P0432: Main Catalyst Efficiency Below Threshold (Bank 2)

P0432 means the main catalytic converter on Bank 2 has dropped below the efficiency threshold the ECU expects. Bank 2 is the cylinder bank that does not contain cylinder 1, so P0432 only applies to V6, V8, V10, V12, or certain flat engine layouts. It is the Bank 2 equivalent of P0422.

P0432 is a emissions-related diagnostic trouble code classified as moderate severity. When your vehicle's ECU detects this condition, it stores P0432 and illuminates the check engine light.

If your vehicle has triggered P0432, you may notice one or more of these symptoms:

• Check engine light illuminated
• Slight drop in fuel economy
• Rotten-egg sulfur smell from exhaust
• Possible rattling from under the Bank 2 side of the car (substrate breaking up)
• Failed emissions or periodic technical inspection

Here are the most common causes of P0432, ranked by how likely they are to be the culprit:

Generally yes, for short-term driving. Safe for normal driving. The check engine light will prevent emissions or periodic technical inspection passage. If rattling appears from under the floor on the Bank 2 side, the converter substrate may be breaking apart and replacement should be prioritised.

Follow these steps to pinpoint the root cause of P0432:

1. Confirm the engine actually has Bank 2 (V6, V8, V10, V12, or flat layout). On inline engines P0432 indicates a wiring or scan-tool fault
2. Read freeze frame data and check for companion codes (P0431, P0430, Bank 2 misfires, Bank 2 lean or rich)
3. Inspect the full Bank 2 exhaust run for leaks, particularly at flange joints, slip-fit connectors, and flex pipe sections
4. Graph the Bank 2 downstream O2 sensor at steady 2,000 to 2,500 RPM. A healthy main cat keeps it stable around 0.4 to 0.6 V
5. Compare Bank 1 vs Bank 2 fuel trims. If Bank 2 long-term fuel trim is consistently 8 percent or more above Bank 1, the underlying mixture imbalance is degrading the Bank 2 cat

Repair costs for P0432 vary depending on the root cause and your vehicle. Here are typical estimates:

P0432 behaves differently depending on your vehicle. Select your car below for model-specific causes, known issues, and adjusted cost estimates:

These codes are often seen alongside P0432 or indicate related issues: