P0731 on Acura
Gear 1 Incorrect Ratio
P0731 on Acura vehicles indicates gear 1 incorrect ratio. Au7o has documented this code across 2 Acura models — most commonly on CL, TL. 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. Typical repair costs on Acura range from $2,500 to $4,500, depending on the specific model and root cause.
Common Causes of P0731
- •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
P0731 on Acura by Model
Acura CL(1 issue)
- 3.0CL automatic transmission slips and fails — flush is forbidden, filter is not serviceable1997-1999
The 1997-1999 3.0CL uses an automatic transmission specific to its V6 model family (the 2.2CL/2.3CL 4-cylinder variants do NOT share this transmission and are not affected). Owners and independent transmission shops widely report failures: slipping under load, not shifting out of 1st until warm, harsh shifts, and eventually total failure. Reports of repeat failures are common. NOTE: this transmission failure pattern is more severe and better documented on the 2nd-gen 3.2CL (2001-2003) than on the 1st-gen 3.0CL; the 1st-gen exhibits the same underlying weakness but at lower failure rates. A critical maintenance detail: this transmission has minimal internal filtration, and the filter is not serviceable without complete teardown. Owners who power-flush a slipping unit dislodge clutch debris and accelerate the failure rather than fix it.
Acura TL(1 issue)
- 1999 3.2TL 5-speed auto was the start of the famous Acura V6 transmission failures1999
1999 was the launch year of the 2nd-gen TL with the 3.2L J32A V6 and a new 5-speed automatic. This transmission family turned into one of the worst Acura defects of the early 2000s — torque converter failure, 3rd-gear clutch pack burn-up, blocked oil passages from debris, and complete failure became common. American Honda extended the transmission and torque converter warranties in 2003 (per TSB 02-027). The 1996-1998 TL uses the older 4-speed automatic which is generally reliable; the failure pattern is specifically the 5AT introduced for 1999. If you are car-shopping a 1999 TL, the model year alone does not tell you which transmission you have — the early-1999 carryover may have the older 4AT while the mid-year 2nd-gen launch got the 5AT. Check the build date and trans serial to know.
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View P0731 across all makes →Frequently Asked Questions
What does P0731 mean on Acura?▼
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 Acura specifically, this code is documented across 2 models.
What causes P0731 on Acura vehicles?▼
Common causes on Acura: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P0731 on a Acura?▼
Repair costs on Acura range from $2,500 to $4,500, depending on the specific model and root cause.
Which Acura models have P0731 documented?▼
Au7o has documented P0731 on 2 Acura models: CL, TL.