What it means
The transmission control module monitors the transmission mode switch D circuit voltage. It sets this code when the signal falls below the expected range, indicating an electrical low condition in that circuit.
At a glance
- Usually lights the check-engine light
How it works
The transmission mode switch D is an electrical input the transmission control module uses to identify a selector or drive-mode state. The module sets P07CF when the D input drops below its expected range, which can happen if its wire is grounded or the connection is poor.
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
- Save the freeze-frame data and check transmission live data for the mode switch D input to see when it reads low.
- With the vehicle safely parked, inspect the switch D wiring for chafing or insulation worn through to ground.
- Check the D-circuit connector pins for corrosion, looseness, or poor contact.
- Use the wiring diagram to test the D signal for a short to ground and check continuity between the switch and transmission control module.
- If the wiring and connections pass, test the mode switch D and module input using the manufacturer's procedure.
Common fixes
- Repair chafed D-circuit wiring that is contacting ground.
- Clean or repair corroded or loose connector terminals.
- Repair or replace the transmission mode switch if it fails testing.
- Repair the circuit or module input if tests isolate the fault there.
Can I keep driving?
Avoid long trips or heavy acceleration if shifting is harsh, delayed, or slipping; the transmission may enter a restricted gear strategy and continued slipping can cause damage. If it shifts normally, drive only as needed to reach a repair location and stop if shifting becomes unsafe.
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.