U013D

Code

Generic U — Network/User

Lost Communication With Vacuum Sensor A

Brand: Generic

Type: U — Network/User

Views: UK: 21 EN: 31 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Broken or intermittent CAN/LIN/serial data communication between sensor/module and control module
Faulty Vacuum Sensor A (internal electronics or firmware failure)
Power (battery/ignition) or ground loss to the sensor/module
Corroded, bent, or loose connector pins or damaged wiring harness
Short to voltage or ground on the communication bus
Module awake/sleep state or configuration issue (module not awake or not configured on bus)

Symptoms

U013D diagnostic trouble code present
Related system warnings or reduced function (e.g., reduced brake assist, warning lamp, limp mode)
No live data or stale/blank values for Vacuum Sensor A in scan tool
Intermittent operation of systems that rely on vacuum/pressure input
Other communication (U0xxx) trouble codes present for nearby modules

What to check

Read freeze frame and full DTC list; note time, conditions, and any related U-codes
Use a scan tool to confirm Vacuum Sensor A live data is absent or stale
Check for other affected modules on the same bus (scan for U-codes)
Visually inspect connectors and harness to Vacuum Sensor A for corrosion, damage, or moisture
Verify fuses and relays supplying the sensor/module
Check module power and ground with a DMM while key is ON

Signal parameters

Expected: sensor/module transmits valid data messages on vehicle network (CAN/LIN) at a regular interval — typically several Hz (common ranges 1–20 Hz depending on vehicle)
CAN bus physical layer: differential voltages ~2.5 V idle, valid CAN frames at vehicle bus bitrate (commonly 125/250/500 kbps) — bus activity should be present
If sensor uses analog output: typical signal range ~0.5–4.5 V representing vacuum/pressure; reference and ground should be stable (check spec for vehicle)
Power supply: sensor may use 5 V reference or vehicle battery/ignition power depending on design — verify correct supply voltage at connector

Diagnostic algorithm

Confirm code with an OEM-capable scan tool and record freeze-frame and any related codes.
Check for multiple U-codes on the same network — if many modules are lost, investigate main CAN gateway, power, or ground first.
With key ON, check fuse(s) and relays supplying Vacuum Sensor A; replace if blown or faulty.
Visually inspect sensor connector and wiring for corrosion, bent pins, moisture, or physical damage.
Use a scan tool to request Vacuum Sensor A data; if no response, try waking modules (some require a manufacturer tool to wake/sleep).
Verify power and ground at the sensor connector with a DMM. Repair any open/poor grounds or missing power.
Check for communication on the network: use a scan tool to view bus traffic or an oscilloscope/CAN analyzer to verify message IDs and waveform integrity at the sensor connector and at the control module/gateway.
Perform continuity and short-to-voltage/ground tests on communication wires between sensor and gateway/module. Repair any wiring faults.
If wiring and power are good but no communication, swap in a known-good sensor/module (if available) or follow OEM module reprogramming/wake procedures.
After repairs, clear codes and road-test; re-scan to confirm U013D does not return and system functions are restored.

Likely causes

Disconnected or corroded connector at Vacuum Sensor A
Damaged CAN/LIN wiring (chafing, pinched, broken) between sensor and gateway/ECM
Loss of sensor power or ground due to blown fuse or broken wire
Failed vacuum sensor/module electronics resulting in no bus messages
Bus termination or shorting problem preventing proper message transmission

Fault status

⚠️ Status

Control module reports no valid communication from Vacuum Sensor A. Systems depending on that input may operate in a fallback or reduced mode. Affected functions and severity vary by vehicle. Diagnostic scan tool access required.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours