U013E: Lost Communication With Vacuum Sensor B

What it means

ECU lost CAN communication with vacuum sensor B (often a smart sensor with bus interface). A communication loss with this module breaks any function relying on its data — diagnostic tools may show 'no response' and dependent modules can fall into limp mode.

At a glance

• Usually lights the warning light of the system that lost communication
• Affects emissions; the car can fail an emissions test

How it works

Vacuum sensor B supplies vacuum-related data to systems that use it; on some vehicles it communicates over the data network. U013E sets when expected messages from sensor B are missing, which can affect functions that rely specifically on its readings.

Common causes

Most likely first.

1. Sensor unpowered
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Multiple warning lights may illuminate
• Affected modules may go into limp mode or shut down
• Specific functions inoperative depending on module
• Diagnostic tools may show communication faults

How to diagnose it

1. Scan all modules and review freeze-frame data for U013E and related vacuum, power, or network faults.
2. Check battery and charging-system condition because low voltage can disrupt communication with a networked sensor.
3. Locate vacuum sensor B from vehicle service information and inspect its connector, wiring, and any vacuum line for damage, looseness, contamination, or leaks.
4. Check sensor B's power and ground circuits, if equipped, against the manufacturer's specification.
5. Test the network wiring to sensor B and any gateway path for opens, shorts, or poor connections using the manufacturer's procedure.
6. If supplies and wiring are sound, check whether sensor B communicates with a scan tool before considering replacement.

Common fixes

• Reconnect or repair a loose or damaged vacuum sensor B connector.
• Repair a damaged harness or network connection to sensor B.
• Repair a leaking or disconnected vacuum line at sensor B, if fitted.
• Restore the sensor's power or ground supply if faulty.
• Replace vacuum sensor B if it remains unresponsive with sound connections and supplies.

Can I keep driving?

Use caution until you establish whether a system relying on vacuum sensor B is affected. If braking assistance or another safety-related function changes, stop driving and arrange inspection.