2022 Highlander XLE rattling noise from exhaust and sulfur smell

ClearTheCode admin answer:

The rattling noise from underneath your 2022 Toyota Highlander XLE combined with a sulfur (rotten egg) smell from the exhaust are classic symptoms pointing towards issues with your catalytic converter. Here's a breakdown:

1. Catalytic Converter Failure:

   • Cause (Rattling): Inside the catalytic converter are ceramic substrates coated with precious metals. Over time, these substrates can break apart, especially due to impacts or excessive heat. The broken pieces then rattle around inside the converter housing.
   • Cause (Sulfur Smell): The catalytic converter's job is to convert harmful exhaust gases, including hydrogen sulfide, into less harmful compounds. If the converter is failing or overloaded (e.g., due to an engine running rich), it may not be able to process the sulfur compounds effectively, leading to the rotten egg smell.
   • Diagnostics: A mechanic can physically inspect the catalytic converter for damage and listen for the rattle. They might also check for a P0420 (Catalyst System Efficiency Below Threshold) code, which often appears when the converter is failing, even if it hasn't triggered a CEL yet.

2. Exhaust System Components:

   • Cause (Rattling): While the catalytic converter is a prime suspect, other exhaust components like loose heat shields, hangers, or internal muffler baffles can also cause rattling noises.
   • Action: A visual inspection of the entire exhaust system can identify loose or damaged parts.

3. Engine Running Rich:

   • Cause (Sulfur Smell): An engine that is consistently running 'rich' (too much fuel, not enough air) can overwhelm the catalytic converter, leading to the sulfur smell. This could be due to faulty oxygen sensors, a leaky fuel injector, or a problem with the MAF sensor.
   • Diagnostics: A mechanic can check fuel trims and oxygen sensor readings using a diagnostic scanner.

When to See a Shop:

• Immediately: A failing catalytic converter can restrict exhaust flow, leading to reduced engine performance, decreased fuel economy, and eventually, a Check Engine Light. If the converter becomes completely clogged, it can cause significant engine damage or prevent the vehicle from running. It's crucial to have your Highlander inspected by a qualified mechanic or Toyota dealership as soon as possible to diagnose and address these issues.