Which side of the engine is bank 2?

It is the bank that does not contain cylinder 1, and that is the only part of the answer that is universal. Where cylinder 1 sits depends entirely on the manufacturer's numbering scheme, so bank 2 is the passenger side on some vehicles, the driver side on others, and the rear bank on a great many transverse V6 installations. Look up the numbering for your exact engine rather than assuming, because this is the single most common way people end up working on the wrong side.

Does P0435 mean I need a catalytic converter?

No, and this is the expensive misreading of the code. P0435 says the module cannot read a thermometer on bank 2. It says nothing about whether the converter is converting. Bank 2 conversion performance is judged by P0430, P0432 and P0433. If none of those are present, there is no evidence against the converter at all. Fix the sensor circuit, clear the code, and let the monitor run before anyone quotes exhaust parts.

Can I just swap the two sensors to test it?

Usually yes, and it is the best test available on this code. The two catalyst temperature sensors on a V engine are commonly the same part, so swapping them and clearing the codes tells you whether the fault travels with the sensor or stays with the side. Check the part numbers first, take care with seized threads on an old exhaust, and let everything cool properly before starting.

Is it safe to keep driving with P0435?

In the short term, generally yes. The sensor is a monitoring device rather than something the engine depends on to run, so the vehicle usually drives normally. The two real costs are that emissions monitors will not complete, so the vehicle cannot pass a test, and that the module loses one of its ways of noticing an overheating converter on that bank. If the engine is also misfiring or running rich, treat it as urgent rather than routine, because those are exactly the conditions the protection exists for.

OBD-II trouble code

P0435: Catalyst Temperature Sensor (Bank 2)

The module has lost a usable signal from the catalyst temperature sensor on bank 2. The part is cheap and the job might not be, because on most V engines the first cost driver on this code is not the sensor — it is which side of the engine bay it lives on.

Medium severityPowertrainEmissions / CatalystDrivable short-term

Quick facts

System: Powertrain
Category: Emissions / Catalyst
Severity: Medium severity
Drivable: Usually safe to drive short-term
Repair cost range: $120 – $800
DIY difficulty: Intermediate DIY

What does P0435 mean?

This is the bare circuit code for the bank 2 catalyst temperature probe. It sets when the signal is not merely questionable but unusable — reading as open, shorted, or parked at a value that could not correspond to any temperature a real exhaust has ever been. The module has not concluded that anything is wrong with the converter. It has concluded that it can no longer see the converter's temperature.

The first thing to settle is physical, not electrical: where is bank 2? The definition is unambiguous — it is the cylinder bank that does not contain cylinder 1 — but cylinder numbering is manufacturer-specific and there is no universal convention. Some makers number front to back down one bank and then the other; some alternate side to side along the crankshaft. The result is that bank 2 is the passenger side on one vehicle and the driver side on the next, and on a transverse V6 it is very often the rear bank, tucked against the bulkhead. Look the numbering up for your specific engine before lifting a single tool. Working confidently on the wrong side of the engine is the most common way an afternoon disappears on this code, and it costs the same whether you are doing it yourself or paying someone.

That geometry, once established, dominates the price. On a longitudinal V8 both sensors are reasonably accessible and the two sides cost about the same to service. On a transverse V6 the rear bank sensor may sit behind the engine with the exhaust manifold, heat shielding and half the intake tract in the way, and what is a twenty-minute job on bank 1 becomes a two-hour job on bank 2. When a quote for this code seems high relative to the part price, the labour is usually the honest reason rather than a padded one.

The sensor itself is a simple device — a two-wire thermistor or thermocouple with no heater circuit of its own, which immediately removes the failure mode that dominates the oxygen sensors sitting nearby. What it has instead is a very bad address. It is threaded into the hottest pipework on the vehicle, its lead is routed along that pipework, and it cycles between ambient and several hundred degrees every time the engine runs. The failures follow from that and from almost nothing else: the lead chafes where it rests against hot metal, the connector corrodes, the tip cracks from thermal shock, or the threads seize into the bung so completely that extraction becomes the job.

