Ford 647 Improper gear ratio in 3rd gear

How to read it

Code 647 reads as 6 flashes, pause, 4 flashes, pause, 7 flashes on the check-engine light. Jumper the self-test input to signal return at the test connector, then run the key on engine off self test and the running self test, counting the check-engine flashes each time.

What does Ford code 647 mean?

Improper gear ratio in 3rd gear

Common causes of 647

• A 3rd gear ratio that does not match because clutch packs slip
• Low or worn fluid that lets 3rd gear slip
• A range sensor reading the wrong position in 3rd gear
• Worn or broken hard parts in the 3rd gear set

How to fix 647

1. Check the transmission fluid level and condition, and watch for slip in 3rd gear
2. Check the range sensor adjustment and the shift linkage
3. Check the connector pins and wiring for the 3rd gear shift solenoid
4. Test the range sensor and replace it only if it fails its own test
5. Test the PCM last, only after every circuit test has passed
6. Clear the code, then retest to confirm the fix holds

Source

Qualified source review