Cause
Poor wiring splice in an aftermarket installation
Something was added to the vehicle and connected by cutting into its wiring rather than through a designed interface — a tracker, a dashcam, an insurance box, a towing loom, a stereo, a light bar, a fleet terminal, a converter's body equipment.
The join itself is the fault, and there are only a few ways it goes wrong. A twisted-and-taped connection that corrodes and turns intermittent. A vampire tap that pierces the insulation and severs strands. A signal taken from a data bus pair, which is a matched, terminated transmission line rather than a wire — anything hung on it changes its electrical characteristics and can corrupt messages for every module on it, not just the one nearby. An earth made to painted metal or to a different point from the module it serves, creating a voltage difference where the design assumed none.
Two consequences recur, and neither is obvious from the installation. A device that keeps reading the network when the vehicle is parked stops the vehicle sleeping, and flattens the battery over a few days — normally answered with a new battery and then a new alternator. And a splice near safety-system wiring is a serious matter, because tow bar looms and audio installations are routinely run through the areas restraints sensors and their harnesses occupy.
So the question that finds this is not "what is broken" but "what has been added". It is worth asking about work a previous owner had done, and about anything that seemed too cheap for the job. The proper repair is to remove the splice and reconnect through the vehicle's own interface, which usually exists and was skipped because it costs more.
Typically a moderate job.
Some of these codes mean you should stop driving
8 of the 114 codes this can cause indicate a fault where continuing to drive risks damage or is unsafe. Which one you have matters more than the cause does — read the code's own page before deciding.
Codes this can cause (114)
Codes where this is a likely explanation first, rather than merely a possible one.
- U0001 High Speed CAN Communication Bus Likely for this code Stop driving High
- U0002 High Speed CAN Communication Bus Performance Likely for this code High
- U0004 High Speed CAN Communication Bus (+) Low Likely for this code Stop driving High
- U0005 High Speed CAN Communication Bus (+) High Likely for this code Stop driving High
- U0007 High Speed CAN Communication Bus (-) Low Likely for this code Stop driving High
- U0008 High Speed CAN Communication Bus (-) High Likely for this code Stop driving High
- U0011 Medium Speed CAN Communication Bus Performance Likely for this code Moderate
- U0014 Medium Speed CAN Communication Bus (+) High Likely for this code Moderate
- U0017 Medium Speed CAN Communication Bus (-) High Likely for this code Moderate
- U0020 Low Speed CAN Communication Bus Performance Likely for this code Moderate
- U0023 Low Speed CAN Communication Bus (+) High Likely for this code Moderate
- U0026 Low Speed CAN Communication Bus (-) High Likely for this code Moderate
- U0029 Vehicle Communication Bus A Performance Likely for this code Moderate
- U0031 Vehicle Communication Bus A (+) Low Likely for this code High
- U0032 Vehicle Communication Bus A (+) High Likely for this code High
- U0034 Vehicle Communication Bus A (-) Low Likely for this code High
- U0035 Vehicle Communication Bus A (-) High Likely for this code High
- U0037 Vehicle Communication Bus B Likely for this code High
- U0038 Vehicle Communication Bus B Performance Likely for this code Moderate
- U0040 Vehicle Communication Bus B (+) Low Likely for this code High
- U0041 Vehicle Communication Bus B (+) High Likely for this code High
- U0043 Vehicle Communication Bus B (-) Low Likely for this code High
- U0044 Vehicle Communication Bus B (-) High Likely for this code High
- U0046 Vehicle Communication Bus C Likely for this code Moderate
- U0047 Vehicle Communication Bus C Performance Likely for this code Moderate
Information, not instruction
CarGeek is a reference, not a service manual. Its pages are written from public sources and from what other people have found, never from a manufacturer's own service information, so they can be wrong or incomplete for your particular vehicle. Some of what they describe carries real risk: high voltage, fuel under pressure, stored energy, hot and moving parts.
Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
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