What P0734 means
The transmission module divides input (turbine) speed by output speed and compares the result with the ratio of the commanded gear; a deviation means slip – a clutch or brake not holding, too little pressure – or a wrong gear.
How the engine computer detects it
Thresholds: Ford more than 30 rpm off for 1.8 s three times (diesel 2023: over 20 % for 12 s), GM's 2006 tables and the Allison 1000 converter slip of 200–230 rpm for 2.25 s after one trip, Saab's Aisin boxes over 20 % twelve times without MIL. P0734 concerns fourth gear. A 2006 GM table separates it explicitly from P0730: fourth gear showing the ratio of third is P0730, any other deviation P0734. Slip shows as raised engine speed or no upshift into fourth. On GM manual transmissions it checks the gear position sensor.
Written from public technical sources and not yet checked by a mechanic. How we write these pages
Symptoms
- Slipping or flare in fourth gear, engine speed higher than expected
- Harsh or delayed shifts
- Limp mode (Aisin: second gear and reverse only), transmission warning
- Check engine light depending on manufacturer
Common causes
- Fluid level too low or fluid worn or contaminated Most likely
- Clutch or brake for fourth gear worn (linings, piston seal) Most likely
- Sticking shift or pressure valve, leaking valve body gasket, blocked passages Possible
- GM manual transmissions only: gear position sensor faulty or not learned Possible
How to diagnose P0734
- Read every stored code with an OBD-II scanner. If misfire or fuel trim codes are there too, fix those first: they often cause this one.
- Inspect the parts involved: transmission clutches, transmission valve body, transmission fluid, transmission control module.
- Work through the causes above from most to least likely, cheapest checks first.
- Clear the code and drive a full drive cycle to confirm the repair held.
Vehicles that report P0734 most
| Vehicle | Years | Reports | Share | Median miles |
|---|---|---|---|---|
| Ford F-150 | 2017–2020 | 9 | — | |
| Chrysler Town and Country | 2011–2016 | 3 | — |
Counts of owner complaints to the NHTSA that mention P0734 (29 in total), not failure rates: popular models get more complaints simply because more of them are on the road. Models with fewer than 3 complaints are left out.
Reading the code
- P
- Powertrain
- 0
- Generic (SAE) code
- 7
- Transmission
- 34
- Specific fault
Questions drivers ask
Can I drive with code P0734?
If the car shifts normally, drive gently to a shop. If it's stuck in one gear, slips, shifts harshly or won't move out of Park, don't drive it: have it towed.
Will my car pass an emissions inspection with P0734?
Probably not in states that test vehicles with an OBD-II scan: an emissions-related code that keeps the check engine light on is usually an automatic fail. Rules differ by state and county, so check yours.
Often reported together
Codes that owners mention in the same NHTSA complaints as P0734. They can point to a shared cause, so it's worth checking them together.
This page is general information, not a substitute for a professional diagnosis. Repair costs are rough estimates for parts and labor and vary by vehicle and region.