SCP (J1850) Invalid or Missing Data for Legislated Diagnostics
Your vehicle's computer isn't receiving required diagnostic data from the SCP communication bus, like a phone that can't get a text message. This prevents the system from monitoring emissions equipment properly.
The ECM monitors the SCP (J1850) serial communication bus for mandatory diagnostic data from modules like the transmission control, emission controls, and other systems. If expected data packets fail to arrive within specified intervals, the fault sets.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| SCP Bus Message Arrival | Data received every 10-100 ms from required modules | Missing or invalid data for >500 ms from legislated systems |
| Data Validity Check | Checksum and CRC values match expected patterns | Corrupted or mismatched data packets detected |
Code U1106 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, U1106 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.