A slipping transmission is never a good sign. Generally, any error in shifting gears warrants a trip to your mechanic. The code P0734 is one of the many OBD-II codes related to this issue. If your scan tool reads this code, it pays to know what it means and how to address it. Below is an informative guide to help you understand code P0734 better.
What Does the P0734 Code Mean?
Diagnostic trouble code (DTC) P0734 stands for “Gear 4 Incorrect Ratio.” It is triggered once your powertrain control module or PCM detects that the RPM difference between the rotational speed of your input speed sensor and the transmission output speed sensor is greater than specified when your vehicle is in the 4th gear.
This error code often indicates that your transmission is slipping. It usually happens when your vehicle is shifting to 4th gear or even when driving at steady speeds
Automatic transmissions use multiple gear ratios to manipulate engine output. Your vehicle’s PCM or transmission control module (TCM) uses the data, such as information regarding throttle position vs. vehicle speed, to determine when to shift up and down between gears.
The data collected from different sensors are also used to check if all transmission components are working as they should. For example, the engine speed is typically calculated against the transmission speed sensor. This data is used to analyze gear ratio and detect torque converter slip.
Once your PCM detects that the data does not match the expected value, it will most likely trigger DTC P0734 and illuminate the check engine light.
Note: The definition of code P0734 may be different depending on the vehicle manufacturer. Consult the appropriate repair manual or repair database for the exact code definition.
What are the Possible Causes of the P0734 Code?
Error code P0734 can be triggered due to several reasons. Here are some of the possible causes of this code:
- Low transmission fluid
- Defective 4th gear-related shift solenoid
- Mechanical failure in the transmission
- Malfunctioning transmission control module (rare)
- Faulty valve body
- Blocked hydraulic passages due to dirty transmission fluid
What are the Common Symptoms of the P0734 Code?
Here are some of the common symptoms you should watch for in relation to the code:
- Check engine light
- Inability to shift to 4th gear/delayed shift
- Transmission slipping
- Decreased fuel economy
How to Diagnose the P0734 Code
Diagnosing code P0734 isn’t easy. Since this code can be triggered due to several causes, it may be difficult to pinpoint the underlying fault that is causing it. If you’re not well-versed with auto repair, it is best to leave the job to a mechanic.
However, if you have great DIY repair skills, you may handle the task yourself. Consult your manufacturer’s repair manual for the diagnostic steps that are fit for your vehicle.
How to Fix the P0734 Code
Just like any other diagnostic trouble code, there is no one fix for P0734 that can work for all makes and models. For example, repair steps for a P0734 in Dodge may not be the same for a P0734 in Subaru. Again, if you’re not well-versed with auto repair, it is best to take your vehicle to your auto repair shop for proper diagnosis and repair.
If you’re determined to fix this code yourself, you can use online auto repair manuals and guides to help you identify the repair steps compatible with your make and model. You may get an ALLDATA single-vehicle subscription, which should be useful in fixing this code and other issues with your car you may potentially face in the future.