P0430 Code on a Cadillac: Catalyst Efficiency Below Threshold, Bank 2 (Cadillac Guide)

P0430 on a Cadillac is "Catalyst System Low Efficiency, Bank 2" — the engine computer has decided the converter on the side without cylinder 1 is no longer doing its job. Only V6 and V8 Cadillacs can set it. The first trap is location: bank 2 is the passenger side on an Escalade or CTS-V, the front bank on a transverse XT5, XT6, XTS or late SRX, and the driver's side on a CTS or CT6 V6. The second is cause: GM has documented a cracking front converter flange on the XTS and sand-blocked converters on the 6.2L Escalade — and in both cases it says to inspect before buying parts.

What Does P0430 Mean on a Cadillac?

Each bank of a Cadillac V6 or V8 has its own catalytic converter, with an oxygen sensor ahead of it and another behind it. The engine control module (ECM) judges each converter by how much oxygen it can store. A worn converter lets the downstream sensor mirror the upstream one far too quickly.

GM's 2008 OBD documentation for the 3.6L LY7 — the V6 in mid-2000s CTS, STS and SRX models — lists separate catalyst tests for bank 1 (P0420) and bank 2 (P0430). The test runs at a warm idle with the vehicle stopped and the throttle closed. The ECM measures the response-time difference between the bank's pre- and post-catalyst sensors, scales it between a "best failing" and "worst passing" converter from calibration tables, and produces a normalised ratio where 1 is good and 0 very bad. P0430 sets when the filtered ratio falls below 0.35. It is a Type A code on that engine, so one failed test can light the lamp. GM's 2018 calibration summaries show some newer engines running the same 0.35 check during deceleration.

GM blocks the test while misfire, fuel trim, oxygen sensor, MAF and many other codes are set. If P0430 shares the scan with any of those, they come first. For the general GM picture, see our P0430 GM diagnosis guide.

Where Bank 2 Is on Your Cadillac

• Escalade, Escalade ESV/EXT and CTS-V (small-block V8): cylinder 1 is at the front of the driver's side, so bank 2 is the passenger side (cylinders 2-4-6-8).
• Transverse 3.6L V6 (2010–2016 SRX, XTS, XT5, XT6): bank 2 holds cylinders 2-4-6 and is the front bank, nearest the radiator. GM's own XTS documents describe the left-hand converter as "bank 2 / front."
• Longitudinal 3.6L V6 (CTS, STS, ATS V6, CT6 and the 2004–2009 SRX): bank 1 is the right (passenger) side viewed from the flywheel end, so bank 2 is the driver's side.
• Northstar V8: confirm bank location in the service information for your VIN; we have not verified it from a GM document for this article.
• Four-cylinder Cadillacs (ATS, CTS and CT6 2.0T, XT4, CT4, CT5 2.0T) have one converter and cannot set P0430. Their catalyst code is P0420.

Mixing up the banks is the most expensive mistake on this code. Confirm which sensors your scan tool reports as bank 2 sensor 1 and bank 2 sensor 2 before you touch anything.

P0430 Alone vs With P0420

The XTS Front Converter

The XTS with the 3.6L LFX is the Cadillac with the clearest bank 2 converter story. GM's PIP5419 (September 2016) covered 2013–2016 XTS and 2014–2016 Impala models with exhaust noise from cracking at the left-hand (bank 2 / front) converter pipe near the cylinder head mounting flange weld. GM told technicians to verify the exhaust is stock and undamaged and the hangers and mounts are in place, then replace the converter with the latest part — and noted that in rare cases the failure could recur after replacement.

That preliminary information became bulletin 17-NA-321 (latest revision November 2019), covering 2013–2018 XTS (up to an October 1, 2017 build point) and 2014–2018 Impala with the LFX. The condition: an exhaust smell and/or leak, possibly with the MIL on and P0430 and/or P0420 set. The cause: a crack around the converter mounting flange. The fix: visually inspect for cracks and replace the affected converter; if there are no cracks, continue normal diagnosis. GM lists separate service parts for the right and left converters, so make sure the one ordered is for the cracked side.

Because an exhaust leak ahead of the rear sensor lets outside air skew the reading, a cracked flange can set the efficiency code even when the catalyst itself is fine. On an XTS with P0430 and an exhaust smell, look at the front converter flange before anything else.

Escalade and Other GM Findings

Sand past the air filter: 6.2L Escalade and CTS-V

Bulletin 16-NA-111 (revised March 2019) covers the 2015–2018 Escalade 6.2L and the 2016–2019 CTS-V with P0420 and/or P0430. GM's cause is sand or debris entering the air box and bypassing a filter that isn't sealing, damaging the oxygen sensors and blocking the converters. GM's instruction: do not replace any parts until the air filter housing is validated as completely sealed — check the cover tabs and fasteners, the filter seal and sealing surface, and look for dirt in the cover and outlet duct.

