U011A: Lost Communication With Exhaust Gas Temperature Sensor Module

What it means

A control module has lost communication with the exhaust gas temperature sensor module. Exhaust temperature information may be unavailable on vehicles that use this module.

At a glance

• Affects emissions; the car can fail an emissions test

How it works

The exhaust gas temperature sensor module collects or processes exhaust temperature readings for the engine or aftertreatment system. This code sets when another module stops receiving expected messages from that module, leaving temperature information unavailable and potentially affecting emissions control.

Common causes

Most likely first.

1. Loss of module power or ground
2. Open, shorted, or damaged communication wiring or connector
3. Module or gateway fault

Symptoms

• Warning lights or messages
• Communication faults in other modules
• Emissions or aftertreatment functions may be affected

How to diagnose it

1. Scan all modules for U011A and aftertreatment codes, noting which modules have lost contact with the exhaust gas temperature sensor module.
2. Review freeze-frame data and emissions warnings to see whether the communication fault coincided with a regeneration or other aftertreatment event.
3. Inspect the temperature module's connectors and harness near the exhaust for heat damage, chafing, corrosion, or loose terminals.
4. Check the module's power and ground circuits against the manufacturer's specification.
5. Test its network wiring for opens, shorts, and poor connections, following the vehicle's circuit diagram and procedure.
6. If supply and network tests pass, check gateway operation and the temperature sensor module with vehicle-specific diagnostics.

Common fixes

• Repair heat-damaged or chafed wiring and secure the harness away from hot exhaust components.
• Clean, reconnect, or repair a loose or corroded module connector.
• Restore a failed power or ground circuit to the module.
• Repair a confirmed network or gateway fault, or replace and configure the module if diagnostics confirm it has failed.

Can I keep driving?

If an emissions or aftertreatment warning appears, avoid prolonged heavy-load driving because missing exhaust temperature data can interfere with monitoring or aftertreatment operation. Follow any warning message and address the fault promptly.