SCP (J1850) Invalid or Missing Data for Primary Id
Your vehicle's modules aren't communicating properly over the J1850 network bus—think of it like a phone line between computers going dead. The primary module isn't sending or receiving required data packets.
The ECU monitors incoming J1850 serial data frames from the primary control module at regular intervals. It validates message structure, timing, and checksums to ensure data integrity. If expected messages don't arrive within threshold windows or contain invalid data, the fault sets.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Message Arrival Interval | 10-50ms per frame | No valid frame received for >100ms |
| Data Checksum Validation | Checksum matches calculated value | Checksum mismatch or missing data bytes |
Code U1047 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, U1047 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.