P0731 KIA First Gear Incorrect Ratio

Possible causes

– Low transmission fluid level
– Dirty transmission fluid
– Shift solenoids
– Transmission mechanical problems
– Transmission hydraulic control circuit

Tech description

Start by inspecting the transmission fluid level and condition, and change fluid if necessary.

When is the obd code mean?

P0731 is detected when A/T cannot be shifted to the 1st gear position even if electrical circuit is good.

Symptoms

– Engine Light ON (or Service Engine Soon Warning Light)
– Incorrect transmission shifting

P0731 KIA OBD Code Description

This diagnosis monitors actual gear position by checking the torque converter slip ratio calculated by Transmission Control Module (TCM) as follows:

Torque converter slip ratio = A x C/B

A: Output shaft revolution signal from revolution sensor

B: Engine speed signal from Engine Control Module (ECM)

C: Gear ratio determined as gear position which TCM supposes

If the actual gear position is higher than the position (1st) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.