P0730: Incorrect Gear Ratio
Updated November 12, 2026
The transmission computer compares input and output speeds (or engine speed and vehicle speed) to confirm the transmission is in the gear it commanded. P0730 means the ratio doesn't match the expected gear, which usually means the transmission is slipping or not fully engaging a gear.
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🔧 Want to check this yourself? An OBD2 scanner reads the code; models with live data also show the sensor readings used in the checks below. See code readers and scanners from $24.99 ↓ · Which scanner do I need?
Common causes
- Low, burnt or degraded transmission fluid
- A faulty shift solenoid or pressure control solenoid
- A clogged transmission filter or valve body problem
- Worn internal clutches or bands
- A faulty input or output speed sensor giving a false reading
Code meanings can vary slightly by manufacturer. Use these as a starting point and confirm with your vehicle's service information or a mechanic before replacing parts.
Symptoms
- Engine RPM flaring up without the car speeding up (slipping)
- Harsh, delayed or missed shifts
- The transmission stuck in one gear (limp mode)
- Check engine or transmission warning light
Is it safe to drive?
If the transmission is slipping, won't shift, is stuck in one gear or the car won't accelerate properly, stop driving and have it towed; continued slipping can destroy the transmission. If it shifts normally with a steady light, check the fluid right away, drive gently and get it diagnosed soon.
How to check it with a scanner
- Plug an OBD2 scanner into the port under the dashboard and read all stored codes and the freeze-frame data (the conditions when the code set).
- Check the transmission fluid level and condition using your vehicle's procedure; many must be checked warm with the engine running, and some sealed units need a shop. Keep hands clear of belts and the fan. Very dark or burnt-smelling fluid is a warning sign.
- Scan the transmission module for gear-specific ratio codes (P0731 to P0736) and solenoid or speed sensor codes; they narrow down the cause.
- If your scanner shows them, have a passenger compare input and output shaft speeds in live data during a drive.
- Use only the transmission fluid type your vehicle specifies.
- After a repair, clear the code and drive normally for a few days to confirm it doesn't come back.
A basic code reader shows the code; scanners with live data let you watch sensor readings, which is what you need for most of the checks above. See OBD2 scanners under $100.
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Questions
What does P0730 mean?
P0730 is the generic OBD2 code for "Incorrect Gear Ratio." The transmission computer compares input and output speeds (or engine speed and vehicle speed) to confirm the transmission is in the gear it commanded. P0730 means the ratio doesn't match the expected gear, which usually means the transmission is slipping or not fully engaging a gear.
Is it safe to drive with P0730?
If the transmission is slipping, won't shift, is stuck in one gear or the car won't accelerate properly, stop driving and have it towed; continued slipping can destroy the transmission. If it shifts normally with a steady light, check the fluid right away, drive gently and get it diagnosed soon.
How do I check P0730 myself?
Read the code and freeze-frame data with an OBD2 scanner, then: Check the transmission fluid level and condition using your vehicle's procedure; many must be checked warm with the engine running, and some sealed units need a shop. Keep hands clear of belts and the fan. Very dark or burnt-smelling fluid is a warning sign. Scan the transmission module for gear-specific ratio codes (P0731 to P0736) and solenoid or speed sensor codes; they narrow down the cause. If your scanner shows them, have a passenger compare input and output shaft speeds in live data during a drive. Use only the transmission fluid type your vehicle specifies.
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