Cause
Damaged data bus wiring
The twisted pair modules use to talk to each other. One damaged bus takes out communication with many modules at once, so a scan tool listing a dozen lost-communication codes is usually describing one fault rather than a dozen.
There is a free test: with the ignition off, the pair should read about sixty ohms — the two terminating resistors in parallel. A hundred and twenty means one end is missing, an open reading means a broken wire, and near zero means the two are shorted together.
Typically a moderate job.
Some of these codes mean you should stop driving
21 of the 415 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 (415)
Codes where this is a likely explanation first, rather than merely a possible one.
- P0728 Engine Speed Input Circuit Intermittent Likely for this code High
- P0856 Traction Control Input Signal Likely for this code Moderate
- P0860 Gear Shift Control Module A Communication Circuit Likely for this code High
- P0861 Gear Shift Control Module A Communication Circuit Low Likely for this code High
- P0863 Transmission Control Module Communication Circuit Likely for this code High
- P0864 Transmission Control Module Communication Circuit Range/Performance Likely for this code High
- P0865 Transmission Control Module Communication Circuit Low Likely for this code High
- U0001 High Speed CAN Communication Bus Likely for this code Stop driving High
- U0003 High Speed CAN Communication Bus (+) Open Likely for this code Stop driving 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
- U0006 High Speed CAN Communication Bus (-) Open 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
- U0009 High Speed CAN Communication Bus (-) Shorted to Bus (+) Likely for this code Stop driving High
- U0010 Medium Speed CAN Communication Bus Likely for this code Moderate
- U0011 Medium Speed CAN Communication Bus Performance Likely for this code Moderate
- U0012 Medium Speed CAN Communication Bus (+) Open Likely for this code Moderate
- U0013 Medium Speed CAN Communication Bus (+) Low Likely for this code Moderate
- U0014 Medium Speed CAN Communication Bus (+) High Likely for this code Moderate
- U0015 Medium Speed CAN Communication Bus (-) Open Likely for this code Moderate
- U0016 Medium Speed CAN Communication Bus (-) Low Likely for this code Moderate
- U0017 Medium Speed CAN Communication Bus (-) High Likely for this code Moderate
- U0018 Medium Speed CAN Communication Bus (-) Shorted to Bus (+) Likely for this code Moderate
- U0019 Low Speed CAN Communication Bus 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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