P0734 means Gear 4 Incorrect Ratio. In fourth gear, the ratio between input and output shaft speeds does not match what fourth gear should produce, which usually means a clutch or band applied in fourth gear is slipping. It is a generic OBD-II code, so the definition is the same on any make, but the most likely cause varies by engine; confirm with a scan tool and the service information for your vehicle before buying parts.
What P0734 means
Electronically controlled automatics are run by a transmission control module (TCM), a separate box or part of the engine computer. It reads speed sensors, the range sensor and fluid temperature to decide when to shift, and drives solenoids that apply clutches and the torque converter clutch. Many basic code readers only show the generic P0700; a scan tool that reads the transmission module shows the specific fault. Check fluid level and condition first, since low or burnt fluid causes many transmission codes.
P0734 symptoms
- Engine speed flaring in fourth gear
- Delayed or harsh shifts
- Limp mode
- Burnt fluid smell
Common causes of P0734
- Low or degraded fluid
- Worn clutch pack or band used in fourth gear
- A worn or burnt overdrive clutch, band or 3-4 clutch, depending on the design
- Low line pressure from a worn pump, a clogged filter or a pressure control fault
- A faulty input or output speed sensor giving a false ratio
How to diagnose P0734
- Check transmission fluid level and condition first
- Confirm both speed sensor signals are clean before trusting the ratio
- Watch input and output speeds in fourth gear on a scan tool
- Check line pressure with a gauge
- Inspect the pan for friction material and metal
Can you drive with P0734?
Limit driving: slipping in fourth gear builds heat and debris quickly.
P0734 tips
On four-speed automatics, fourth is overdrive, and loss of fourth under load is a common sign of a worn overdrive band or clutch. Heavy towing in overdrive speeds that wear, which is why many owners tow in a lower gear or use tow/haul mode.
Will P0734 clear itself?
If the fault stops, the computer turns off the check engine light by itself after several drive cycles without seeing it again, and the code stays in memory as history for a while. Clearing P0734 with a scan tool after a repair is fine, but if the cause is still there the code returns, sometimes within one drive. Disconnecting the battery also clears codes on most vehicles, but it erases learned fuel trims and idle settings as well.
Related codes
| Code | Meaning |
|---|---|
| P0730 | Incorrect Gear Ratio |
| P0733 | Gear 3 Incorrect Ratio |
| P0735 | Gear 5 Incorrect Ratio |
Guides that help
- 4L60E rebuild or replace
- 4L60E upgrades
- transmission slipping
- transmission fluid color
- transmission rebuild vs replacement
When it is more than a sensor
If the fault turns out to be internal (worn clutches, a failed converter or a damaged valve body), compare a rebuild with a replacement in transmission rebuild vs replacement and transmission replacement cost, identify your unit with what transmission do I have?, and browse our transmissions.
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