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?

Transmission in fourth gear and the ECM detected an incorrect gear ration

Symptoms

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

P0734 FORD 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 (4th) supposed by TCM, the slip ratio will be more than normal. In case the ratio exceeds the specified value, TCM judges this diagnosis malfunction.

FORD Technical Service Bulletins for P0734 code