U0045 code meaning
Vehicle Communication Bus B (-) Shorted to Bus B (+)
What U0045 means
U0045 describes the two wires of Vehicle Communication Bus B touching each other. Deutz uses this code in the EMR L1 engine controller for a short circuit on its third CAN channel, without further detail. On a high-speed-type CAN, bridged wires leave no differential voltage, every bit reads recessive and, per onsemi, nothing can be transmitted while the CANH driver works into its current limit; NXP adds that transceiver diagnosis cannot see this short. On a fault-tolerant low-speed network, NXP's TJA1055 first sees a permanent dominant level, then after a time-out switches off CAN-Low and keeps going on CAN-High. Typical causes are crushed harness sections, water in splices and a damaged module input. No car maker documents U0045 publicly; near-zero ohms between the wires with the battery off confirms the fault.
U0045 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modePossible
- Repair difficultyHard
- Typical labor1 to 6 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0045
- Every function on Bus B unavailable (high-speed type)
- Several warning lamps on at once
- Lost-communication codes in modules on other networks
Common causes of U0045
- Most likelyHarness crushed so that both bus wires touch
- PossibleWater in a splice or connector bridging the two wires
- Less likelyDamaged module input shorting its bus pins
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Bus b wiring
What each part of U0045 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 45 | The exact fault in that area. |
What to do next
- Note U0045 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about U0045
What does U0045 mean?
U0045 means "Vehicle Communication Bus B (-) Shorted to Bus B (+)". U0045 describes the two wires of Vehicle Communication Bus B touching each other. It is a generic code, so it means the same on every make.
Is it safe to drive with U0045?
Drive gently and only to a workshop. With U0045 the car can go into limp mode (reduced power) to protect itself.
Will U0045 fail an emissions test?
U0045 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is U0045 to fix?
Difficulty: hard. A typical repair takes 1 to 6 hours of work. This is a job for a workshop.
Will U0045 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.