engine management)
Main Causes 🔧
The Fault Code P1391 indicates a problem related to the wheel speed sensor 1, which can affect the systems mentioned above.
| Frequency | Cause | Details |
|---|---|---|
| 45% | Sensor failure | Damaged magnet, burnt-out coil (overheating/corrosion) |
| 30% | Wiring problems | Cut wires, oxidized connectors (especially behind the wheel) |
| 15% | Dirty/damaged tone ring | Grease/metal debris on the reluctor |
| 7% | Excessive bearing play | Sensor-reluctor misalignment |
| 3% | ABS/ECM module failure | Rare – requires in-depth diagnosis |
It is also important to note that preventive sensor replacement can be beneficial. If you notice signs of failure, such as erratic behavior in the speedometer or warning lights illuminated, it is advisable to have the sensor inspected quickly. Indeed, this can help you avoid more costly repairs in the future and ensure your vehicle remains safe on the road.
The average lifespan of a wheel speed sensor is approximately 100,000 to 150,000 kilometers, but this can vary depending on several factors, including driving conditions and vehicle maintenance. Frequent driving in harsh conditions, such as muddy or snowy roads, can reduce the sensor’s lifespan. Therefore, it is wise to regularly check its condition, especially if you have noticed anomalies in the operation of your car’s safety systems.
Symptoms 🚨
- ABS + Traction Control warning lights illuminated on the dashboard
- ABS deactivated (traditional braking only → risk of hydroplaning)
- Loss of stability control (dangerous turns in wet weather)
- Erratic behavior of the speedometer
- ⚡ Excessive fuel consumption (the ECM poorly compensates for data loss)
Another symptom to watch for is an unexpected variation in the speed displayed on the dashboard. This may indicate that the sensor is not working correctly or that there is a problem with the wiring. For example, if you accelerate, but the speedometer remains stubbornly low, this warrants immediate investigation. Drivers should be attentive to these warning signs to avoid more serious problems on the road.
Specific Buick Diagnostic 🔍
Step 1: Visual Inspection
- Locate the front left wheel sensor (behind the brake disc)
- Check:
- Electrical connector (frequent corrosion on Buick Enclave/LaCrosse)
- Sensor/reluctor distance (0.5-1.5 mm max)
- Cleanliness of the tone ring (clean with degreaser if dirty)
Step 2: Electrical Tests
| Test | Tool | Normal Values |
|---|---|---|
| Resistance | Multimeter | 800-1400 Ω (depending on model) |
| AC Voltage | Oscilloscope (wheel rotating) | Sinusoidal signal > 0.5V |
| Continuity | Circuit tester | No breaks to ABS module |
During the visual inspection, it is also helpful to check the condition of other components associated with the safety systems, such as brake discs and pads. A braking system in good condition can compensate for some of the problems caused by a faulty speed sensor but should not be considered a long-term solution. Particular attention should be paid to the entire braking system to ensure vehicle safety.
Repairs & Costs 💰
| Problem | Solution | Average Cost |
|---|---|---|
| Faulty Sensor | Replacement (ACDelco/GM) | $80-150 + labor |
| Damaged Wiring | Harness repair | $100-200 |
| Tone Ring | Cleaning/replacement | $20-180 |
| ABS Module | Reprogramming/replacement | $300-800 |
⏱️ Intervention Time: 1h (diagnosis) + 1h (simple repair).
Safety Emergencies 🚨
Do not drive if:
- ABS + traction control warning lights are flashing
- Abnormal grinding noises at low speed
- Spongy brake pedal
→ Risk of complete deactivation of electronic aids!
In addition to electrical tests, it might be helpful to regularly monitor the vehicle’s performance over time. Noting changes in driving behavior can reveal trends that might indicate an emerging problem. For example, if you start to feel unusual vibrations while driving, this could be a sign that something else is wrong, possibly related to the speed sensor.
Electrical tests can also include evaluating the connections at the ABS module level, as connection problems can also disrupt the sensor’s operation. A multimeter can help you determine if the signal is being transmitted correctly. If the test reveals anomalies, it may be necessary to replace the wiring or connectors to restore optimal operation.
Pro Tips 🔧
When it comes to repairs, it is important to consider the warranties offered by the manufacturer on replacement parts. Sometimes, the initial cost of a high-quality sensor may be higher, but it is usually justified by increased durability and reliability. By investing in quality replacement parts, you can avoid recurring problems that could otherwise lead to additional costs in the long run.
- Universal Sensor: Avoid low-end parts (frequent calibration errors).
- Reset: After repair, clear codes via OBD-II + road test at 40 km/h.
- Sensitive Models: Buick Regal 2011-2017 (connector corrosion – seal with dielectric grease).
- Common Error: Confusing P1391 (circuit problem) with C1391 (internal ABS module fault).
📊 Statistic: 90% of P1391 codes on Buick are resolved by sensor replacement + reluctor cleaning.
Conclusion:
The P1391 code compromises active safety systems. Recommended procedure:
Replace the sensor if necessary → Reset the ECM
Do not ignore this code: a faulty ABS system triples the risk of accident in slippery conditions!
Check wiring and connector
Test the sensor (resistance/signal)
Clean the tone ring
In conclusion, it is essential to monitor the condition of your speed sensor and react quickly to signs of failure. Ignoring the Fault Code P1391 can have serious consequences for your safety and that of others on the road. In terms of prevention, regular maintenance and constant vigilance are your best allies to ensure your vehicle functions properly. Do not take a problem that may seem minor lightly, as it could quickly become a major danger. If you have any doubts, do not hesitate to consult a professional for a thorough diagnosis.