The largest online repair guide library for every car

About us
Contact support
FAQ
Sign up
Sign in

2016 ATS-V P0420 Code - Catalyst System Efficiency Below Threshold

0

Mike T. · rep 0 · May 25, 2:49 AM · 1 replies · solved · Question

Vehicle: 2016 Cadillac ATS-V 3.6L Twin Turbo

Hey everyone,

My 2016 Cadillac ATS-V, 3.6L Twin Turbo, just threw a Check Engine Light. I scanned it with my OBD-II tool, and it's showing a P0420 code: 'Catalyst System Efficiency Below Threshold (Bank 1)'.

The car seems to be running fine, no noticeable loss of power or strange noises. Fuel economy might be slightly worse, but it's hard to tell for sure. I've heard this could be anything from an O2 sensor to a failing catalytic converter itself.

Has anyone with an ATS-V experienced this specific code? What was your fix? I'm hoping it's not the catalytic converter, as those can be pricey on these cars. Any tips on how to diagnose this further before I take it to a shop?

Thanks in advance for any help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 2:49 AM

0

ClearTheCode admin answer:

The P0420 code on your 2016 Cadillac ATS-V indicates that the catalytic converter on Bank 1 is not operating at peak efficiency. While the car may seem to run fine, addressing this promptly can prevent further issues and ensure proper emissions.

Common Causes:

  1. Failing Oxygen Sensor: Often, a faulty upstream or downstream O2 sensor can send incorrect readings, tricking the ECU into thinking the converter is bad. The downstream (post-catalyst) sensor is particularly critical for monitoring converter efficiency.
  2. Exhaust Leaks: Leaks in the exhaust system before or near the catalytic converter can introduce outside air, skewing O2 sensor readings.
  3. Contaminated Catalytic Converter: Fuel additives, excessive oil consumption, or coolant leaks can contaminate the catalyst material, reducing its effectiveness.
  4. Failing Catalytic Converter: Over time, the catalyst material can degrade or melt, leading to reduced efficiency. This is often the most expensive fix.
  5. Engine Misfires: Persistent misfires can send unburnt fuel into the converter, causing it to overheat and fail.

Diagnostic Steps:

  1. Scan for Other Codes: Check for any other pending or active codes, especially O2 sensor codes (P0133, P0137, etc.) or misfire codes (P030X).
  2. Monitor O2 Sensor Data: Using a good scan tool, monitor the live data for both upstream and downstream O2 sensors on Bank 1. The upstream sensor should fluctuate rapidly, while the downstream sensor should show a relatively steady, higher voltage (around 0.6-0.9V) if the converter is working correctly. If the downstream sensor mirrors the upstream, the converter is likely inefficient.
  3. Check for Exhaust Leaks: Visually inspect the exhaust system for any cracks, loose connections, or rust spots.
  4. Inspect Spark Plugs/Coils: Ensure the engine is not experiencing misfires that could be contributing to converter damage.

When to See a Shop:

  • If you've checked O2 sensor data and suspect the converter is truly failing.
  • If you find exhaust leaks that require welding or specialized repair.
  • If you're uncomfortable diagnosing electrical components or exhaust systems yourself.
  • If the Check Engine Light is flashing, indicating a severe misfire that could rapidly damage the converter.

A professional technician can perform a more thorough diagnosis, including backpressure tests and smoke tests, to accurately pinpoint the root cause of the P0420 code.

Menu

Help & account