P0730 on Mazda
Incorrect Gear Ratio
P0730 on Mazda vehicles indicates incorrect gear ratio. Au7o has documented this code across 2 Mazda models — most commonly on 626, CX-90. This code means the transmission computer detected that the actual gear ratio (calculated from input vs. output shaft speeds) does not match what it should be for the commanded gear. In other words, the transmission isn't delivering the correct gear, which often shows up as slipping, flaring RPM during shifts, or being stuck in the wrong gear. It can stem from internal mechanical wear, low or contaminated fluid, or faulty solenoids and sensors. The vehicle may shift harshly or enter limp mode. Typical repair costs on Mazda range from $2,000 to $3,800, depending on the specific model and root cause.
Common Causes of P0730
- •Low or contaminated transmission fluid
- •Worn clutches or bands (internal slipping)
- •Faulty shift solenoids
- •Dirty or sticking valve body
- •Faulty input or output speed sensor
- •Internal hydraulic/line pressure problems
- •Torque converter problems
- •General high-mileage transmission wear
P0730 on Mazda by Model
Mazda 626(1 issue)
- CD4E 4-speed automatic transmission premature failure1993-1997
The Ford-designed CD4E automatic transaxle fitted to 1993-1997 (5th-gen GE) 626s with an automatic is one of the most notorious weak points of the car. It runs hot, has undersized clutch packs and a fragile forward-clutch/valve-body design, and commonly fails anywhere from 60,000-100,000 miles. Both the FS 2.0L I4 and KL 2.5L V6 automatic cars used it. Repair shops have reported very high failure rates and the NHTSA/CarComplaints logs are dominated by transmission complaints for these years. A primary root cause was an inadequate factory transmission cooling circuit (a poorly designed radiator that did a bad job cooling the ATF). There was no recall, so owners bore the cost. The 626/MX-6 community regards a manual-transmission car as far more reliable.
Mazda CX-90(1 issue)
- 8-Speed Automatic Transmission Jerkiness2024-2025
The new Aisin-sourced 8-speed automatic transmission in the CX-90 exhibits jerky low-speed shifts, particularly the 1-2 and 2-3 upshifts. The transmission hesitates during parking lot maneuvers and light throttle driving. This is Mazda's first use of this 8-speed longitudinal gearbox, and early calibration has been rough. Multiple TSBs and software updates have been released.
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View P0730 across all makes →Frequently Asked Questions
What does P0730 mean on Mazda?▼
P0730 stands for "Incorrect Gear Ratio." This code means the transmission computer detected that the actual gear ratio (calculated from input vs. output shaft speeds) does not match what it should be for the commanded gear. In other words, the transmission isn't delivering the correct gear, which often shows up as slipping, flaring RPM during shifts, or being stuck in the wrong gear. It can stem from internal mechanical wear, low or contaminated fluid, or faulty solenoids and sensors. The vehicle may shift harshly or enter limp mode. On Mazda specifically, this code is documented across 2 models.
What causes P0730 on Mazda vehicles?▼
Common causes on Mazda: Low or contaminated transmission fluid, Worn clutches or bands (internal slipping), Faulty shift solenoids, Dirty or sticking valve body, Faulty input or output speed sensor. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0730 on a Mazda?▼
Repair costs on Mazda range from $2,000 to $3,800, depending on the specific model and root cause.
Which Mazda models have P0730 documented?▼
Au7o has documented P0730 on 2 Mazda models: 626, CX-90.