Vehicle Communication Bus E (-) High
What it means
U0071 means the CAN-Low (-) line of communication bus E is reading abnormally high voltage, usually from a short to a power feed or across to CAN-High, or a module driving the line high. Bus "E" is defined by the manufacturer, so the effect depends on which network it is — most often lost features and warning lights. Scanning all modules reveals which dropped off and points to the wiring short or failed module behind it.
Can I keep driving? Often drivable, but expect warning lights and lost features on bus E; scan to confirm which network is affected before relying on the car.
Common symptoms
What you'll notice
- Multiple modules on bus E reporting communication faults
- Warning lights and dead or erratic features
- Several codes set at once
- Intermittent faults that track with wiring movement or moisture
Common causes
Most likely first
- CAN-Low (-) wire shorted to a power feed, pulling the line highLikely
- CAN-Low shorted to CAN-HighCommon
- Corroded or damaged connector on the bus E circuitCommon
- A failed module driving the bus voltage highLess often
How to diagnose & fix
Work through it in order
- Scan all modules and record the codes to identify the affected segment of bus E.
- Back-probe CAN-High and CAN-Low and compare voltages to spec to confirm the high-side fault.
- Inspect the bus E wiring for shorts to power or across the pair, and check connectors for corrosion.
- Disconnect suspect modules one at a time to see if the bus normalizes, isolating a failed module.
- Repair the wiring short or replace the faulty module, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with U0071?+
Can I just clear U0071?+
Related codes
Often seen with U0071
Read & clear U0071 yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.