P0702 Transmission Control System Electrical
OBD-II Trouble Code Technical Description
Transmission Control System Electrical
What does that mean?
This diagnostic trouble code (DTC) is a generic powertrain code, which means that it applies to all 1996-newer vehicles (Ford, Honda, Mazda, Mercedes, VW, etc.). Although generic, the specific repair steps may vary depending on make/model.
If I encounter 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 portion of the transmission control system. Only vehicles equipped with an automatic transmission should exhibit this code.
Most transmission controllers (for OBD-II equipped vehicles) are integrated into the PCM but there are some manufacturers that use a stand-alone transmission control module (TCM). Regardless of with which type of system a particular vehicle is equipped, transmission related codes are stored as P-codes. There will likely be other transmission control codes stored with the P0702.
Automatic transmissions are controlled electronically in OBD-II equipped vehicles. A control module, controller area network (CAN), numerous sensors and solenoids, a powerful hydraulic pump, and a hydraulic valve body are vital to the operation of the electronically controlled transmission.
Input voltage signals from engine and transmission sensors are received by the transmission controller. Throttle angle, engine RPM, engine load percentage, and coolant temperature are among the engine sensor inputs. Helping to monitor pump pressure, transmission input speed (RPM), transmission output speed (RPM), shifter position, vehicle speed, torque converter lock-up percentage, and transmission temperature are the transmission sensor inputs. These input signals are used by the transmission controller to map shift strategy and electronic pump pressure parameters. The electronic pressure control valve regulates pump pressure and keeps the transmission shifting efficiently. Shifting would instantly become extremely harsh, and driveline components could be damaged, if maximum pump pressure were to be applied directly to the valve body. Up and down shifts are accomplished with electronically controlled solenoids that operate spring-loaded ball valves. These valves restrict and release high pressure fluid as desired. 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 is used to transmit data between the TCM (where applicable) and the PCM. Data (including stored codes) may also be transmitted to other controllers via the CAN. Among the information shared between controllers is transmission input and output speed (RPM), vehicle speed, and transmission temperature. Anti lock braking systems, electronic traction control systems, and electronic stability control systems all utilize this data for comparison purposes. This code is usually only stored if other electrical transmission control codes are present.
Symptoms & Severity
If, you have noticed that your transmission shifts more harshly than normal after this code is stored, it may be due to the transmission control system being placed in limp-in mode. Transmission pump pressure is dramatically increased in this mode. Limp-in mode is not meant 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
Potential causes for this code to set are:
Diagnostic and Repair Procedures
A good starting point is always to check for technical service bulletins (TSB) for your particular vehicle. Your issue may be a known issue with a known fix put out by the manufacturer and can save you time and money during diagnosis.
A vehicle service manual (or the equivalent), a scanner, and a digital volt/ohmmeter will be helpful when diagnosing a code P0702.
I would start with a visual inspection of transmission control wiring and connectors. Next, I’d test the battery, check battery cables, and battery terminal ends.
I normally proceed by connecting the scanner to the vehicle diagnostic connector and retrieving all stored codes and freeze frame data. I write this information down and save it for later.
If the code/s immediately reset, return to your recorded freeze frame data. Begin by diagnosing the code that was stored first and diagnose/repair all other stored transmission control codes before attempting to diagnose the P0702.
Additional diagnostic notes:
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"Delete Error Code Permanently, Disable DTC Error Code Function for p0702 in the ECU"
In extreme cases, we even have the option to permanently remove the specific DTC p0702 and disable the function of the specific error code in the ECU. All other fault code functions will then continue to work to protect the engine. This is different from clearing an error code with a diagnostic device. We have the option to permanently remove the function of the specific error code, so that it never comes back. Also emergency running that occurs on the specific error code can be solved in most cases.
Of course we prefer to first try to solve the cause of the error code, but sometimes the only solution is to permanently disable the DTC function of p0702.
