U069B: Lost Communication With Exhaust Gas Temperature Sensor Bank 1 Sensor 4

What it means

Communication with exhaust gas temperature sensor bank 1 sensor 4 has been lost. The resulting effects depend on how the vehicle uses that sensor’s data.

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

Exhaust gas temperature sensor bank 1 sensor 4 monitors exhaust temperature at its own position on bank 1 and reports it over the vehicle bus. This code sets when the control system can no longer communicate with bank 1 sensor 4, so any strategy relying on that sensor’s reading may use a substitute value or be restricted.

Common causes

Most likely first.

1. Bus wiring open or shorted
2. Module without power or ground
3. Module failed

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. Record freeze-frame data and scan engine and emissions modules for other exhaust-temperature, aftertreatment, and network codes.
2. Check live data specifically for bank 1 sensor 4’s communication status and temperature, comparing it with other exhaust-temperature readings if available.
3. Use vehicle service information to locate bank 1 sensor 4, then inspect its connector and wiring for heat damage, chafing, or corrosion.
4. Verify the sensor’s specified power and ground, as a supply fault can make the module disappear from the network.
5. Test the sensor’s bus circuit for an open or short using the wiring diagram and manufacturer procedures.
6. If wiring and supply are sound, confirm whether bank 1 sensor 4 itself has failed.

Common fixes

• Reconnect or clean the bank 1 sensor 4 connector.
• Repair damaged or heat-affected bus wiring to bank 1 sensor 4.
• Restore the sensor’s power or ground connection.
• Replace exhaust gas temperature sensor bank 1 sensor 4 if its circuit and supply are sound and the module is faulty.

Can I keep driving?

A short trip may be reasonable if the vehicle has no temperature warnings or drivability problems, but have the fault diagnosed soon. Avoid heavy loads if an emissions or reduced-power warning appears, because bank 1 sensor 4 data may be used for exhaust protection or aftertreatment control.