What it means
The upshift and downshift switch signals do not correlate with the transmission range signal as expected.
At a glance
- Usually lights the check-engine light
How it works
The upshift and downshift switch lets the driver request a gear change, while the transmission range signal tells the controller the selected range. P0819 sets when those inputs do not agree in the way the control system expects, such as when a switch remains active or the signals are crossed after service.
Common causes
Most likely first.
- Stuck paddle/button input
- Swapped wiring after service
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 freeze-frame data and read transmission codes to determine whether the correlation fault appeared during a shift request or after recent work.
- Use scan-tool live data to watch the upshift, downshift, and transmission range signals while operating the selector and shift buttons or paddles.
- Check that each button or paddle returns to its inactive state when released and that the displayed range matches the selector position.
- Inspect the shift-switch and range-signal connectors and harness, paying particular attention to wiring recently disturbed during service.
- If the signals remain mismatched, test the switch and wiring against the vehicle's diagram to find a stuck input, swapped connection, or circuit fault.
Common fixes
- Free or replace a shift button or paddle that sticks.
- Correct crossed or swapped wiring introduced during service.
- Repair a damaged connector or wire affecting the switch or range signal.
- Replace a failed shift switch after confirming it does not change state correctly.
Can I keep driving?
The transmission may ignore manual upshift or downshift requests or shift unpredictably. Avoid relying on manual gear selection; if the selected range is uncertain or shifting becomes unsafe, stop driving and have the fault checked.
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.