What the P0734 code means?
Utilizing the position of the throttle, engine load and speed, as well as vehicle speed, the vehicle computer determines the appropriate gear to shift into to maintain the desired speed and power in an automatic transmission. The P0734 trouble code develops when there is a problem shifting into fourth gear specifically. The vehicle's Engine Control Module (ECM), Transmission Control Module (TCM), or PCM, depending on the vehicle make and model, uses information from the transmission speed sensor, calculated against engine speed, to determine the proper gear ratio.
What causes the P0734 code?
Low or dirty transmission fluid
Mechanical failure inside transmission
Internal blockage inside transmission main control
Faulty Shift solenoid
What are the symptoms of the P0734 code?
These may vary from no detectable symptoms at all to a failure of the transmission to shift from (or into) any particular gear. Other symptoms may include harsh shifting, transmission slippage, transmission overheating, decreased fuel efficiency, a stored code, and possibly an illuminated malfunction indicator lamp. Other gear ratio codes often accompany this code.
Common mistakes when diagnosing the P0734 code:
Technicians report that more frequently than not, internal transmission failures cause this code, and shift solenoid malfunctions are diagnosed and solenoids are replaced in error.
What repairs can fix the P0734 code?
1. If upon inspection it is determined that the transmission has suffered damage due to a low fluid condition, the mechanic must first rebuild the transmission, perform a fluid flush, and replace the torque converter, before the transmission will perform properly.
2. If a rebuild and flush does not fix the problem, the problem might lie with the wiring or connectors. In this case, the mechanic should replace any damaged, or faulty, wiring or connectors. Most often, if damaged components are detected during this inspection, the full internal transmission harness needs replacing.