What it means
The transmission control module monitors the transmission mode switch C circuit voltage. It sets this code when the signal rises above the expected range, indicating an electrical high condition in that circuit.
At a glance
- Usually lights the check-engine light
How it works
Transmission mode switch C provides the transmission control module with one of the inputs used to identify the selected driving mode or selector state. P07CD sets when the voltage on switch C's circuit rises above the expected range, often because the signal is shorted to battery voltage or another powered circuit.
Common causes
Most likely first.
- Switch wire shorted to battery voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
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 scan-tool data for transmission mode switch C while selecting the available modes to see whether its state is stuck or changes incorrectly.
- Inspect the switch C connector and harness for corrosion, moisture, pushed-back pins, or wiring pinched against battery voltage or another powered wire.
- With live data displayed, gently move the switch C harness and connector to check for an intermittent high signal.
- Use the wiring diagram to test whether switch C's signal circuit is shorted to battery voltage or its supply circuit.
- If the wiring is intact, test mode switch C and the transmission control module input circuit against the manufacturer's specification.
Common fixes
- Repair a pinched or chafed wire that is feeding voltage into mode switch C's signal circuit.
- Clean and secure corroded or loose switch C connector terminals.
- Repair a damaged connector pin or loose connection at the switch or module.
- Replace the mode switch or selector assembly if its switch C output fails testing.
Can I keep driving?
If the selected mode is recognized and shifting feels normal, drive cautiously to a repair location. Avoid relying on an unconfirmed mode selection; stop if the transmission engages unexpectedly, shifts harshly, or enters limp mode.
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.