Technical Description of OBD-II Trouble Code
Electrical Issue in the Transmission Control System
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code that is applicable to all vehicles manufactured from 1996 onwards (Ford, Honda, Mazda, Mercedes, VW, etc.). Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
If I come across a malfunction indicator lamp (MIL) and a stored code P0702, it means that the powertrain control module (PCM) has detected a malfunction in the electrical part of the transmission control system. Only vehicles equipped with an automatic transmission should display this code.
Most transmission controllers for OBD-II equipped vehicles are integrated into the PCM, but there are some manufacturers that use a separate transmission control module (TCM). Regardless of the type of system a particular vehicle is equipped with, transmission-related codes are stored as P-codes. There will likely be other transmission control codes stored along with the P0702 code.
Automatic transmissions in OBD-II equipped vehicles are controlled electronically. A control module, controller area network (CAN), various sensors and solenoids, a powerful hydraulic pump, and a hydraulic valve body are essential for the operation of the electronically controlled transmission.
The transmission controller receives input voltage signals from engine and transmission sensors. These input signals include throttle angle, engine RPM, engine load percentage, and coolant temperature from the engine sensors. The transmission sensors provide input signals such as pump pressure, transmission input speed (RPM), transmission output speed (RPM), shifter position, vehicle speed, torque converter lock-up percentage, and transmission temperature. The transmission controller uses these input signals to determine shift strategy and electronic pump pressure parameters. The electronic pressure control valve regulates pump pressure to ensure efficient shifting. Electronically controlled solenoids operate spring-loaded ball valves to achieve upshifts and downshifts. The torque converter clutch (TCC) solenoid controls the percentage of torque converter lock-up.
The CAN is a complex system of electrical wiring and connectors that transmits data between the TCM (if applicable) and the PCM. Data, including stored codes, may also be transmitted to other controllers via the CAN. Transmission input and output speed (RPM), vehicle speed, and transmission temperature are among the information shared between controllers. Anti-lock braking systems, electronic traction control systems, and electronic stability control systems utilize this data for comparison purposes. This code is usually only stored if other electrical transmission control codes are present.
Symptoms & Severity
If you notice that your transmission shifts more harshly than usual after this code is stored, it may be due to the transmission control system entering limp-in mode. In this mode, transmission pump pressure is significantly increased. Limp-in mode is not intended for long-term use. If your vehicle has stored a code P0702, it should be addressed immediately.
Symptoms of a P0702 code may include:
Causes
Possible causes for this code to be set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) specific to your vehicle. Your issue may be a known problem with a known solution provided by the manufacturer, which can save you time and money during diagnosis.
When diagnosing a code P0702, a vehicle service manual (or equivalent), a scanner, and a digital volt/ohmmeter will be helpful.
Begin by visually inspecting the transmission control wiring and connectors. Next, test the battery, check battery cables, and inspect battery terminal ends.
Proceed by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. Write down this information and save it for later reference.
If the code/s immediately reset, refer to the recorded freeze frame data. Start by diagnosing the code that was stored first and diagnose/repair all other stored transmission control codes before attempting to diagnose the P0702 code.
Additional diagnostic notes:
