The common symptoms of an onboard diagnostic code P0700 transmission control system malfunction include illumination of the check engine light, decreased fuel economy and difficulty shifting. In rare cases, the issue causes no symptoms, other than illuminating the check engine light. Some drivers note vehicle performance problems such as the vehicle dying when it comes to a stop after driving at highway speeds.
Problems likely to trigger the P0700 code include defective shift solenoids, a malfunctioning engine coolant sensor or a defective valve body. Operating the vehicle without servicing the transmission increases the chances of dirty transmission fluid restricting passages in the transmission, resulting in the problem code.
The sensors that send the P0700 code to the OBDII system monitor the speed of the input rotational speed of the transmission and its output. The difference often occurs when the transmission is shifting gears or the vehicle is operating at a constant speed in the same gear. A large difference between these two speeds often indicates that the transmission is slipping.
Because the problem affects the vehicle performance, it is often misdiagnosed as an engine misfire, drivetrain problem or an internal transmission problem. The issue is often difficult to replicate in the shop, adding to the issues of misdiagnosis.