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GTECH Calibration
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P0730

Incorrect Gear Ratio.

  • Generic
  • Powertrain
  • Generic code
  • High severity

How this code is built

P
SystemPowertrain
0
Defined bySAE, the same on every car
7
AreaTransmission
30
FaultThe specific fault in that area

What it means

P0730 is the generic code for an incorrect gear ratio. The transmission control unit compares input shaft speed with output shaft speed (and engine speed) and calculates the actual ratio. If that ratio does not match the gear it has commanded, beyond a set tolerance for a set time, it logs the code. It points to slip or a mismatch in the transmission, but the exact cause depends on the transmission type and model.

Symptoms

  • Engine revs rise without matching acceleration (slipping)
  • Harsh, delayed or flared gear changes
  • Transmission stuck in one gear or in limp mode
  • Gearbox warning light or malfunction indicator lamp on
  • Poor acceleration or reduced top speed
  • Burning smell from hot transmission fluid

Possible causes

  • Low, degraded or contaminated transmission fluid causing clutch slip or low hydraulic pressurelikely
  • Faulty shift solenoid or pressure control solenoid sticking or not respondinglikely
  • Faulty input or output shaft speed sensor, or wiring and connector fault giving an incorrect speed signalpossible
  • Worn clutches or bands inside the transmissionpossible
  • Valve body wear, blocked passages or internal hydraulic leakspossible
  • Torque converter fault, such as clutch slip or failure to lock correctlypossible
  • Faulty transmission control unit or an outdated calibration known for this fault on certain modelsrare

How to diagnose

  1. Read all stored codes and freeze frame data, noting gear commanded, speeds, fluid temperature and load when the fault set
  2. Check for related codes such as speed sensor, solenoid or shift circuit faults and deal with those first
  3. Check transmission fluid level, condition and smell using the correct procedure for the model, as some are sealed units that need a set fluid temperature
  4. Inspect wiring and connectors at the transmission for damage, chafing, fluid ingress or corrosion
  5. Compare live input, output and engine speed data and check the calculated ratio in each gear
  6. Test solenoid circuits and resistance against the manufacturer's specification
  7. Check for software updates or technical bulletins for the specific model and transmission
  8. Carry out pressure and stall tests where the manufacturer specifies, to separate hydraulic from mechanical faults

How to fix

  • Correct the fluid level and change degraded fluid and filter with the specified type, if the model allows
  • Repair or replace damaged wiring, connectors or faulty speed sensors
  • Replace faulty shift or pressure solenoids
  • Repair or replace the valve body if worn or blocked
  • Overhaul or replace the transmission or torque converter if internal wear is confirmed
  • Update the transmission control unit calibration only where a bulletin confirms it addresses this fault

Can I keep driving?

High severity

Avoid driving if the transmission is slipping or in limp mode, as continued use can quickly cause expensive internal damage. If it is only an occasional fault, keep journeys short and gentle and have it checked as soon as possible.

Guide written by AI from the code's definition. Confirm with a diagnosis before replacing parts.

This code for other makes

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