AutoCodes – BMW – P0734 BMW

P0734 BMW Code - Gear 4 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 (4th) 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: P0734 BMW indicates Gear 4 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 42,749

How popular is this code, among other codes? Medium

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
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
FAQs
Comments
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Code P0734 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 (4th) 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 P0734 BMW - Gear 4 Incorrect ratio - AutoCodes.com — P0734 BMW Code - Gear 4 Incorrect ratio

What does this mean?

What are the Possible Causes of the DTC P0734 BMW?

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

How to Fix the DTC P0734 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 P0734 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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Need Help with the Code?

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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 P0734 BMW Code

1. What does the OBDII code P0734 mean on a BMW?

P0734 indicates that the transmission control module (TCM) has detected an incorrect gear ratio in 4th gear, which may point to a mechanical, hydraulic, or electronic issue within the transmission system.

2. What are the common symptoms of the P0734 code in a BMW?

Symptoms may include poor acceleration, slipping in 4th gear, difficulty shifting gears, reduced fuel efficiency, the transmission going into limp mode, and the illumination of the check engine light.

3. What causes the P0734 code to appear on a BMW?

Common causes include low or dirty transmission fluid, a faulty transmission solenoid, worn clutch packs, internal transmission damage, or issues with the transmission control module (TCM) or its wiring.

4. Can I drive my BMW with the P0734 code active?

Driving with the P0734 code is not recommended, as it can lead to further transmission damage. It's best to address the issue as soon as possible to avoid costly repairs.

5. How is the P0734 code diagnosed on a BMW?

A mechanic will typically check the transmission fluid condition, scan the TCM for additional codes, inspect solenoids and wiring, and perform a road test to monitor gear ratio performance in 4th gear.

6. How do I fix the P0734 code on my BMW?

Fixes may include changing or topping off the transmission fluid, replacing faulty solenoids, repairing damaged wiring, or rebuilding the transmission if internal damage is severe.

7. Can low transmission fluid cause the P0734 code on a BMW?

Yes, low or contaminated transmission fluid can lead to improper hydraulic pressure, causing the transmission to struggle to maintain the correct gear ratio.

8. How much does it cost to repair a BMW with the P0734 code?

Repair costs can vary widely depending on the cause, ranging from $100 for a fluid change to several thousand dollars for a transmission rebuild or replacement.

9. Can a faulty transmission control module (TCM) trigger the P0734 code?

Yes, a malfunctioning TCM or its wiring can lead to incorrect gear ratio detection and trigger the P0734 code.

10. Will resetting the check engine light fix the P0734 code on a BMW?

Resetting the light without addressing the underlying issue will not fix the problem, and the code is likely to reappear. Proper diagnosis and repair are necessary.