P0700: Transmission Control System (MIL Request)
The transmission control unit has stored a fault and asked the engine control unit to switch on the check engine light.
Normal risk
Depends on the transmission fault. Read the transmission module.
Short answer · Can I keep driving with P0700?
Depends on the actual fault. If the gearbox shifts normally, drive gently to a workshop. If it is stuck in one gear, limit driving.
What does P0700 mean?
Code P0700 is a notice: the transmission control unit has its own fault code stored. Read the transmission module to find it.
On its own P0700 says nothing about the actual problem. Shifting, fluid and other transmission codes give the full picture.
Clearing P0700 from the engine control unit does not remove the fault stored in the transmission module.
What the car does when the code is set
The check engine light comes on. Depending on the transmission fault, shifting may be normal, harsh or delayed, or the transmission may stay in one gear (limp mode).
How the system works
An automatic transmission has its own control unit that reads speed sensors, the selector position and pressure sensors, and controls shifting through solenoids. When it detects a fault that can affect emissions, it asks the engine control unit to light the check engine lamp. Because the engine control unit stores a code for that request, a basic scanner often shows only this code, while the detailed code stays in the transmission control unit.
Common symptoms
Possible causes
Listed without ranking. The cause on your car depends on make, engine and mileage — see the maker notes below.
- Fault in the transmission control systemThis code only reports that the transmission control unit has stored its own fault.
- Low or old transmission fluidOften found together with shifting codes.
- Sensor or solenoid faultSpeed sensors, pressure solenoids and wiring.
- Communication problemBetween the engine and transmission control units.
How it is diagnosed
- Read the transmission control unitUse a scan tool that reads the transmission module: the real cause is stored there.
- Check the fluidCheck level and condition as the service data describes.
- Follow the specific codeDiagnose the code from the transmission module.
- Clear and test-driveClear codes from both modules and test-drive.
Questions about P0700
Does P0700 need a special scanner?
A scanner that can read the transmission module is needed to see the real fault code.
Why does my basic scanner only show this code?
Many simple scanners read only the engine control unit. A scanner that reads the transmission module shows the real fault code.
Is P0700 a transmission failure?
Not necessarily. It only reports that the transmission control unit stored a fault. The real code there shows what is wrong.