SCP (J1850) Invalid or Missing Data for Tires
Your vehicle's tire pressure monitoring system isn't communicating properly with the engine computer over the data network. Think of it like a walkie-talkie where one person stopped transmitting their message.
The ECM monitors incoming tire pressure data via the J1850 SCP (Standardized Corporate Protocol) bus from the TPMS module. It expects valid pressure readings and sensor identification within a defined time interval. When data is missing, corrupted, or fails validation checks, the ECU logs this fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| TPMS Data Message Frequency | Valid message received every 60-120 seconds | No valid message or timeout exceeds threshold |
| Tire Pressure Value Range | 15-35 PSI per sensor | Out-of-range, missing, or corrupted data from any sensor |
Code U1229 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, U1229 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.