There is one test available here that is not available on the bank 1 version of this code, and it settles the diagnosis without a specification sheet. The two catalyst temperature sensors on a V engine are usually the same part number. Swap them side to side. If the fault moves to bank 1 with the sensor, the sensor is bad. If P0435 stays on bank 2 with a known-good sensor fitted, the sensor was never the problem and the fault is in the harness, the connector or the module input. On a vehicle where bank 2 access is poor, the honest sequence is to test from the bank 1 side first and only go around the back once you know what you are going back there for.

Common causes

Sensor lead chafed through where it runs against the bank 2 exhaust pipe or a heat shield
Corroded, wet or heat-damaged connector at the bank 2 sensor
Sensor element failed open internally after years of thermal cycling, or a cracked tip
Short to ground through damaged insulation, with the exhaust acting as the return path
Connector left unlatched or a terminal backed out after previous work on the rear bank
Harness damaged during intake manifold, spark plug, manifold gasket or converter work on bank 2
Open in the signal or ground circuit somewhere along the longer bank 2 run back to the module
Module input circuit failure, which is genuinely rare and belongs last on the list

Symptoms

Check engine light with P0435 stored
Bank 2 catalyst temperature displayed as a fixed extreme value, or as no value at all
Bank 1 temperature reading normally on the same scan tool screen, which is itself a clue
Emissions monitors not completing, so the vehicle cannot be presented for a test
Little or no difference in how the vehicle drives
Loss of the module's converter overheat protection on that bank

Diagnostic steps

1.Confirm which physical bank is bank 2 on this specific engine before touching anything. It is the bank without cylinder 1, and the numbering convention varies by manufacturer.
2.Confirm the vehicle actually has a physical sensor there. Some vehicles display a modeled catalyst temperature calculated from load and airflow, in which case there is nothing in the exhaust to unplug.
3.Compare the live bank 1 and bank 2 catalyst temperature values with the engine cold. Bank 1 sitting near ambient while bank 2 sits at an extreme is a circuit fault, not a temperature difference.
4.Inspect the visible length of the bank 2 sensor lead before any electrical testing. On a wire routed along hot pipework, chafe is both the most likely cause and the easiest to see.
5.Unplug the connector and examine both halves for corrosion, moisture, spread terminals and melted plastic.
6.Measure sensor resistance at ambient and compare it with specification, or with the bank 1 sensor measured the same way — the second sensor is a free reference.
7.Swap the two sensors side to side and clear the codes. If the fault follows the sensor to bank 1, the part is confirmed; if it stays on bank 2, the wiring or the module input is at fault.
8.With the sensor unplugged, check the harness for continuity and for shorts to ground back to the module, giving particular attention to any point where the bank 2 run crosses the engine.
9.Do not condemn the converter on this code. Confirm or exclude P0430 separately before exhaust parts are quoted.

Repair cost

$120 – $800

The part is typically $60 to $250. The labour is what varies, and it varies by bank: half an hour on an accessible longitudinal V8, but an hour and a half to three hours on a transverse V6 where the rear bank sensor is reached past the manifold and heat shielding. That puts the realistic fitted range at $120 to $600, with seized threads as the wild card that can push it further and occasionally turn it into a pipe repair. Harness and connector repairs run $100 to $400, again with a bank 2 premium for access. None of this is converter money, which is the number worth keeping in view.

Estimate your repair

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Open the Repair Cost Estimator with exhaust gas temperature sensor replacement preselected. Adjust labor rate and vehicle category to fit your situation.

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DIY vs shop

This is an intermediate DIY job. It usually involves diagnostic steps, specialty parts, and some careful work in tight spaces. If you have the tools and a service manual or trustworthy video for your specific vehicle, it is achievable in a weekend. Otherwise, a competent independent shop will be faster.