Usally it's a shift solenoid not closing or a bad clutch pack unlikely if your mileage is under 200k. Have found that this solenoid part# S9852 by BWD goes bad most of the time on Fords. It's a dual solenoid pack they are normally open flow with no power and closed when energized.
P0731 - Gear 1 Incorrect 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?
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 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.
P0731 Information for specific makes
P0731 ACURA
P0731 AUDI
P0731 BMW
P0731 CHRYSLER
P0731 DODGE
P0731 FORD
P0731 HONDA
P0731 HYUNDAI
P0731 INFINITI
P0731 JEEP
P0731 KIA
P0731 LAND-ROVER
P0731 LEXUS
P0731 MAZDA
P0731 MITSUBISHI
P0731 NISSAN
P0731 SATURN
P0731 SUBARU
P0731 SUZUKI
P0731 TOYOTA
P0731 VOLKSWAGEN
P0731 2002 NISSAN ALTIMA SEDAN
P0731 2004 NISSAN ALTIMA SEDAN
P0731 2003 NISSAN ALTIMA SEDAN
P0731 2005 NISSAN ALTIMA SEDAN
P0731 2006 NISSAN ALTIMA SEDAN
P0731 MERCEDES-BENZ
Obviously refers to auto trans , could just need the trans fluid level topping up or even changing , if this does'nt resolve the problem then a more in depth diagnosis would be required at a repair shop as could be the ECU for example but do the fluid checks and go from ther ,keep me posted
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