SCP (J1850) Invalid or Missing Data for Antenna
Your vehicle's communication antenna isn't sending or receiving data properly on the J1850 network, like a radio that can't pick up the signal. The engine computer can't talk to other modules because the antenna data is corrupted or missing.
The ECU monitors the SCP (J1850) bus antenna signal for valid data frames and checksums. It detects missing packets or corrupted messages from the antenna circuit that should maintain constant communication with other vehicle modules.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| SCP Signal Validity | Valid data frames with correct checksums received continuously | Invalid, missing, or corrupted antenna data for >2 seconds |
| Antenna Circuit Voltage | Stable differential voltage within protocol specs | No signal or voltage dropout detected |
Code U1158 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, U1158 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.