False codes after break-in: Escalade 2002–2018

PIP3119P covers 2002–2018 Escalade V8s. GM disables P0420 and P0430 for the first hour of engine run time on a new vehicle so the converters can break in. A power loss during manufacturing, or a fresh converter replacement, can let the test run before break-in and set a false P0430. GM's fix is to clear the code and run a highway drive cycle: 25–30 minutes at speed, a one-minute shutoff, 10–15 more minutes, another shutoff, then normal driving to run the test.

Coil ground for the affected bank

PIP5232C covers 2016 and prior GM cars where a converter came apart or set P0420/P0430 with no apparent reason; NHTSA indexes it to the ATS, CTS and XTS. GM's recommendation is bank-specific: inspect the ignition coil ground on the engine block for the bank with the concern for a poor crimp or corrosion, then tighten it to spec. A weak ground means weak spark on that bank, unburned fuel in that converter and overheating — and a new converter at risk too.

After an engine failure

Bulletin 06-06-01-010D tells technicians replacing an engine with close-coupled converters to inspect each converter, because debris or melted substrate can be drawn into the new engine. If your P0430 appeared after major engine work, that converter deserves a close look.

Older Cadillacs

NHTSA indexes GM documents naming P0420/P0430 for the 2004 SRX and XLR with the 4.6L Northstar (01979), 2004–2006 CTS and SRX (3679) and 2001–2005 Escalades in the Detroit area (3107). We have only the index entries.

Recalls and Warranty

Check for open emission recalls before diagnosing: 07027A covered certain 2004 SRX 3.6L models for possible failure of the left or right converter; 17405 covered certain California 2018 XTS models that may have the wrong front converter; and N232419720 covers certain 2022–2023 Escalade and ESV 6.2L L87 models that received an incorrect converter service part. None names P0430, but each involves the converters.

Under the EPA's federal emissions warranty, catalytic converters are "specified major emission control components" covered for 8 years or 80,000 miles on 1995 and newer vehicles, for defects in materials or workmanship. Damage caused by misfire, oil burning or impact is treated differently, and some states set longer terms. On a newer Cadillac, ask the dealer before paying for a bank 2 converter.

Symptoms of P0430

• Check engine light, often with no driveability change
• Exhaust smell or leak from the front of the engine on an XTS (17-NA-321)
• Failed emissions inspection
• Rotten-egg smell
• Rattle from a broken converter substrate
• Lack of power if the converter is restricted

Causes and How to Confirm Each

How Is P0430 Diagnosed?

1. Confirm the engine has a bank 2. A four-cylinder Cadillac should not set P0430.
2. Read all codes and freeze frame, and fix misfire, fuel trim, O2 and MAF codes first.
3. Identify bank 2 on your model and its sensors on the scan tool.
4. Check the VIN for emission recalls and bulletins.
5. On an XTS, inspect the front converter flange for cracks (17-NA-321).
6. On a 6.2L Escalade or CTS-V, validate the air box seal (16-NA-111).
7. Look for exhaust leaks on bank 2 up to the rear sensor.
8. Review bank 2 misfire history and inspect the bank 2 coil ground (PIP5232C).
9. Compare both banks' sensors at operating temperature. The bank 1 side gives you a built-in comparison.
10. Clear codes and drive so GM's catalyst monitor can run, using PIP3119P's drive cycle after a new converter.

Parts and Cost

GM Documents That Name P0430 on Cadillac Models

Have a dealer check your VIN against current bulletins, recalls and special coverages rather than relying on any article, including this one.

What Other P0430 Pages Get Wrong

• Putting bank 2 on the driver's side of an Escalade. On GM V8s, bank 2 is the passenger side.
• Putting bank 2 at the firewall on an XT5 or XTS. On the transverse 3.6L it is the front bank — GM's XTS documents say so.
• Listing P0430 for four-cylinder Cadillacs. They have only bank 1.
• Replacing the converter first. GM says check the coil ground, the air box seal or the flange first, depending on the model.
• Replacing both converters for a single-bank code. P0430 alone points at bank 2.
• Forgetting the emissions warranty. Converters are covered for 8 years or 80,000 miles against defects under federal rules.

Frequently Asked Questions

Which side is bank 2 on my Escalade?

The passenger side. GM small-block V8s put cylinder 1 at the front of the driver's side, so that is bank 1.

Which converter is bank 2 on an XTS or XT5?

The front one, nearest the radiator. GM's XTS bulletins call it the left-hand, "bank 2 / front" converter.

Why does my XTS smell like exhaust and show P0430?

GM's 17-NA-321 describes exactly that on 2013–2018 XTS models: a crack around the converter mounting flange. A dealer can inspect it visually.

Can I drive with P0430?

Usually, if the engine runs normally, but an exhaust leak near the engine can let fumes into the cabin and a restricted converter can cut power. Diagnose it soon.

Do I need to replace both converters?

Not for P0430 alone, unless both test bad. If P0420 and P0430 are both set, look for a shared cause such as sand, oil burning or a fuel trim fault first.

Is P0430 covered by warranty?

Converters carry a federal 8-year/80,000-mile defect warranty, and some states go further. Damage from misfire or oil burning is treated differently. Ask a dealer to check your VIN for recalls and coverage.