U0649 code meaning
Lost Communication With Coolant Pump D
Network system Generic code U06xx codes Check engine light
What U0649 means
Coolant pump D is the fourth auxiliary electric pump in the generic lettering that runs from A (U0623) through B and C (U0624, U062F) to E (U0698). What D circulates is up to the manufacturer; GM, for example, assigns C to its low-temperature loop, while Mercedes uses the E code for a pump of its low-temperature circuit. U0649 is set when pump D, controlled over LIN or a similar link, no longer sends a response. No manufacturer documents U0649 publicly. Pumps of this kind receive speed commands over LIN or PWM and report their own diagnosis, as Bosch describes for the PDE. Its circuit and internal faults are P2B66 to P2B6C, with P2C49 and P2BA1 for performance and underspeed. Loss of the pump leaves its loop without circulation.
U0649 at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium
- Typical labor0.3 to 2.5 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U0649
- Warning lamp, depending on manufacturer the MIL
- Components on the affected loop run warmer than normal
Common causes of U0649
- Most likelyLIN, supply or ground wire to pump D damaged
- PossibleCorroded pump D connector
- PossiblePump D electronics failed
- Less likelyController acting as LIN master faulty or needing a software update
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Coolant pump dVehicle bus wiring
What each part of U0649 means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 49 | The exact fault in that area. |
What to do next
- Note U0649 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 U0649
What does U0649 mean?
U0649 means "Lost Communication With Coolant Pump D". Coolant pump D is the fourth auxiliary electric pump in the generic lettering that runs from A (U0623) through B and C (U0624, U062F) to E (U0698). It is a generic code, so it means the same on every make.
Is it safe to drive with U0649?
Usually yes, for a short time, if the check engine light is steady and the car drives normally. If the light flashes or the car runs badly, stop and have it checked.
Will U0649 fail an emissions test?
Yes, it can. U0649 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 U0649 to fix?
Difficulty: medium. A typical repair takes 0.3 to 2.5 hours of work. This is a job for a workshop.
Will U0649 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.