P0735

What does P0735 mean?

P0735 is a Powertrain (engine, transmission, fuel system) fault code. It indicates: Gear 5 Incorrect Ratio.

This is a standardised OBD-II code. The technical definition is the same regardless of the make or model of vehicle, although specific causes and symptoms can vary between vehicles.

Symptoms commonly associated with this code

Symptoms that drivers often report alongside this code. Not all may apply to every case:

• • Engine revving high for the road speed once you're cruising on the motorway, as if it never quite found top gear
• • Harsh or delayed shift going into fifth, sometimes a flare in revs before it grabs
• • Slipping under load when it should be settled in fifth
• • Car drops into limp mode and holds a lower gear to protect itself
• • Engine warning light on, sometimes with a flashing gearbox or PRNDL display
• • Fuel economy noticeably worse on longer runs because it's sitting in the wrong ratio

Possible causes

Causes commonly associated with P0735, listed in approximate order of typical investigation. The actual cause on a specific vehicle can only be confirmed by professional diagnosis.

1. 1. Low or burnt transmission fluid, the first thing to rule out because the box runs on hydraulic pressure and dirty or low fluid kills shift quality. Often shows up on older autos that have never had a fluid service
2. 2. Worn or sticking shift solenoid for the fifth gear circuit, so the clutch pack doesn't get fed the pressure it needs at the right moment
3. 3. Valve body wear or a blocked passage in the valve body, common on higher-mileage boxes and a known weak spot on some VAG and ZF units
4. 4. Clutch pack or band wear inside the box that lets fifth slip even when commanded correctly
5. 5. Faulty input or output speed sensor feeding the TCM wrong figures, so the calculated ratio looks wrong when the gearbox is actually fine
6. 6. Corroded or damaged wiring and connectors at the solenoid pack or speed sensors, which can mimic an internal fault
7. 7. Outdated TCM software, worth checking because some manufacturers have shift logic updates that cure this

How mechanics typically diagnose

A typical diagnostic sequence used by mechanics, provided here for educational reference only. Diagnostic work should be performed by a qualified mechanic with the appropriate tools and training.

1. 1. Check the transmission fluid level and condition first, on a level surface and at the right temperature for that box. Low, dark, or burnt-smelling fluid explains a huge share of these and costs nothing to look at
2. 2. Pull all stored codes and the freeze frame data, then note any speed sensor or other ratio codes (P0730 to P0736) sitting alongside it, because they change the whole story
3. 3. Hook up a proper scan tool and watch input and output shaft speeds plus the calculated ratios on a test drive, so you can see exactly where fifth falls down
4. 4. Inspect the wiring and connectors at the solenoid pack and speed sensors for corrosion, oil contamination, and chafing
5. 5. Check for manufacturer service bulletins and TCM software updates for that specific model before you start throwing parts at it
6. 6. If fluid, wiring, sensors and software all check out, the box needs opening up to assess the valve body, solenoids, and the fifth gear clutch pack

Common questions about P0735