AutoCodes – BMW – P0731 BMW

P0731 BMW Code - Gear 1 Incorrect ratio

Quick Answer

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows: Torque converter slip ratio = A x C/B A: Output shaft revolution signal from revolution sensor B: Engine speed signal from Engine Control Module (ECM) C: Gear ratio determined as gear position which TCM supposes If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. Common causes include Low transmission fluid level, Dirty transmission fluid, Shift solenoids. 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: P0731 BMW indicates Gear 1 Incorrect ratio.
Common causes: Common causes include Low transmission fluid level, Dirty transmission fluid, Shift solenoids.
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 16,801

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 Jun 14, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0731 BMW Description

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B
A: Output shaft revolution signal from revolution sensor
B: Engine speed signal from Engine Control Module (ECM)
C: Gear ratio determined as gear position which TCM supposes

If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.

OBDII Code P0731 BMW - Gear 1 Incorrect ratio - AutoCodes.com — P0731 BMW Code - Gear 1 Incorrect ratio

What does this mean?

What are the Possible Causes of the DTC P0731 BMW?

Low transmission fluid level
Dirty transmission fluid
Shift solenoids
Transmission mechanical problems
Transmission hydraulic control circuit

How to Fix the DTC P0731 BMW?

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 does this mean?

Code Tech Notes

Start by inspecting the transmission fluid level and condition, and change fluid if necessary.

What is the Cost to Diagnose the Code?

Labor: 1.0

To diagnose the P0731 BMW 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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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.

Frequently Asked Questions about P0731 BMW Code

1. What does the OBDII code P0731 mean on a BMW?

P0731 indicates that the transmission control module (TCM) has detected an incorrect gear ratio for first gear in the transmission.

2. What are the common symptoms of code P0731 in a BMW?

Symptoms may include poor acceleration, slipping in first gear, harsh shifting, the transmission stuck in limp mode, and the check engine light being illuminated.

3. What causes the P0731 code on a BMW?

Common causes include low or dirty transmission fluid, a faulty transmission control module, a damaged or worn-out transmission solenoid, mechanical issues within the transmission, or a malfunctioning speed sensor.

4. Can low transmission fluid cause the P0731 code in a BMW?

Yes, low or contaminated transmission fluid can cause the P0731 code because it may affect proper hydraulic pressure and gear engagement.

5. How can I fix the P0731 code on my BMW?

Start by checking and replacing low or dirty transmission fluid. If the issue persists, inspect the transmission solenoids, speed sensors, and internal transmission components. Seek professional diagnostics if needed.

6. Is it safe to drive a BMW with a P0731 code?

Driving with a P0731 code is not recommended as it can lead to further transmission damage or unsafe driving conditions due to poor gear performance.

7. How do speed sensors relate to the P0731 code on a BMW?

Speed sensors monitor gear ratios by measuring input and output shaft speeds. A faulty speed sensor can lead to incorrect ratio detection and trigger the P0731 code.

8. Can a software update fix the P0731 code in a BMW?

In some cases, a software update for the transmission control module may resolve the issue if the problem stems from incorrect programming.

9. How much does it cost to repair the P0731 code on a BMW?

Repair costs vary depending on the cause. Fluid replacement is inexpensive, but solenoid repairs, speed sensor replacements, or transmission overhauls can cost several hundred to thousands of dollars.

10. Will resetting the check engine light fix the P0731 code on a BMW?

Resetting the light without addressing the underlying issue will not fix the code. The problem will likely reappear until proper repairs are made.