P0702 - TRANSMISSION CONTROL SYSTEM ELECTRICAL

Vehicle manufacturers have developed the monitoring of transmissions through different sensors, solenoids, and regulators, with which an efficient operation of the transmission is achieved. All these devices receive and send information to the TCM (Transmission Control Module).

The TCM, like any other module of the vehicle, receives feedback signals from the solenoids, and with this signal, it is possible to detect faults in one of the transmission components. In this case, the TCM will activate a DTC code. Specifically, the P0702 OBDII fault code shows that the transmission control system has experienced a malfunction.

How does the P0702 Generic Code work?

This code is usually only displayed on vehicles with automatic transmission. The majority of transmission controllers (for OBD-II equipped vehicles) are built into the PCM. However, some manufacturers employ a stand-alone TCM. Regardless of the kind of system, a specific vehicle is fitted with, the codes related to the transmission are stored as P codes.

On vehicles fitted with the OBD-II system, automatic transmissions are electronically driven. The control module, Controller Area Network (CAN), numerous sensors and solenoids, a high-powered hydraulic pump, and hydraulic valve body are essential to the proper performance of an electronically driven transmission.

The transmission controller gets input voltage signals from the engine and transmission sensors. Throttle angle, engine speed, engine load percentage, and coolant temperature inputs to the engine sensor. The transmission sensor inputs aid in tracking the pump pressure, transmission input speed (RPM), transmission output speed (RPM), switch position, vehicle speed, torque converter lockup percentage, and transmission temperature. These inputs are analyzed by the transmission controller to indicate shift strategies and electronic pump pressure parameters.

An electronic pressure regulating valve adjusts the pump pressure and guarantees the efficiency of gear shifts. If full pump pressure is directly delivered to the valve body, gear shifting will be instantaneously too harsh and transmission parts may be damaged. Up and downshifting is accomplished through electronically controlled solenoids that operate spring-loaded ball valves. These valves restrict and release fluid at high pressure at will. The torque converter clutch (TCC) solenoid fits the torque converter lock-up percentage.

CAN is a sophisticated system of wiring and connectors employed to pass data between the TCM (if applicable) and the PCM. Data (including stored codes) can also be passed to other controllers via CAN. The controllers exchange information on transmission input and output speed (rpm), vehicle speed, and transmission temperature. Anti-lock braking systems, electronic traction control systems, and electronic stability control systems rely on this data for cross-checking. This code is generally kept only when other electrical transmission control codes are in operation.

If you find that your transmission is shifting more sharply than normal after setting this code, it may be because the transmission control system is in idle mode. In this mode, the transmission pump pressure increases precipitously. Limp-in mode is not designed for extended use. If your vehicle has a P0702 code, detect the problem immediately.

• Check Engine lamp illuminated.
• Erratic gear changes.
• Noticeable increase in fuel consumption.
• Transmission slipping.
• Transmission-related trouble codes are set.

The reasons for setting the P0702 OBD2 diagnostic code are:

• The transmission fluid may be below the required level.
• One or more transmission sensors may be damaged.
• The transmission control circuit wires or connectors could have inconsistencies, causing a short or open circuit.
• The TCC (Torque Converter Clutch) could be in bad condition.