U0647 code meaning
Lost Communication With Motor Electronics Coolant Pump B
Network system Generic code U06xx codes Check engine light
What U0647 means
Cars fitted with two or more drive units, or with separate loops for the motor and its inverter, may fit a second networked pump in the motor electronics circuit, called B. U0647 is logged when this pump no longer returns its status frames. Public manufacturer documentation for U0647 does not exist. Since it is a separate node, the typical clue is that pump A and the rest of the bus still communicate, which narrows the search to pump B's own branch of wiring, its connector and its fuse. The conventional circuit codes for this pump are P0B38 to P0B3A, with P0C74 for performance and P2D05 to P2D09 for internal pump faults. Electric pumps such as Bosch's PCE generation take LIN commands and diagnose themselves. Expect reduced power from the axle that pump B cools.
U0647 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyMedium
- Typical labor0.5 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0647
- Hybrid or EV warning lamp, MIL on hybrids
- Power limited on one drive unit
Common causes of U0647
- Most likelyWiring branch or fuse that serves only pump B open
- PossiblePump B connector corroded or not fully seated
- PossiblePump B electronics failed
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Motor electronics coolant pump bVehicle bus wiring
What each part of U0647 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 47 | The exact fault in that area. |
What to do next
- Note U0647 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 U0647
What does U0647 mean?
U0647 means "Lost Communication With Motor Electronics Coolant Pump B". Cars fitted with two or more drive units, or with separate loops for the motor and its inverter, may fit a second networked pump in the motor electronics circuit, called B. It is a generic code, so it means the same on every make.
Is it safe to drive with U0647?
Drive gently and only to a workshop. With U0647 the car can go into limp mode (reduced power) to protect itself.
Will U0647 fail an emissions test?
Yes, it can. U0647 is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is U0647 to fix?
Difficulty: medium. A typical repair takes 0.5 to 2.5 hours of work. This is a job for a workshop.
Will U0647 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.