fault code guide
P0700: Transmission Control System Malfunction
This code means the gearbox computer has detected a fault and asked the main engine computer to turn on the warning light. Your car may shift roughly or enter limp mode to protect the transmission.
How it shows up: The amber engine management light will stay on, and an OBD scanner will read code P0700. You might also notice harsh shifting, slipping between gears, or the gearbox locking into a single gear.
Updated 9 November 2026
Can I keep driving?
Service soon
The car can usually be driven gently to a place of safety, but ignoring a gearbox fault risks permanent internal damage or sudden loss of drive.
What to do right now
- 1Pull over in a safe place if the gearbox is slipping severely or will not select a gear.
- 2Switch off the ignition, wait two minutes, and restart to see if the car resets from limp mode.
- 3Drive gently and avoid heavy acceleration, towing, or steep climbs while making your way to a garage.
Likely causes
Most likely first.
- Likely
Faulty shift solenoid or valve body problem
Electronic solenoids direct fluid to change gears, and if one sticks or burns out, the transmission control module flags an immediate error.
- Likely
Low or degraded transmission fluid
Automatic gearboxes rely on hydraulic fluid pressure to engage gears, so leaks or worn-out fluid cause slipping and prompt a trouble code.
- Possible
Damaged wiring harness or corroded connector
The wiring loom between the engine bay and the gearbox sits low down where road salt, water, or oil leaks can corrode electrical pins.
- Possible
Worn clutch packs or mechanical failure
Friction materials inside the gearbox wear over high mileages, causing internal slippage that the control module detects through speed sensors.
- Rare
Failing transmission control module
Internal electronic component failure inside the control unit can trigger false readings or lose communication with the main engine computer.
What you can check yourself
Park somewhere safe and level, engine off, before you start.
- 1
Inspect the ground for fluid leaks
Park on dry, level ground with the engine off. Look underneath the centre of the car for reddish, brown, or burnt-smelling oily puddles.
- 2
Check the transmission dipstick if fitted
Check your owner handbook first, as many modern cars have sealed units. If yours has a dipstick, check the level and wipe it on a clean white cloth to see if the fluid looks bright pink to red or dark and burnt.
- 3
Test 12-volt battery voltage
Low electrical voltage can confuse electronic modules and cause false transmission fault codes. A healthy battery should read around 12.6 volts with the engine off.
- 4
Scan for specific transmission sub-codes
P0700 is merely an alert code telling you that the gearbox computer has specific faults stored. Use an advanced diagnostic scanner capable of reading transmission modules to retrieve the exact secondary codes.
Rough cost to fix
Rough estimateTypical prices in Ireland (€) and the UK (£), from an independent garage up to a main dealer. The total bill depends entirely on whether the fault is an external sensor or fluid issue versus an internal mechanical failure requiring a gearbox overhaul.
Transmission fluid and filter service
- Do it yourself
- €70–180£60–160 in the UK
- At a garage
- €180–380£150–330 in the UK
Gearbox shift solenoid replacement
- Do it yourself
- Garage job
- At a garage
- €320–650£280–570 in the UK
Transmission control module repair or replacement
- Do it yourself
- Garage job
- At a garage
- €500–1,200£430–1,050 in the UK
Complete gearbox overhaul or replacement
- Do it yourself
- Garage job
- At a garage
- €1,800–4,200£1,500–3,600 in the UK
When to go to a garage
- The car slips out of gear, revs freely without speeding up, or will not select reverse.
- The car is stuck permanently in limp mode, locked into second or third gear.
- You smell burnt transmission fluid or see large puddles of red or dark brown oil underneath the car.
- Basic code readers show only P0700 and you need a dedicated diagnostic tool to read the transmission module.
Questions drivers ask
Can I keep driving with code P0700 present?
You can usually drive a short distance at moderate speed to get home or reach a local garage. If the gearbox begins slipping, shuddering, or revving high without moving the car forward, stop immediately to avoid ruining the internal clutch bands.
Will clearing code P0700 fix my car?
No, clearing P0700 will only turn off the engine light until the transmission control module detects the issue again, which often happens within minutes. Because P0700 is an umbrella code, you must read and fix the underlying sub-code stored in the transmission computer.
How does code P0700 differ from code U0101?
Code P0700 indicates that the transmission computer is communicating normally and has actively logged a mechanical or hydraulic fault. Code U0101 means the main engine computer has completely lost electrical communication with the transmission module, usually due to broken wiring or total power loss.
Will code P0700 cause my car to fail the NCT or MOT?
On the UK MOT, an illuminated engine management light is an automatic fail for petrol cars first used from July 2003 and diesels from July 2008. On the Irish NCT, an engine light and transmission trouble codes result in an Advisory Pass on their own, but the car will fail if the fault prevents normal test completion.
Test rules here are for the National Car Test in Ireland (NCT) and the MOT in the UK. Elsewhere, check the regulations of your own country or state before going for a vehicle test.
The warning light you may see
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General guidance for most cars, not a diagnosis of yours. Details differ by make, model and year - check your handbook, and if in doubt, don't drive.