What does it mean?
This diagnostic trouble code (DTC) is a generic powertrain code, meaning it applies to all vehicles made from 1996 onward (Ford, Honda, Mazda, Mercedes, VW, etc.). Although generic, the specific repair steps may vary by make/model.
If I encounter a malfunction indicator light (MIL) and a stored code P0702, it means 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 have this code.
Most transmission controllers (for OBD-II equipped vehicles) are integrated into the PCM, but some manufacturers use a standalone transmission control module (TCM). Regardless of which 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 P0702.
Automatic transmissions are electronically controlled in OBD-II equipped vehicles. A control module, a controller area network (CAN), numerous sensors and solenoids, a powerful hydraulic pump, and a hydraulic valve body are all essential to the operation of the electronically controlled transmission.
Voltage input signals from the 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. Monitoring pump pressure, transmission input speed (RPM), transmission output speed (RPM), gear lever position, vehicle speed, torque converter lockup 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 settings. The electronic pressure control valve regulates pump pressure and keeps the transmission shifting efficiently. Shifting would instantly become extremely harsh and transmission components could be damaged if maximum pump pressure were applied directly to the valve body. Upshifts and downshifts are accomplished with electronically controlled solenoids that actuate spring-loaded ball valves. These valves restrict and release high-pressure fluid as desired. The torque converter clutch (TCC) solenoid controls the torque converter lockup percentage.
The CAN is a complex system of electrical wiring and connectors used to transmit data between the TCM (if applicable) and the PCM. Data (including stored codes) may also be transmitted to other controllers via the CAN. Among the information shared between controllers are 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 use this data for comparison purposes. This code is usually only stored if other electrical transmission control codes are present.
Symptoms
and severity
If you have noticed that your transmission is shifting more harshly than normal after this code is stored, it may be because the transmission control system is placed in limp-in mode. Transmission pump pressure is significantly increased in this mode. Limp-in mode is not intended for long-term use. If your vehicle has stored a P0702 code, it should be addressed immediately.
Symptoms of a P0702 code may include:
Erratic transmission shifting patterns
Transmission failure to shift at all
Decreased fuel efficiency
Other transmission-related codes
Causes
Causes
for setting this code may include:
Transmission sensor failure
Open or shorted circuits in the transmission control system
Faulty transmission controller or PCM programming error
Diagnostic and repair procedures
A good starting point is always to check for technical service bulletins (TSBs) for your particular vehicle. Your problem may be a known issue with a known fix released by the manufacturer and can save you time and money when diagnosing.
A vehicle service manual (or equivalent), a scan tool, and a digital volt/ohmmeter will be helpful when diagnosing a P0702 code.
I would start with a visual inspection of the transmission control wiring and connectors. Then I would test the battery, check battery cables and battery terminal ends.
I normally proceed by connecting the scan tool to the vehicle’s 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, refer back to your saved freeze frame data. Begin by diagnosing the code that was stored first and diagnose/repair any other stored transmission control codes before attempting to diagnose P0702.
Additional diagnostic notes:
The internal transmission control wiring harness is often damaged by extremely sharp edges, porous surfaces, and excessive temperatures found inside the transmission case
Performing transmission maintenance at recommended intervals can increase longevity
Diagnose and repair all other transmission codes before diagnosing this code