SCP (J1850) Invalid or Missing Data for Throttle
The engine computer isn't receiving proper throttle position data over the SCP communication bus, like a radio station going silent. This breaks the vehicle's ability to control fuel and spark timing correctly.
The ECM monitors throttle position voltage and SCP bus messages from the throttle body sensor. It expects valid data frames at regular intervals; missing or corrupted messages trigger this fault. The throttle signal should correlate with pedal input and engine load.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| Throttle Position Voltage | 0.5V–4.5V proportional to pedal position | Out of range, missing, or no SCP message |
| SCP Bus Message Rate | Valid frames every 10–20ms | Timeout or corrupted data detected |
Code U1018 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, U1018 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.