Possible causes

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

Tech notes

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

When is the code detected?

The TCM has detected that the transmission is trying to mechanically shift to a lower gear than intended

Symptoms

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

P0730 INFINITI 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 speed sensor (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 supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.