U013D: Lost Communication With Vacuum Sensor A

What it means

ECU lost CAN communication with vacuum sensor A (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 A reports vacuum-related data to other vehicle systems, and on some vehicles it communicates over the data network. U013D sets when expected messages from sensor A are missing; the affected function depends on which systems use its data.

Common causes

Most likely first.

1. Sensor unpowered or bus connection broken
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 to identify U013D and any related vacuum, power, or network faults.
2. Check battery and charging-system condition because low voltage can interrupt communication with a networked sensor.
3. Locate vacuum sensor A using vehicle service information and inspect its connector, harness, and vacuum connection for looseness, damage, contamination, or leaks.
4. Check sensor A's power and ground circuits, if equipped, against the manufacturer's specification.
5. Test its network wiring and any gateway path for opens, shorts, or poor connections using the manufacturer's procedure.
6. If its connections and supplies are sound, check whether sensor A communicates with a scan tool before considering replacement.

Common fixes

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

Can I keep driving?

Drive cautiously until you know which system depends on vacuum sensor A and whether its function is affected. If braking assistance or another safety-related function changes, stop driving and arrange inspection.