The auto box isn't achieving the commanded gear ratio.
P0730 — also written PO73O, P 0730, 0730 — is the OBD-II code for incorrect gear ratio. Same code, same fix: this page covers every spelling of it.
This code means the computer has clocked that the engine revs don't match the wheel speed for the gear you're in—basically, your automatic gearbox is slipping. It’s a common headache on high-mileage ZF 6HP boxes and those Aisin units in Volvos and Vauxhalls.
P0730 is a transmission fault code, typically costing £200–£2500 to put right in a UK garage.
What P0730 actually feels like to drive
- The car 'neutralises' or revs up between the 2nd and 3rd gear shift.
- Transmission Fault message on the dash and the car won't go over 30mph (Limp Mode).
- A violent 'thump' or jolt when coming to a stop at a junction.
- The engine revs rise like a slipping manual clutch when you try to overtake on the A9.
- Selecting 'Drive' takes 3 or 4 seconds to actually engage after moving the lever.
What causes P0730?
- Worn clutch packs
- Failed solenoid
- Low ATF
UK vehicles that throw P0730 most often
- BMW 3 Series (E90) 2005-2012 (ZF 6HP)
- Land Rover Discovery 3/4 (ZF 6-speed) 2004-2016
- Vauxhall Insignia (AF40 Aisin box) 2008-2017
- Volvo XC90 2.4 D5 2002-2014
- Jaguar XF 3.0D 2008-2015
- Ford Mondeo Mk4 (Powershift/6DCT450) 2007-2014
How P0730 is fixed
- ATF and filter service first
- Replace solenoid pack
- Full rebuild if slipping
The P0730 misdiagnosis that wastes money
I see folks constantly throwing £150 at a new speed sensor or a 'magic' bottle of transmission additive because they’re terrified of the gearbox dying. In my experience, if the fluid looks like Guinness and smells like a bonfire, the damage is already done. Most P0730s on older ZF boxes or Vauxhall units are caused by internal clutch packs that have simply disintegrated. Swapping a sensor won't fix a mechanical slip, and a cheap fluid flush can sometimes actually make the slipping worse by washing away the last bit of friction material holding it all together.
What a UK garage should charge for P0730
A basic ATF service with a new filter and high-quality fluid (like Fuchs or Liqui Moly) will run you £200-£350 at a decent indie. If it's just a solenoid pack, you're looking at £500-£800 including labour. But if the box needs a full professional rebuild with a new torque converter, you won't get much change out of £2,000 to £2,500. A main dealer won't even try to fix it; they'll just quote you £5k+ for a brand-new unit from the factory.
P0730 repair cost in the UK
Most P0730 repairs land between £200–£2500 including parts and labour. The spread is wide because the cheap fix (a sensor, a hose, a leak) and the expensive fix (a major component) throw the same code — which is why a proper diagnosis before parts are bought saves the most money.
Bob's tip on P0730
Before you let a garage quote you £2k for a rebuild, ask them to do a 'drain and fill' first—but tell them you want to see the old fluid and the magnetic pan plug. If there’s a load of 'silver glitter' or big chunks of metal in the pan, the box is a boat anchor and you’re better off looking for a low-mileage breaker unit. Also, insist they check the transmission cooler lines; on the Volvos especially, the radiator can leak coolant into the ATF (a 'strawberry milkshake' look), which kills the friction plates instantly. If that’s happened, a new box will just fail again unless you swap the radiator too.
Can you drive with P0730?
Book in — driving damages the box more.
Urgency: high.