Transmission

P0730 — Incorrect Transmission Gear Ratio

Severity: high Drive with care, to a shop

What P0730 means

The transmission control module compares input shaft speed with output shaft speed to calculate the current gear ratio. If the result doesn't match what is expected for the selected gear, it stores P0730. This usually points to clutch slip, low hydraulic pressure, a faulty solenoid or a bad speed sensor.

Symptoms

  • Check Engine or transmission warning light is on
  • Delayed, harsh or incorrect shifts
  • Engine revs rise without matching acceleration (slipping)
  • RPM flare between gears
  • Limp mode limiting gear selection
  • Burning smell from the transmission
  • Worse fuel economy

Possible causes

  1. Low, burnt or contaminated transmission fluid
  2. Faulty shift solenoids
  3. Failed input or output speed sensors
  4. Worn clutch packs or other internal parts
  5. Worn valve body causing low line pressure
  6. Damaged wiring or corroded connectors
  7. TCM software or internal fault

How to diagnose

  1. Scan all codes and freeze frame data, looking for other transmission or engine codes
  2. Check fluid level, color and smell following the manufacturer's procedure
  3. Inspect transmission wiring and connectors for damage, fluid and corrosion
  4. Compare input and output speed sensor readings on a scan tool with actual vehicle speed
  5. Test solenoid operation and line pressure
  6. Look for service bulletins and TCM software updates
  7. If the fluid has metal debris, drop the pan and inspect for wear

Common fixes

  • Change the fluid and filter and correct the fluid level
  • Replace faulty solenoids or speed sensors
  • Repair wiring and connectors, and fix ground faults
  • Reflash or replace the TCM
  • Repair or rebuild the transmission (clutches, valve body)

Questions and answers

Can I drive with a P0730 code?

Only briefly and gently to get to a shop. Slipping overheats the transmission and can destroy it quickly, so don't put off diagnosis.

Will a fluid change fix P0730?

Sometimes, if low or dirty fluid is the cause. If the clutches are worn or a solenoid has failed, fresh fluid won't help and the code will return.

Can I just clear the P0730 code?

You can, but it will come back if the cause remains. Check the fluid, wiring and sensor data first.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.