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P0700 Severity
Identifying an OBD code is just the start of a complete diagnostic routine. Most trouble codes are caused by a sensor reporting a value that is out of range. Just replacing a sensor may not fix underlying issues. Be sure to understand the code, the part or system in your car that the code refers to, and the risks of delaying professional repair.
Proper diagnosis will save you time and money on unnecessary repairs.
Urgent codes indicate immediate action is necessary. These are urgent and significant malfunctions that can cause severe damage to the vehicle or harm the driver and passengers.
The automatic transmission matches the engine optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels. When the Transmission control module (TCM) detects an issue with the transmission, it will send a message to the engine computer (PCM) to set code P0700. Additional codes are usually stored in the TCM.
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OBD-II Code P0700 is defined as a Transmission Control System Malfunction
The purpose of the automatic transmission is to match the engine's optimum power and torque characteristics to the driver's desired rate of acceleration and speed by auto-selecting different gear ratios or 'speeds' to power the wheels.
When the code P0700 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is seeing greater than a specified RPM difference between the rotational speed of the Input RPM Sensor and the Transmission Output RPM Sensor. This can occur during shifting or when driving at steady speeds in the same gear. It often implies that the transmission is slipping.
When diagnosing a P0700 code, it is important to record the freeze frame information and then to duplicate the code setting conditions with a test drive. Pay close attention to the engine load, throttle position, RPM, and road speed because a P0700 can be difficult to detect.
One should monitor the RPM input speed and compare that to output speed RPM on a smooth, flat surface after the vehicle is warmed up and the fuel system is in a closed loop. Monitor how the Converter Lockup Solenoid responds to an increased amount of throttle. The Lockup Solenoid duty cycle should go to 0 percent when the Throttle Position Sensor is above 40 percent and should return to 100 percent when the throttle is returned back to 15 to 20 percent when going 45 mph +. The duty cycle should go to 0 percent whenever the throttle is fully released or when the vehicle has decelerated below 30 MPH. The Lockup Solenoid duty cycle should go to 0 percent whenever the brake pedal is applied, regardless of speed.
When looking at the Toque Converter RPM versus the Input Shaft RPM, observe if the scan tool data has a Converter Slip Speed PID or Parameter Identification. This can be very helpful in the diagnosis of an intermittent P0700. If the Lockup System is functioning correctly, the Slip Speed value should never be above 50 RPM. Try gently depressing the throttle on a gradual incline above 45 mph. When doing this, the Slip Speed should not increase. If it does and the Lockup Solenoid duty cycle is 100 percent—meaning it is fully applying the converter clutch—then you know you have a slipping Converter Clutch.
If the Slip Speed stays steady but the transmission Output Shaft Speed starts to decrease (along with the MPH), then you know that you have an internally slipping transmission, usually caused by worn Clutch Packs or Sprag 1-Way clutches. If the Slip Speed remains very high and the Lockup duty cycle is 100 percent, then it is likely that the Solenoid is defective, because the duty cycle is reporting that the PCM is commanding the Lockup System to apply, but there is no change. Even with worn out Converter Clutches, there is always some kind of Slip Speed reading. It may go very high whenever the throttle is applied, but there should be some kind of a RPM reduction between the Converter Speed and the Input Shaft speed that verifies the Lockup Solenoid and PCM are trying to do their jobs.