P0731 FORD Incorrect First Gear Ratio

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 first gear and the ECM detected an incorrect gear ration
Symptoms
– Engine Light ON (or Service Engine Soon Warning Light)
– Incorrect transmission shifting
P0731 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 (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.

FORD Technical Service Bulletins for P0731 code
1996 FORD CONTOUR POWER TRAIN:AXLE ASSEMBLY
1996 FORD PROBE POWER TRAIN:AXLE ASSEMBLY
1997 FORD CONTOUR POWER TRAIN:AXLE ASSEMBLY
1997 FORD PROBE POWER TRAIN:AXLE ASSEMBLY
1998 FORD CONTOUR POWER TRAIN:AXLE ASSEMBLY
1999 FORD CONTOUR POWER TRAIN:AXLE ASSEMBLY
2000 FORD CONTOUR POWER TRAIN:AXLE ASSEMBLY
2001 FORD ESCAPE POWER TRAIN:AXLE ASSEMBLY
2002 FORD ESCAPE POWER TRAIN:AXLE ASSEMBLY