Diagnosis
Whenever your PCM registers the P0430 code and activates the check engine light, the first step is appropriately diagnosing what’s causing the catalyst system malfunction.
However, it’s not an easy DIY diagnosis and repair. It’s best to have a certified mechanic look into the issue.
Whether you drive a Toyota, Ford, or Mercedes, here’s how a mechanic will typically diagnose and fix the catalyst system efficiency code:
Step 1: Check That No Other Codes Are Present
They’ll use a scan tool to verify that the P0430 error code is the only code present. If your PCM has registered other codes, the mechanic will fix them first.
Step 2: Check The Exhaust System
If no other codes are present on the scan tool, your mechanic will check the exhaust system for any damage or vacuum leak. They’ll inspect the exhaust manifold, head gaskets, exhaust pipes, and hoses.
Step 3: Check The Oxygen Sensor
Next, the mechanic will use a digital multimeter to read the voltage of the downstream oxygen sensor (rear O2 sensor.)
When the catalytic converter is running correctly, the downstream O2 sensor (rear oxygen sensor) produces a steady voltage of 0.45V. However, if the voltage fluctuates between 0.1V to 0.9V, your catalytic converter needs a replacement.
Sometimes, a bad O2 sensor (rear sensor) may also be at fault. So ask your mechanic to check each O2 sensor during the diagnosis.