U068E: Lost Communication With EGR Temperature Sensor B

What it means

The vehicle bus reports loss of communication with smart EGR temperature sensor B (typically post-cooler). EGR cooling diagnostic switches to model-based estimation.

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

EGR temperature sensor B is a smart sensor that typically reports the temperature after the EGR cooler over the vehicle bus. This code sets when its messages are lost, so the EGR cooling diagnostic has to estimate temperature rather than compare a live post-cooler reading.

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. Save freeze-frame data and scan all modules for communication codes to determine when post-cooler sensor B stopped reporting and whether the fault is shared across the bus.
2. Inspect sensor B's post-cooler connector and harness for loose pins, corrosion, heat damage, or chafing.
3. Check the sensor module's power and ground according to the manufacturer's procedure to rule out a lost supply.
4. Inspect the communication wiring and splices to sensor B for opens or shorts, then test the bus circuit as specified by the manufacturer.
5. If wiring, power, and ground are sound, verify with a capable scan tool that sensor B is unreachable before replacing its module.

Common fixes

• Secure or repair the post-cooler sensor B connector and damaged terminals.
• Repair an open, short, or damaged splice in sensor B's communication wiring.
• Restore the sensor module's power or ground.
• Replace EGR temperature sensor B if it remains offline after the circuit checks pass.

Can I keep driving?

A gentle short drive may be reasonable if the vehicle runs normally, but avoid heavy loads if EGR or exhaust warnings are present. The missing post-cooler reading can impair EGR cooling checks and emissions control, so arrange repair soon.