Emissions Control System Fault
There’s a fault in the emissions control system, affecting performance and emissions.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine control module (ECM) is detecting that the emissions control system isn’t working properly. This could mean the exhaust gases aren’t being cleaned effectively, which can lead to higher pollution and other performance issues.
What the computer is actually seeing
The ECM monitors inputs from various sensors that measure exhaust gas composition—like O2 sensors—and compares these values against expected parameters. If readings are outside the expected range, usually by more than 10% off, it triggers this code.
What a healthy reading looks like
Oxygen sensors should show voltage levels oscillating between 0.1V and 0.9V; a steady state at either voltage indicates a fault.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 1Check for any exhaust leaks upstream of the O2 sensors—repair as necessary.
- 2Inspect wiring and connectors for the emissions control sensors, specifically for corrosion or damage—repair if found.
- 3Monitor oxygen sensor voltage while running the engine: should oscillate between 0.1V and 0.9V. If steady, replace that sensor.
- 4If sensors are working fine, check the exhaust system for blockages or issues with the catalytic converter that may affect readings.
Common causes
- Damaged wiring to the emissions sensors
- Faulty oxygen sensors
- Exhaust leaks
- Bad ECM programming or failure
- Failed catalytic converter
Typical repair cost
$$$
Related codes
Frequently asked questions
Is it safe to drive with this code active?
It is better to address the issue soon as it can lead to decreased performance and higher emissions.
Will this code come back after I clear it?
If the underlying issue isn't fixed, it's likely the code will return.
Why does this code appear when I have a problem with the O2 sensor?
The O2 sensor is critical for emissions monitoring—if it fails, the ECM sees incorrect readings and sets this fault.
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