SCP (J1850) Invalid or Missing Data for Primary Id
Your vehicle's main computer isn't receiving proper data from the body control network—like a driver not hearing radio instructions clearly. The SCP bus (a communication network) is either missing data or sending corrupted messages for a critical module.
The ECM monitors the SCP (J1850) serial communication bus for valid data packets from the primary module ID. When expected messages don't arrive within a specific time window or contain invalid checksums, a fault is logged. The bus operates at a fixed baud rate and requires proper voltage levels and termination.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| SCP Bus Message Reception | Valid packets received every 10-50ms with correct checksum | Missing packets or invalid data for >500ms |
| SCP Bus Voltage | 0-5V differential signal with clean edges | Corrupted signal, open circuit, or short to ground |
Code U1063 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, U1063 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.