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PO430 Fault Code on 1997 Chevrolet 5.7L - Passenger Side Catalyst System Issue

Model: 97 Chevy Fault Code: P0430 Posted: 2006-10-21 05:30

After replacing both front and rear oxygen sensors (passenger side) on my 1997 Chevrolet with a 5.7L V8 engine, I continue to receive the PO430 diagnostic code after the vehicle warms up and while driving on highways. The issue appears specifically when I release the accelerator pedal. Vehicle mileage: 125,000 miles; service history includes CK1500 maintenance. I'm concerned about potential exhaust system leaks or sensor misalignment causing this persistent fault code.

Related fault codes
P0430
Comments (6)
Anonymous 2006-10-21 06:29

An exhaust leak ahead of the oxygen sensors could be the cause. How old is your catalytic converter? A leaking converter may lead to incorrect readings and trigger the PO430 code.

Anonymous 2006-10-21 07:05

The catalytic converter was recently replaced and is brand new. I've confirmed it's not the issue.

Anonymous 2006-10-21 08:06

Double-check that you're diagnosing the passenger side — Bank 2 — as PO430 specifically refers to the second cylinder bank, which is on the passenger side of a 1997 Chevrolet 5.7L engine.

Anonymous 2006-10-21 08:37

For GM vehicles like this, PO430 relates to Bank 2 (passenger side), specifically the #2 cylinder bank. This helps confirm the correct sensor and system being monitored.

Anonymous 2006-10-21 08:46

Exhaust leaks ahead of the O2 sensors — such as a cracked manifold, converter joint, or exhaust donut — are common causes. The PO430 code often indicates the catalytic converter is running too cold due to an exhaust leak. Other possibilities include aftermarket converters not reaching optimal temperature, vacuum leaks from the intake system, dirty MAF sensor, EGR valve malfunction, faulty coolant temperature sensor, or a failed thermostat. These factors can all interfere with emissions readings and trigger this code.

Anonymous 2006-10-21 09:27

I'm going to systematically check these other components — including vacuum lines, intake system, MAF, EGR, and cooling system — to identify any contributing issues.