B2871 Mercury Code - Left Rear Tire Pressure Sensor Fault
Quick Answer
The Tire Pressure Monitor (TPM) system monitors the air pressure in the 4 road tires with wheel-mounted tire pressure sensors. Common causes include Low tire pressure, Tire pressure sensor is missing or damaged, Spare tire is installed as a road wheel. Severity is High - diagnose this code as soon as possible. Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
- What it means
- B2871 Mercury indicates Left Rear Tire Pressure Sensor Fault.
- Common causes
- Common causes include Low tire pressure, Tire pressure sensor is missing or damaged, Spare tire is installed as a road wheel.
- Severity
- High - diagnose this code as soon as possible.
- Can I drive?
- Driving is not recommended if the warning light is flashing, the engine runs poorly, or safety-related symptoms are present.
Code B2871 Mercury Description
Each tire pressure sensor transmission is compared against a low-pressure limit (pressure listed on vehicle certification label minus 25 percent, which will be about 6-9 psi). If it is determined that the tire pressure has fallen below this limit, the SJB sends a message to the instrument cluster, which then illuminates the low pressure warning indicator and displays the appropriate message(s) in the message center (if equipped).
What are the Possible Causes of the DTC B2871 Mercury?
- Low tire pressure
- Tire pressure sensor is missing or damaged
- Spare tire is installed as a road wheel
- Incorrect tire pressure sensor is installed
- Tire pressure sensor installed incorrectly
- Faulty Left Rear Tire Pressure Sensor
How to Fix the DTC B2871 Mercury?
Review the 'Possible Causes' above and visually examine the corresponding wiring harness and connectors. Check for damaged components and inspect connector pins for signs of being broken, bent, pushed out, or corroded.
Code Tech Notes
What is the Cost to Diagnose the Code?
Labor: 1.0
To diagnose the B2871 Mercury code, it typically requires 1.0 hour of labor. Rates vary by location, vehicle, and shop. Many shops charge between $80–$150 per hour; dealerships and metro areas may be higher, independents may be lower.
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Frequently Asked Questions about B2871 Mercury Code
1. What does the OBDII code B2871 mean for a Mercury vehicle?
The code B2871 indicates a fault with the left rear tire pressure sensor, meaning it’s not transmitting data correctly or is malfunctioning.
2. What are common symptoms of the B2871 code in a Mercury?
Symptoms may include a tire pressure warning light on the dashboard, inaccurate tire pressure readings, or no reading for the left rear tire.
3. What causes the B2871 code to appear?
Causes can include a dead sensor battery, a damaged tire pressure sensor, interference with the signal, or a problem with the vehicle's TPMS module.
4. Can I drive my Mercury with the B2871 code?
Yes, but it’s not recommended to ignore it since you won’t receive accurate tire pressure readings, which could lead to unsafe driving conditions.
5. How do I fix the B2871 code on a Mercury?
The most common fix is to replace the left rear tire pressure sensor. Make sure the new sensor is properly programmed and calibrated.
6. How is the B2871 code diagnosed?
A mechanic will use a TPMS scan tool to check the functionality of the left rear sensor and verify if it's transmitting data correctly.
7. How much does it cost to repair the B2871 code?
Replacing a tire pressure sensor typically costs between $50 and $200, depending on the sensor and labor charges.
8. Can a dead sensor battery cause the B2871 code?
Yes, a dead battery inside the tire pressure sensor is a common cause of this code.
9. Do I need to replace all four sensors if one has failed?
Not necessarily. However, if the other sensors are old, it might be a good idea to replace them to avoid future issues.
10. Will resetting the TPMS clear the B2871 code?
Resetting the TPMS may temporarily clear the fault, but if the left rear sensor is defective, the code will likely return.
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