AutoCodes – Generic – P1871

P1871 Code - Undefined Gear Ratio

Quick Answer

P1871 indicates Undefined Gear Ratio. Common causes for P1871 include wiring or connector problems, a faulty related sensor or actuator, and control module or calibration issues. 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: P1871 indicates Undefined Gear Ratio.
Common causes: Common causes for P1871 include wiring or connector problems, a faulty related sensor or actuator, and control module or calibration issues.
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.

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Code Popularity 11,119

How popular is this code, among other codes? Low

Repair Importance Level

Urgent (Diagnose now) (3 / 3)

Repair Difficulty Level

Advanced (Pro) (3 / 3)

What is this?

Table of contents Created and updated by William Orellana on Sep 25, 2019

Description
How To Fix
Cost to Diagnose
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Code P1871 Description

OBDII Code P1871 - Undefined Gear Ratio - AutoCodes.com — P1871 Code - Undefined Gear Ratio

How to Fix the DTC P1871?

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.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P1871 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.

Need more information about the P1871 code?

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Information for Specific Makes

P1871 Buick — Undefined Gear Ratio
P1871 Cadillac — Undefined Gear Ratio

About the author: William Orellana is a Master Mechanic and Mechanical Engineer with over 30 years of experience diagnosing and repairing vehicles. Learn more about his background.