P0730

What P0730 Means

Code P0730 indicates an incorrect gear ratio in the automatic transmission. The transmission control unit (EGS) compares the actual gear ratio, calculated from input and output shaft sensor signals, against the ratio specified for the currently engaged gear. If the discrepancy exceeds the allowable threshold, the fault is stored.

Common causes:

• worn friction discs (clutch packs);
• faulty valve body solenoids;
• problems with the valve body itself (clogged channels, worn valves).

The system relies on hydraulic pressure controlled by solenoids, which in turn receive commands from the EGS. A pressure fault or worn friction discs cause slip and a mismatch in gear ratio.

Symptoms

• Harsh shifts — most noticeable when changing from one gear to another.
• Slipping — engine rpm climbs, but speed doesn't increase proportionally.
• Transmission limp mode — the transmission locks into a fixed gear (usually 3rd or 4th) and won't shift.

Diagnosis and Repair

1. Transmission scan — read fault codes and sensor data with diagnostic equipment (ISTA, INPA).
2. Check fluid level and condition — make sure the level is correct and the fluid is clean.
3. Fluid change — replace the fluid and filter if needed.
4. Transmission repair — if worn friction discs or a faulty valve body/solenoids are confirmed, the unit needs to be disassembled and the worn components replaced.

Secondary Issues

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