Up and Down Switch Input Circuit High
The ECU detected that the up/down switch signal is stuck at a high voltage level, like a light switch that's jammed in the 'on' position. This means the transmission can't properly read driver inputs for shifting or adjusting gears.
The ECU monitors the up/down switch voltage signal from the transmission control lever or buttons. It expects the signal to toggle between low and high states when the driver operates the switch. A continuously high signal indicates a stuck switch, wiring short, or internal circuit failure.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Switch Input Voltage | 0.5V-4.5V (toggling between states) | >4.5V (continuously high) |
| Switch State Transitions | Frequent changes with driver input | No state changes or stuck high |
Code P0828 is a moderate fault. You can generally drive to a workshop, but avoid long trips or high-load driving (motorway, uphill towing) until it is diagnosed. If the code keeps returning after clearing, or if you notice the symptoms listed above worsening, do not delay professional diagnosis. Many moderate codes have multiple possible root causes — a mechanic with live OBD data can identify the exact fault more efficiently than part-by-part trial and error.
Once the fault is repaired, P0828 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.