SCP (J1850) Invalid or Missing Data for Odometer
Your vehicle's instrument cluster isn't receiving valid odometer data from the powertrain control module over the SCP communication bus. Think of it like a phone that can't receive text messages from one specific contact.
The ECM continuously transmits odometer distance data via the J1850 SCP (SAE J1850 Standard Corporate Protocol) serial communication bus to the instrument cluster. The cluster expects valid odometer updates at regular intervals with proper data checksums. If data is missing, corrupted, or fails validation checks for a threshold time period, this fault code sets.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| SCP Message Validity | Valid odometer data received every 100-500ms with correct checksum | Missing or invalid odometer message for >2 seconds or checksum failure |
| Data Range Check | Odometer increments logically within vehicle speed parameters | Data missing entirely or implausible values detected |
Code U1122 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, U1122 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.