SCP (J1850) Invalid or Missing Data for Tires
Your vehicle's computer isn't receiving tire pressure or sensor data properly through the J1850 communication network. Think of it like a phone with no signal—the message about your tire condition isn't getting through to the dashboard.
The ECU monitors the J1850 serial data bus for tire pressure sensor (TPMS) messages from each wheel's sensor. It expects valid pressure values within acceptable ranges and proper message formatting at regular intervals. If the data is corrupted, missing, or fails parity checks, the fault is triggered.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| TPMS Signal Valid | All four sensors reporting 20-65 PSI with valid checksums | Missing data, corrupted frames, or invalid checksums for >2 seconds |
| J1850 Bus Communication | Valid CRC and message format at 10.4 kbaud | Parity errors, timeout, or bus noise detected |
Code U1228 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, U1228 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.