Lost Communication With Head Up Display
Your vehicle's main computer lost contact with the head-up display unit, like a phone losing connection to a Bluetooth speaker. The display won't function until the communication link is restored.
The ECU continuously monitors serial communication signals to the HUD module via CAN bus or dedicated data line. It detects missing acknowledgment frames or timeouts when trying to send display commands. If the ECU doesn't receive expected response signals within a set time window, it logs this communication fault.
| Parameter | Normal Range | Fault Condition |
|---|---|---|
| CAN Bus Message Timeout | HUD responds within 100-200ms | No response after 3+ consecutive message attempts |
| Signal Voltage Level | 5V±0.5V on communication line | Below 2V or above 5.5V indicating open/short circuit |
Code U0158 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, U0158 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.