U019D: Lost Communication With Direct Ozone Reduction Catalyst Temperature Sensor

What it means

A control module is not receiving expected messages from the Direct Ozone Reduction Catalyst Temperature Sensor. The code indicates a communication fault; the sensor's role and resulting effects depend on the vehicle.

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

The Direct Ozone Reduction Catalyst Temperature Sensor reports temperature information used by the vehicle's emissions control system. U019D sets when a control module stops receiving expected messages from that sensor; it identifies a communication loss and does not by itself prove the sensor reading is inaccurate or the catalyst has failed.

Common causes

Most likely first.

1. Sensor unpowered or wiring broken
2. Gateway module routing CAN messages incorrectly
3. CAN terminating resistor (120 Ω) drifted out of spec

Symptoms

• Emissions-system warning or message
• Other communication codes

How to diagnose it

1. Save freeze-frame data and scan the emissions and network modules for companion codes, noting whether other messages from the same network are missing.
2. Check scan data for the Direct Ozone Reduction Catalyst Temperature Sensor and confirm whether its status is absent or marked unavailable.
3. Inspect the sensor connector and accessible wiring for heat damage, corrosion, broken conductors, or poor seating near the exhaust system.
4. Check the sensor's specified power and ground circuits and verify continuity of the communication wiring using the manufacturer's procedure.
5. If wiring and supply are sound, check for gateway routing faults and test the network and terminating resistance against the manufacturer's specification.

Common fixes

• Repair heat-damaged or broken wiring and clean or secure the sensor connector.
• Restore the sensor's specified power or ground supply.
• Correct a gateway fault that is blocking the sensor's messages.
• Repair the network or replace the sensor only after its communication failure is confirmed.

Can I keep driving?

The emissions system may not have the temperature information it needs, and an emissions warning may remain on. Avoid ignoring the fault for extended use, and have the system checked if other emissions warnings or drivability changes appear.