P0734 on Acura
Gear 4 Incorrect Ratio
P0734 on Acura vehicles indicates gear 4 incorrect ratio. Au7o has documented this code across 3 Acura models — most commonly on CL, MDX, TL. This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode. Typical repair costs on Acura range from $2,500 to $6,500, depending on the specific model and root cause.
Common Causes of P0734
- •Low or degraded/burnt transmission fluid
- •Slipping clutch packs or worn friction elements in 4th gear
- •Stuck or faulty shift solenoid
- •Valve body / internal hydraulic leak or restriction
- •Worn or failing torque converter
- •Faulty input or output speed sensor
- •Internal mechanical wear (bands, planetary gears)
P0734 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 MDX(1 issue)
- ZF 9-Speed Transmission Hesitation, Hard Shifts and Stalling (2016-2019 MDX)2016-2019
The ZF 9HP 9-speed automatic introduced on the 2016 MDX suffers from documented hesitation, harsh shifts, lurching, and unexpected downshifts/deceleration. Drivers report the vehicle hesitating from a stop, banging into gear, or briefly losing power. Software miscommunication between TCM, ECM and throttle control is the alleged root cause; a class action was filed alleging Honda knew of the defect from 2015.
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 P0734 across all makes →Frequently Asked Questions
What does P0734 mean on Acura?▼
P0734 stands for "Gear 4 Incorrect Ratio." This code means the Transmission/Powertrain Control Module detected an incorrect gear ratio in 4th gear. The module continuously compares input shaft speed to output shaft speed; if the ratio in 4th gear doesn't match the expected value, it sets P0734. This usually indicates the transmission is slipping or not fully engaging 4th gear due to a hydraulic, friction, or solenoid problem. Symptoms include slipping, flaring RPM, harsh or missed shifts, and possibly limp mode. On Acura specifically, this code is documented across 3 models.
What causes P0734 on Acura vehicles?▼
Common causes on Acura: Low or degraded/burnt transmission fluid, Slipping clutch packs or worn friction elements in 4th gear, Stuck or faulty shift solenoid, Valve body / internal hydraulic leak or restriction, 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 P0734 on a Acura?▼
Repair costs on Acura range from $2,500 to $6,500, depending on the specific model and root cause.
Which Acura models have P0734 documented?▼
Au7o has documented P0734 on 3 Acura models: CL, MDX, TL.