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. 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.
Medium severity. Can I keep driving?Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
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
Most likely causes
- Fluid level too low or fluid worn or contaminated
- Clutch or brake for fourth gear worn (linings, piston seal)
- Sticking shift or pressure valve, leaking valve body gasket, blocked passages
- GM manual transmissions only: gear position sensor faulty or not learned
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- Repair difficulty: hard
- It can trigger limp mode.
- It affects emissions.
What each character of P0734 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- 7: Transmission
- 34: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0734?
Drive gently to a repair shop. If it slips, you hear clunks, or it loses its gears, do not keep driving.
What causes code P0734?
The most common causes are: fluid level too low or fluid worn or contaminated; clutch or brake for fourth gear worn (linings, piston seal); sticking shift or pressure valve, leaking valve body gasket, blocked passages.
Related codes
- P0730Incorrect Gear Ratio
- P0733Gear 3 Incorrect Ratio
- P0735Gear 5 Incorrect Ratio
- P072FStuck in Gear 4
- P0766Shift Solenoid D Performance/Stuck Off
Sources
- saabwisonline.com: dtc p0734
- gsi.ext.gm.com: 2006trans7
- gsi.ext.gm.com: 2006trans9
- newtonnet.co.uk: fordobd2012
Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.