Car & driving · Free
P0700: transmission control system malfunction
P0700 means the automatic gearbox control unit has found a fault and asked the engine computer to switch on the check engine light. The code itself is only a messenger: the real fault is a second, more specific code stored in the gearbox control unit.
- No account
- Runs on your device
- Phone & desktop
Check your car for P0700
Runs on your device
Connect your OBD2 adapter
- Plug the adapter into the OBD2 port – usually under the steering wheel, near the pedals.
- Switch the ignition on, or start the engine.
- Bluetooth adapter? Turn Bluetooth on. Nothing else to set up.
This browser cannot talk to OBD adapters. Use Chrome or Edge on Android, Windows or Mac – on iPhone, the free Bluefy browser works with Bluetooth LE adapters. The demo car works everywhere.
Wi-Fi adapters cannot work in a browser; Bluetooth LE, classic Bluetooth (on a computer) and USB adapters can.
Your car data stays on your device. The page talks to the adapter directly; codes, VIN and values are never uploaded.
Never use it while you drive. Set things up before you set off, or let a passenger handle the phone. Standard OBD2 reads engine and emissions data; ABS, airbag and coding need workshop equipment.
What P0700 means
In cars with an automatic gearbox, a separate transmission control module (TCM) monitors the gearbox: speed sensors, solenoids, fluid temperature and gear ratios. When it detects a fault that affects emissions, it tells the engine computer, which stores P0700 and turns on the check engine light.
P0700 alone says nothing about what is wrong. Some cars also report the specific transmission code, such as P0715 or P0750, through the standard OBD2 interface; others keep it in the gearbox unit, where only a scan tool that speaks the manufacturer’s protocol can read it.
Symptoms of P0700
- Harsh, late or erratic gear changes.
- The gearbox stays in one gear (limp mode), often third or second.
- Slipping: the engine revs but the car does not speed up.
- A gearbox warning on the dashboard.
Causes of P0700, cheapest first
Work down the list in order: the first checks cost little or nothing, the last ones are jobs for a workshop.
Low or old transmission fluid
Check the level as described in the owner’s manual, often with the engine running and warm. Dark, burnt-smelling fluid is a warning sign.
A weak battery or poor connections
Gearbox control units are sensitive to low voltage. Check the battery and the connectors at the gearbox.
A faulty speed or temperature sensor
Input and output speed sensors and the fluid temperature sensor fail fairly often and are relatively cheap.
Shift solenoids or the valve body
Solenoids control the gear changes; a stuck or failing one causes harsh or missing shifts.
Internal wear or a faulty control unit
Worn clutches or a failed transmission control module are the expensive end and need a workshop diagnosis.
Can you drive with P0700?
Drive gently, avoid long trips. If the gearbox shifts normally, short trips are usually fine. In limp mode, drive gently and only as far as necessary: forcing a slipping gearbox causes more damage. Have the gearbox control unit read soon.
Check P0700 with OBD Studio
Connect your adapter above, or try the demo car, then:
- In Fault codes, look for other P07xx codes: if your car reports them through OBD2, they name the actual fault.
- In Vehicle, see whether a Transmission control unit answered. If it did, its generic codes appear in the code list.
- Check Control module voltage in Live data: low voltage alone can trigger gearbox faults.
- If only P0700 is stored, have a workshop read the gearbox unit with a manufacturer-level tool.
More fault code guides
Each of these codes has its own page with causes ranked by cost and the checks that go with them.
- P0420Catalyst efficiency below threshold
- P0171System too lean
- P0300Random or multiple misfire
- P0455EVAP system large leak
- P0442EVAP system small leak
- P0128Engine warms up too slowly
- P0172System too rich
- P0401EGR flow too low
- P0101Air flow sensor implausible
- P0135Front O2 sensor heater
- P0016Crankshaft and camshaft out of step
- P0011Intake camshaft timing over-advanced
- P0141Rear O2 sensor heater
- P0113Intake air temperature sensor high
- P0457Fuel cap loose or missing
- P0299Turbo underboost
- P0087Fuel rail pressure too low
- P0562System voltage low
- U0100Lost communication with engine computer
More OBD Studio pages
Frequently asked questions
Can I fix P0700 by clearing it?
Clearing only switches off the light. If the gearbox fault is still there, the code returns. Find the specific transmission code first.
Why does my scanner show only P0700?
Because the details are stored in the gearbox control unit. Standard OBD2 sees the engine computer’s P0700 and, on some cars, generic gearbox codes; manufacturer codes need a brand-specific tool.
Does P0700 mean my gearbox is broken?
Not necessarily. Low fluid, a sensor or a wiring fault is far more common than internal damage. Have the specific code read before you think about a replacement.
Can I read P0700 without going to a workshop?
Yes. With any ELM327-compatible Bluetooth LE or USB adapter, OBD Studio on this page reads P0700 and every other stored code for free, shows the freeze frame and clears the code after the repair. Nothing to install, no account.
