Error Code P0701 is defined as Transmission Control System Range/Performance. This is a generic trouble code, meaning it applies to all vehicles equipped with the OBD-II system, especially those made since 1996 up to present. This includes vehicle models from but not limited to Ford, Honda, Mazda, Mercedes Benz, Volkswagen, etc. Specifications on the definition, troubleshooting, and repairs, of course, vary from one make and model, and powertrain configuration.
If the vehicle shows up this error code, this means the PCM (powertrain control module, also known as ECM or engine control module in other vehicle makes) has determined a malfunction in the TCM (transmission control system). This type of code is exclusive to vehicles with automatic transmission.
Most controllers are integrated into the PCM. Some, however, uses a stand-alone TCM. With this, Transmission related codes are as P-codes regardless of the type of system a specific vehicle is equipped, meaning there are no T-codes. When Error Code P0701 is stored, it’s highly possible it comes with other transmission control codes.
OBD-equipped vehicles control the automatic transmission electronically. This includes a control module, CAN (controller area network), multiple sensors and solenoids, a powerful hydraulic pump, and a hydraulic valve body.
The transmission controller gets its input voltage signal from the sensors of both engine and transmissions. Engine sensor inputs include (but not limited to) engine RPM, throttle, angle, coolant temperature, and load percentage. Transmission sensor input, on the other hand, monitors the transmission input speed (RPM), transmission output speed (RPM), pump pressure, vehicle speed, shifter position, transmission temperature, torque converter lock-up percentage, and more. With this, the transmission controller uses input signals from the map shift strategy and electronic pump pressure parameters. The transmission controller then uses these input signals to map shift strategy and electronic pump pressure parameters. The job of the electronic pressure control valve is to regulate the pump pressure and help keep the transmission shift smoothly. If maximum pump pressure were applied directly to the valve body, shifting could instantly become harsh and could lead to serious damages to the driveline. Electronically-controlled solenoids work with spring-loaded ball valves, restricting and releasing high-pressure fluid through the hydraulic circuits. This causes up and downshifts as desired. However, another solenoid controls the percentage of torque converter lock-up, increasing fuel efficiency and power to the pavement. The
CAN is actually a complex system of connectors and wires used to transmit data from the TCM (where applicable) all the way to the PCM. The data (this includes stored codes) may also be shared with another controller through CAN. Transmission input and output speeds (RPM), transmission temperature, and vehicle speed are all shared between different controllers. This data is then used for comparison for various systems, including electronic traction control systems, anti-lock braking systems, and electronic stability control systems, etc.
Error Code P0701 is pretty unique, as it’s usually only stored if the other transmission-related codes are present. These codes can be related to mechanical or electrical problems.
If Error Code P0701 is stored, then harsh shifting in the transmission may be noticed. This is due to TCM being in limp-in mode. In which case, transmission pump pressure is increased dramatically, which is dangerous in the long run. Other common symptoms include:
- Failure of transmission to shift
- Erratic shifting patterns
- Transmission slippage
- Delayed transmission engagement
- Increase in fuel consumption
Other transmission related codes may be present as well.
There are many possible causes for this code, some include:
- Use of substandard transmission fluid
- Low level of transmission fluid
- Failed transmission sensor
- Open or shorted circuits in the transmission control system
- Defective torque converter
- Failed mechanical (internal) transmission
- Faulty transmission controller
- Defective or programming error in PCM
How to Check
As with most codes, checking with a TSB (technical service bulletin) is a good starting point to diagnose this code. Other things you need include the basics, such as a scanner, DVOM (digital volt/ohmmeter), transmission gauge, and vehicle service manual (or equivalent).
Start the diagnosis with a visual inspection of the control wirings and connectors. Also, make sure to check the battery, including the battery cables and terminal ends.
Then, connect the scanner to the vehicle diagnostic connector and retrieve all stored codes, including their freeze frame data. Take note of this information.
The usual cause of transmission failure is due to bad fluid level and condition. Thus, it should be checked as well. Make sure you follow the manufacturer’s specifications for checking the transmission fluid level.
If the fluid has burnt smell, then you can suspect mechanical failure, and this requires a complete transmission rebuild and a new torque converter. If the fluid level is more than a quart low, refill the transmission with a transmission fluid (recommended by the manufacturer) and start the engine. Then, inspect the transmission, transmission cooler, and cooler hoses/lines for any signs of leakage. Repair as necessary.
Take the vehicle for a test drive to see if the code comes back. If the code does NOT come back, then it must be related to the low fluid condition, and you’ve solved the problem.
However, if the code comes back, record the freeze frame data, then proceed on diagnosing the code that was stored first. Diagnose and repair all other transmission codes stored before attempting to diagnose the P0701.
How to Fix
- Repair or replace faulty wiring, components, or connectors
- Repair any detected fluid leaks
- For vehicles with a manual transmission, replace the faulty PCM
- Fill the transmission to the right fluid level before taking the vehicle for a test drive
- Replace faulty sensors, switches, and solenoids
One of the most common mistakes when addressing this code is completely rebuilding the transmission when the problem lies in less expensive parts.
As part of rebuilding the transmission, many mechanics replace the torque converter, making the repair more expensive.