OBD-II code U0071 indicates that the vehicle's communication network, specifically designated as Bus E, is experiencing a high voltage condition. This usually means there is a short to power on the data line, which prevents the modules on that specific network from exchanging information properly.
A chafed or damaged wire in the Bus E circuit touching a power source is the most common cause, pulling the network voltage high.
A module on Bus E has internally shorted to power, which bleeds voltage onto the communication line and disrupts the network.
Corrosion or bent terminals in a network connector can bridge the data line to a power pin, causing a high voltage condition.
An improperly installed aftermarket device, such as a remote starter or alarm, may be back-feeding voltage into the communication bus.
An internal failure in the Powertrain Control Module is extremely rare and should only be considered after all wiring and other modules are ruled out.
It means the communication line designated as 'Bus E' is shorted to a power source. This keeps the voltage on the data line 'high' when it should be fluctuating, preventing the computers from reading the data.
Rarely. Mechanics frequently misdiagnose this as a bad PCM, but the control module is almost never the cause. The code is overwhelmingly caused by wiring shorts or a failure in a different module on the Bus E network.
It is not recommended. A disrupted communication network can cause unpredictable vehicle behavior, including the loss of critical safety functions, erratic gauge readings, or stalling.
When Bus E fails, every module that relies on that network loses communication and sets its own loss-of-communication code. These are usually secondary codes that clear up once the primary Bus E short is repaired.