P0700
Transmission Control System (MIL Request).
- Generic
- Powertrain
- Generic code
- Medium severity
How this code is built
- P
- SystemPowertrain
- 0
- Defined bySAE, the same on every car
- 7
- AreaTransmission
- 00
- FaultThe specific fault in that area
What it means
P0700 is a generic code meaning the transmission control module (TCM) has stored a fault and asked the engine control unit to switch on the malfunction indicator lamp. It is only a request flag and does not identify the actual problem. The real fault is held as one or more separate transmission codes in the TCM, so these must be read to find the cause.
Symptoms
- Malfunction indicator lamp on, possibly with a transmission warning or gearbox fault message
- Harsh, delayed or flared gear changes
- Transmission stuck in one gear (limp mode) or unable to select certain gears
- Poor acceleration or higher fuel consumption
- Speedometer or gear indicator behaving erratically
- Car may refuse to move or shift out of park or neutral in more serious cases
Possible causes
- A stored transmission fault in the TCM, such as a shift solenoid, pressure control solenoid or speed sensor fault, that triggered the requestlikely
- Wiring or connector faults at the transmission, including chafed looms, corrosion or fluid-contaminated plugslikely
- Low, degraded or contaminated transmission fluid affecting hydraulic pressure and solenoid operationpossible
- Faulty input or output speed sensor, or a gear ratio or torque converter slip faultpossible
- Internal transmission wear or valve body fault (depends heavily on the transmission type and model)possible
- Low battery voltage or poor earth causing TCM communication or supply faultsrare
- Faulty TCM or outdated TCM software where a known issue is documented for that modelrare
How to diagnose
- Read all stored and pending codes from both the engine control unit and the TCM, as P0700 alone is not diagnostic, and record freeze frame data
- Check the transmission fluid level and condition where a dipstick or check procedure is provided, noting colour, smell and debris; follow the manufacturer's procedure for the model
- Inspect the transmission wiring, connectors and earths for damage, corrosion, leaks and loose pins
- Check battery condition and charging voltage, and look for any communication or low voltage codes
- Diagnose the specific TCM codes in order, using live data to check speed sensors, gear selected versus gear commanded and solenoid duty
- Check for relevant technical service bulletins or software updates for the vehicle and transmission
- Perform pressure or stall tests, or internal inspection, only if electrical checks are clear and the procedure is specific to the transmission fitted
How to fix
- Repair or replace damaged wiring, connectors or earths at the transmission
- Correct the fluid level or replace degraded fluid and filter using the specified type and procedure
- Replace the faulty sensor or solenoid identified by the specific TCM code
- Repair or replace the valve body or internal components if testing confirms mechanical or hydraulic wear
- Update or reprogramme the TCM software only if an outdated calibration is a known cause for the vehicle, or replace a confirmed faulty TCM
Can I keep driving?
Short, gentle driving may be possible if the car shifts normally, but get it checked soon because the underlying fault can worsen and damage the transmission. If it is in limp mode, slipping or shifting harshly, limit driving and have it recovered or inspected promptly.
Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.