P0731 on Kia: How to Diagnose & Fix
Gear 1 Incorrect Ratio
1 Kia model · 1 documented issue · $400-$1,800 repair
P0731 on Kia by model: symptoms, diagnosis and fix
The A6MF-family 6-speed automatic can develop harsh or erratic shifting, hard 6-to-4 kickdown 'bang,' shift flares, brief neutral feel during up/downshifts, and torque-converter clutch (TCC) shudder. The root cause is wear of the reducing-valve bores in the valve body, which lets line pressure drift out of spec; neglected fluid (SP4-spec) accelerates the wear. A documented secondary fault is a valve-body bolt that can abrade the internal wiring harness, producing intermittent solenoid faults. This is a distinct transmission failure mode from the AWD rear-differential coupling noise already documented.
Common Symptoms
- Hard or jerky shifts
- 6-to-4 downshift bang/clunk
- RPM flare or neutral feeling between shifts
- Torque-converter shudder at light cruise
- Delayed engagement into Drive/Reverse
How to Fix
Start with a proper SP4-spec fluid service and a TCM software update if available. Persistent harsh shifting, gear-ratio or solenoid-performance codes are usually resolved by rebuilding or replacing the valve body (with the reducing valves/solenoids), and inspecting the internal harness for abrasion. In severe slip/shudder cases the torque converter is replaced.
What you need to fix it
Only diagnosis- and fitment-reviewed repair parts are linked here.
- Genuine Kia UM013-CH059 ATF Type 4(M) / SP-IV transmission fluidOEMKia UM013-CH059
Use only for a Kia-procedure fluid service after level, condition and transmission diagnosis Fitment/availability: 2017-2022 Kia Sportage QL six-speed automatic, both 2.4L GDI and 2.0L T-GDI; the current Kia guide lists total fill 7.1 qt…
As an Amazon Associate, we earn from qualifying purchases; other part links may also earn au7o a commission. Confirm fitment by VIN before buying.
Sources for this issue (2)
P0731 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 P0731 mean on a Kia?
P0731 stands for "Gear 1 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 1st gear. The module compares input (engine/turbine) speed to output shaft speed; when the car is commanded into 1st but the calculated ratio doesn't match the expected value, P0731 sets. This points to slipping, an incorrect shift, or a hydraulic/mechanical problem rather than just an electrical fault. You may feel slipping, harsh or delayed engagement, or the transmission may go into a limited 'limp' mode. On Kia it is documented across 1 model: Sportage.
What are the most common causes of P0731?
The most common causes of P0731 are: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction components, Stuck or faulty shift solenoid affecting 1st gear, Internal hydraulic leak / valve body fault, Worn or failing torque converter, Faulty input or output speed sensor, Mechanical wear (planetary gears, bands) inside the transmission. The specific cause varies by vehicle.
How much does it cost to fix P0731 on a Kia?
Published repair estimates on Kia range from $400 to $1,800 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 P0731 on a different make?
View P0731 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.