What it means
The control module monitors the transmission mode switch F circuit signal. It sets this code when the signal is lower than the expected range.
At a glance
- Usually lights the check-engine light
How it works
The transmission mode switch F is an electrical input the transmission control module uses to recognize a selector or drive-mode state. P07D5 sets when the F signal falls below its expected range, indicating a low-signal fault such as a short to ground or damaged insulation.
Common causes
Most likely first.
- Switch wire shorted to ground
- Connector pins corroded - high contact resistance
- Harness chafing through insulation
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and check mode switch F live data to confirm the low reading and when it occurs.
- Inspect the F-circuit harness for chafing or worn insulation that could let the signal wire contact ground.
- Check the F connector pins for corrosion, looseness, or poor contact.
- Using the wiring diagram, test the F signal for a short to ground and verify continuity between switch and module.
- If the wiring passes, test the mode switch F and transmission control module input according to the manufacturer's procedure.
Common fixes
- Repair chafed F-circuit wiring that is touching ground.
- Clean or repair corroded or loose connector terminals.
- Replace the mode switch F if it fails its specified test.
- Repair the module input circuit if testing confirms the fault is there.
Can I keep driving?
Avoid heavy loads and long trips if the transmission slips, shifts harshly, or remains in one gear, since continued slipping can cause more damage. If shifting is normal, limit driving to a cautious trip for diagnosis.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.