U04B6: Invalid Data Received From Catalyst Heater Control Module

What it means

A control module received invalid data from the catalyst heater control module. The code identifies a data validity fault; the specific affected function depends 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 catalyst heater control module reports information about the system that helps warm the catalytic converter for emissions control. U04B6 is set when a receiving module considers that information invalid, which may affect catalyst warm-up without establishing that the heater itself is faulty.

Common causes

Most likely first.

1. Fault in the transmitting module
2. Network wiring or connector fault
3. Module power or ground fault
4. Software or configuration mismatch

Symptoms

• An emissions or engine warning may appear
• Catalyst warm-up or emissions control may be affected

How to diagnose it

1. Record freeze-frame data and scan engine and emissions modules for related catalyst heater or communication codes.
2. Check live data for catalyst heater control module status and note whether its reported values are missing, implausible, or flagged invalid.
3. Inspect the module connector and nearby network harness for heat damage, corrosion, loose pins, or chafing.
4. Check the module's power and ground against the manufacturer's specification.
5. Test the relevant network wiring and connectors for opens, shorts, or poor connections using the vehicle wiring information.
6. If wiring and supplies are sound, check applicable software or configuration updates before replacing a module.

Common fixes

• Reconnect or repair a loose or corroded catalyst heater control module connector.
• Repair heat-damaged or chafed network wiring.
• Restore a faulty module power or ground connection.
• Correct an applicable software or configuration mismatch.
• Replace the catalyst heater control module or reporting module only after testing identifies the faulty source.

Can I keep driving?

A short drive may be reasonable if the engine runs normally and no other warning is present, but avoid extended use because catalyst warm-up and emissions control may be affected. Address it promptly if the engine warning persists or the vehicle develops other symptoms.