Park Switch Indicates Park with Vehicle Moving
Your vehicle's park switch is telling the computer the car is in Park, but the vehicle is actually moving. Think of it like a door sensor that says the door is closed while you're driving with it open.
The ECM monitors the park switch signal from the transmission to verify Park mode status. It cross-references this signal against vehicle speed data from the wheel speed sensors. If the park switch reads active while speed exceeds the threshold, a fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Park Switch Signal vs Vehicle Speed | Park switch active only when vehicle speed = 0 mph | Park switch active when vehicle speed > 2-5 mph |
| Park Switch Voltage | 0.5-2.0V (inactive) or 4.5-5.0V (active) | Voltage inconsistent with actual gear position |
Code C1945 is classified as a serious fault. If your check engine light is flashing — not just steady — pull over safely and do not continue driving. A flashing CEL indicates an active misfire or critical failure that can cause catalytic converter damage within minutes or permanent engine harm within miles. Contact a certified mechanic immediately. Do not attempt roadside repairs on high-severity codes unless you are trained to do so.
Once the fault is repaired, C1945 can be cleared using any OBD-II scanner. Connect the scanner, navigate to "Clear Codes" or "Erase DTCs," and confirm. The check engine light turns off immediately.
The code will return if the root cause was not actually fixed. The ECM re-detects the fault within 1–3 drive cycles and sets the code again.