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OBD Trouble Code P0730 Incorrect Gear Ratio -

My check engine light is on code due to trouble code 0730 - Incorrect Gear Ratio. This is an automatic transmission. Will this keep me from passing the smog test?


OBD-II P0730 Trouble Code - Incorrect Gear Ratio

OBD-II Trouble Code P0730 refers to an Transmission Incorrect Gear Ratio

Here is what a P0730 means, in simple terms

An automatic transmission is designed to configure an optimal torque and power combination in order to provide the driver with desired speed and rate of acceleration. The system is being constantly monitored by the transmission control module (TCM). If the TCM notices a RPM difference between the transmission output sensor and input RPM sensor that is greater than a predetermined value, the TCM triggers a P0730 trouble code.

What caused my vehicle to set a P0730 trouble code?

A P0730 can be triggered while shifting between gears or when driving at a steady speed in any gear the transmission is designed to utilize. P0730 is usually triggered when there is a problem during shifting gears. Being it a generic trouble code, P0730 does not necessarily pinpoint any specific gear ratio failure. In other words, the trouble code does not indicate which one of your vehicle's gear(s) is failing. Instead, it simply advises that there is a problem between the transmission's expected output and input RPMs. Other related codes include related to the P0730 include: P0729, P0731, P0732, P0733, P0734, P0735 and P0736. These should be fixed first before fixing the incorrect gear ratio problem. More than likely the issue causing the P0730 will be resolved during the correction of the prior codes.

Here are some common faults which may cause a P0730 to be stored with the engine computer system:

  • Low or dirty transmission fluid (check this first)
  • Worn pump or clogged transmission fluid filter
  • Torque converter clutch defect
  • Internal mechanical failure
  • Faulty shift solenoid and/or wiring
  • Faulty transmission speed sensor and/or wiring
  • Faulty transmission control module

What symptoms will my vehicle experience when trouble code P0730 is set?

  • Your vehicle's check engine light (CEL), Malfunction Indicator Lamp (MIL) or Service Engine Soon light will be illuminated and freeze frame data stored with information regarding engine sensor data at the time when the incorrect gear ratio was detected by the TCM. Trouble code P0730 will also be recorded in the ECC ROM memory.
  • Bad fuel economy.
  • Unable to drive at high speed.
  • Transmission not shifting to low/high gears.

How can I fix a P0730 problem and where should I start?

We first recommend pulling the trouble code(s) from the ECC, along with the freeze frame data. The freeze frame data will give you information on the engine's exact operating condition at the precise moment the trouble code was triggered. Write down or record this information somewhere. Next, clear the ECC and drive your vehicle for at least 200 miles or until the check engine light turns on again. Try and re-create the engine condition using the freeze frame data. If the check engine light returns, extract the trouble codes and verify that trouble code P0730 is still present.

If so, move on to inspecting the transmission fuse(s). Ensure none are defective. Next move on to checking the wiring harness and wiring connections to the transmission for damaged. If the wiring to the transmission control module and torque converter clutch solenoid are not damaged, your next step would be to test the TCC solenoid itself, as well as verify the TCM is commanding the solenoid on (power at solenoid when activated by TCM). This diagnosis is a bit more complicated and may require an experienced technician. Possible fixes to clear a OBD-II Trouble Code P0730 include:
  • Inspect electrical connections and wires connecting sensors to the transmission control module.
  • Repair or replace any damaged wires in and around the transmission control module.
  • Repair or replace any damaged wires in and around transmission speed sensor.
  • If transmission fluid filled to proper level and transmission sensor and solenoid wiring in working condition, components within the transmission may need to be repaired or replaced.

Can I drive my vehicle with a P0730 trouble code and illuminated CEL?

  • You may drive your vehicle with a P0730 however keep in mind your vehicle will not pass a smog inspection.
  • Problems with the incorrect gear selection may cause drive-ability symptoms.
  • The check engine light or malfunction indicator lamp will be illuminated as long as a P0730 is recorded in the ECC.

posted by SmogTips Support

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