AutoCodes – GMC – P0730 GMC

P0730 GMC Code - Incorrect Gear Ratio

Quick Answer

This diagnosis monitors the actual gear position by checking the torque converter slip ratio calculated by the Transmission Control Module (TCM) as follows: Torque converter slip ratio = A x C/B A: Output shaft revolution signal from the speed sensor (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 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: P0730 GMC indicates Incorrect Gear 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 3,956

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 26, 2020

Description
Step-by-Step Diagnostic Guide
Possible Causes
How To Fix
Tech Notes
Cost to Diagnose
Comments
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Code P0730 GMC Description

This diagnosis monitors the actual gear position by checking the torque converter slip ratio calculated by the Transmission Control Module (TCM) as follows:
Torque converter slip ratio = A x C/B
A: Output shaft revolution signal from the speed sensor (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 supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.
The Diagnostic Trouble Code (DTC) will set when the TCM has detected that the transmission is trying to mechanically shift to a lower gear than intended.

OBDII Code P0730 GMC - Incorrect Gear Ratio - AutoCodes.com — P0730 GMC Code - Incorrect Gear Ratio

What does this mean?

What are the Possible Causes of the DTC P0730 GMC?

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

How to Fix the DTC P0730 GMC?

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 P0730 GMC 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.