U013D code meaning
Lost Communication With Vacuum Sensor A
Network system Generic code U01xx codes Check engine light
What U013D means
U013D stands for lost communication with vacuum sensor A, a networked sensor that reports the vacuum in the brake booster or a vacuum reservoir. Engines with little manifold vacuum, such as turbocharged direct-injection units, and hybrids use this value to switch on an electric vacuum pump or to throttle the engine so the brake assist stays sufficient. No manufacturer documents U013D in public; GM's 2019 ECM tables show the analog form of this sensor with codes P0556 to P0558, classified as Type B. CARB demands a separate code for lost communication of digital inputs. Sensor B uses U013E, invalid data from sensor A U043E. Possible effects: brake assist warning, start-stop disabled, MIL depending on the manufacturer.
U013D at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modeNot expected
- Repair difficultyMedium, DIY possible
- Typical labor0.5 to 2 hours
- Clears after repairWhen cleared with a scanner
Symptoms of U013D
- Brake booster or brake assist warning
- Electric vacuum pump runs constantly or start-stop disabled
- MIL on depending on the manufacturer
Common causes of U013D
- Most likelyLoose or corroded connector at the vacuum sensor on the booster
- PossibleSupply, ground or bus wiring of the sensor faulty
- Less likelyVacuum sensor A internally faulty
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Vacuum sensor aCAN bus wiring
What each part of U013D means
| U | Network system: communication between the control modules (CAN bus). |
| 0 | Generic code: it means the same on every make (SAE standard). |
| 3D | The exact fault in that area. |
What to do next
- Note U013D 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 U013D
What does U013D mean?
U013D means "Lost Communication With Vacuum Sensor A". U013D stands for lost communication with vacuum sensor A, a networked sensor that reports the vacuum in the brake booster or a vacuum reservoir. It is a generic code, so it means the same on every make.
Is it safe to drive with U013D?
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 U013D fail an emissions test?
Yes, it can. U013D 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 U013D to fix?
Difficulty: medium. A typical repair takes 0.5 to 2 hours of work. A careful DIY repair is possible with basic tools and a scanner.
Will U013D clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.