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Home / DTC / U011A — Lost Communication With Exhaust Gas Sensor Module A

U011A — Lost Communication With Exhaust Gas Sensor Module A

Detailed page for trouble code U011A.

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Code

U011A

Generic U — Network/User

Lost Communication With Exhaust Gas Sensor Module A

Brand: Generic
Type: U — Network/User
Views: UK: 16 EN: 42 RU: 16
AI status
Completed
ready
Completed 100%
Page language: EN

Causes

  • Faulty Exhaust Gas Sensor Module A
  • Power supply or ground fault to the sensor module (blown fuse, open circuit)
  • Damaged or corroded connector at the sensor module
  • Open, short or intermittent wiring on the communication bus (CAN or LIN) to the module
  • Bus termination or bus wiring fault (short to battery/ground, high resistance)
  • Another module on the network causing bus errors or bus-off condition

Symptoms

  • Malfunction Indicator Lamp (MIL) or service light illuminated
  • Missing or invalid exhaust gas sensor readings on a scan tool
  • Emissions control warnings, DPF/regen faults or reduced engine performance in some systems
  • Possible limp-home mode or restricted functionality of downstream systems
  • Pending or stored U-codes for communication with the exhaust sensor module

What to check

  • Read freeze frame and all related codes with a capable scan tool; note other network codes
  • Verify the Exhaust Gas Sensor Module A appears on the network list (module present) using a scan tool
  • Check vehicle battery voltage and charging system before diagnosing network issues
  • Inspect fuses and relays that supply power to the exhaust gas sensor module
  • Visually inspect module connector and wiring for corrosion, damage, pin push-out or moisture
  • Check continuity and resistance of power and ground circuits to the module

Signal parameters

  • Module presence/ID on vehicle network (appears in scan tool network listing)
  • Power supply voltage to module (approx. vehicle battery voltage, typically 12–14.5 V with engine running)
  • Ground continuity (low resistance to chassis ground)
  • Bus voltages at idle: CAN_H and CAN_L should be near nominal recessive levels and show complementary differential activity when messages are present
  • Message frequency/IDs expected from the module (verify expected messages are present using a capable diagnostic tool or oscilloscope)
  • Error frame count or bus-off conditions reported by gateway/other modules

Diagnostic algorithm

  1. Retrieve all stored and pending trouble codes and freeze frame data. Record any other U-codes or related P-codes.
  2. Attempt communication with the Exhaust Gas Sensor Module A using a scan tool. Note whether the module responds or times out.
  3. Visually inspect the module connector and wiring harness for damage, corrosion or contamination. Repair any visible faults.
  4. Verify module supply: check fuses and measure battery voltage at the module power pin and verify good ground at module ground pin.
  5. Check for proper network operation: at the module connector measure CAN/LIN bus voltages and compare to known-good values; use an oscilloscope to confirm valid data frames and absence of excessive noise or error flags.
  6. If bus voltages or signals are abnormal, isolate wiring between the module and the nearest gateway or junction connector. Repair shorts, opens, or high resistance joints as found.
  7. If wiring and power/ground are good but the module does not respond, try a module reset by disconnecting battery power for a short period only per vehicle manufacturer guidance, then retry communication.
  8. If the module still does not communicate, check for other modules causing bus errors by disconnecting suspect modules one at a time (follow safe procedures) or inspecting gateway diagnostic information.
  9. If module is confirmed faulty, replace the Exhaust Gas Sensor Module A. After replacement, program/reflash or configure the new module if required by the manufacturer.
  10. Clear codes, perform relevant relearn procedures, and test drive to confirm repair. Re-scan to ensure no recurrence.

Likely causes

  • Connector or wiring issue between module and network (most common)
  • Blown fuse or removed power/ground to the module
  • Module has failed or gone into a non-responsive state
  • CAN/LIN bus interference or missing termination resistor

Fault status

⚠️ Status
Lost communication with Exhaust Gas Sensor Module A — no response on vehicle communication bus (CAN/LIN).
🟡 Repair difficulty: Medium
⏱️ Diagnostic time: 1.0-3.0 hours

Similar codes

U0100 U0101 U0121 U0073
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