P0733 on Mazda: How to Diagnose & Fix
Gear 4 Incorrect Ratio
1 Mazda model · 1 documented issue · 1 critical · $2,000-$3,800 repair
P0733 on Mazda by model: symptoms, diagnosis and fix
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.
Common Symptoms
- Overdrive (O/D OFF) light flashing
- Slipping between gears
- Failure to shift 3rd to 4th
- Harsh or erratic shifting
- Delayed engagement into drive/reverse
- Complete loss of forward drive
- Transmission fluid leaks
- Overheating fluid / burnt smell
How to Fix
Preventatively, service the fluid every 30k miles with the correct spec fluid and add an auxiliary transmission cooler; heat is the primary killer. Once slipping, flashing O/D light, or harsh/erratic shifting begins, a proper rebuild with an upgraded/updated valve body and clutch parts (or a quality remanufactured unit) is the accepted repair. A band-aid fluid change rarely saves a unit that is already slipping.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Valvoline MERCON V automatic transmission fluid, 1 quartOEMValvoline 896421
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Sources for this issue (4)
P0733 code reference
General diagnostic-code context. The code alone does not confirm a cause for your vehicle; use the applicable issue card and its sources.
Frequently asked questions
What does P0733 mean on a Mazda?
P0733 stands for "Gear 4 Incorrect Ratio." This code indicates the transmission control module found that the actual gear ratio in 4th gear is outside the acceptable range for that gear. It is detected by comparing transmission input speed against output speed while 4th gear is engaged. A mismatch typically signals the transmission is slipping in 4th gear or that a control/hydraulic fault is preventing proper engagement. On Mazda it is documented across 1 model: 626.
What are the most common causes of P0733?
The most common causes of P0733 are: Low or contaminated transmission fluid, Worn 4th-gear clutch packs or bands, Failing shift solenoid for 4th gear, Valve body or line pressure issues, Internal transmission mechanical wear, Restricted transmission filter, Faulty input or output speed sensor. The specific cause varies by vehicle.
How much does it cost to fix P0733 on a Mazda?
Published repair estimates on Mazda range from $2,000 to $3,800 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.
Looking for P0733 on a different make?
View P0733 across all makes →Content compiled with AI assistance using NHTSA complaints, TSBs, and owner reports. May contain errors. Always verify with your vehicle's service manual.