Incorrect Gear Ratio
What does P0730 mean?
The P0730 code means the vehicle's onboard diagnostic system has detected: Incorrect Gear Ratio. This is a critical severity code.
Common Symptoms
- Check Engine Light illuminated
- Transmission slipping badly
- Vehicle stuck in limp mode
- RPM flare with no acceleration
- Harsh or no shifting
Probable Causes (Ranked by Likelihood)
- Worn clutch packs or bands inside the transmission Very High
- Low or contaminated transmission fluid High
- Faulty shift solenoid Moderate
- Damaged torque converter Low
Step-by-Step Diagnostic Procedure
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Check transmission fluid level and condition immediately
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Monitor input and output speed sensor ratios in each gear -- compare to specification
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Check for additional shift solenoid codes
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Perform a line pressure test to check internal hydraulic pressure
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If fluid is burnt and gear ratios are incorrect, internal transmission repair or rebuild is likely needed
Frequently Asked Questions
Can I drive with code P0730?
Do not drive. An incorrect gear ratio indicates the transmission is slipping or not engaging properly. Continued driving can cause catastrophic transmission failure.
Does P0730 mean I need a new transmission?
Not always, but often. If the cause is a worn clutch pack or band, a transmission rebuild or replacement is typically necessary. If a solenoid or valve body is the cause, repair may be less extensive.
How is gear ratio measured for P0730?
The TCM compares input shaft speed to output shaft speed. The calculated ratio should match the expected gear ratio. When the ratio deviates beyond a threshold, the code is set.