<em>Nissan Almera Classic</em>catalyst: how to check, replace or remove without consequences

Nissan Almera Classic (in the back B10, also known as Nissan Sunny or Samsung SM3 in some countries) is one of the most popular budget sedans on the secondary market. However, as these machines age, they often develop problems with catalytic converter, especially on engines QG15DE And QG16DE. A faulty catalyst not only worsens performance and increases fuel consumption, but can also lead to serious engine damage if the first symptoms are ignored.

In this article we will look at how diagnose a catalytic converter malfunction on Almera Classic, what repair methods exist (from replacing with the original to installing a flame arrester), and what to do if, after removing the catalyst, it catches fire Check Engine. We will also provide current prices for spare parts, article numbers of original and analogue parts, and explain why it is sometimes cheaper buy a contract catalyst from disassembly rather than install a new universal one.

Signs of a faulty catalytic converter Nissan Almera Classic

The catalyst fails gradually, and the first symptoms are often attributed to “age-related” engine problems. However there is 5 Key Signs, which directly indicate problems in the exhaust gas aftertreatment system:

• 🔥 Power drop — the car “doesn’t pull” on inclines, accelerates poorly, the engine feels “stifled” (especially at speeds above 3000).
• 🚨 Lit Check Engine with errors P0420 (“low catalyst efficiency”) or P0430 (“failure of the second lambda probe”).
• 💨 Unpleasant smell from the exhaust pipe - hydrogen sulfide ("rotten eggs") or a pungent chemical odor that does not disappear after warming up.
• 🔊 Rattling sound under the bottom during startup or at idle speed - a sign of destruction of the ceramic filling of the catalyst.
• ⛽ Increased fuel consumption (1–2 liters more than usual) due to a violation of the composition of the fuel mixture.

On Almera Classic with motors QG15DE/QG16DE the catalyst most often “dies” after 150–200 thousand km, but with aggressive driving, poor fuel or mechanical damage (for example, after hitting the bottom), this can happen earlier. The most dangerous situation - when the ceramic honeycomb begins to crumble and gets into the cylinders, scratching the walls and pistons. In this case, repairs will cost many times more than timely replacement of the catalyst.

⚠️ Attention: If small ceramic fragments fly out of the exhaust pipe, stop using the vehicle immediately! This is a sign of complete destruction of the catalyst, and further driving may lead to engine jam.

Where is the catalyst located? Nissan Almera Classic B10?

On Almera Classic catalytic converter integrated into exhaust pipe (spider) and is located immediately after the exhaust manifold. This is a typical layout for most Japanese cars of the time. Access to it is difficult due to its close location to the engine and heat shields, so replacement or diagnostics will require lift or inspection hole.

Structurally, the catalyst consists of:

• 🔧 Metal case with flanges for mounting to the collector and resonator.
• 🧱 Ceramic block carrier with a honeycomb structure coated with precious metals (platinum, palladium, rhodium).
• 🔥 Thermal insulation layer, which prevents the body from overheating.
• 📊 Two lambda probes (before and after the catalyst) to monitor the efficiency of exhaust cleaning.

In photographs on the Internet, a catalyst is often confused with resonator or muffler. In order not to be mistaken, remember: a catalyst is first element of the exhaust system after the collector, and he always has thickened middle part (there is a ceramic block there). On Almera Classic it is attached to the manifold on 4 bolts and connects to the resonator through a corrugation.

How to distinguish a catalyst from a resonator?

The catalyst is always located closer to the engine and has a thickening in the middle part (ceramic “filling”). The resonator is thinner, longer and usually located under the passenger compartment. Also, the catalyst has holes for lambda probes, but the resonator does not.

Catalyst diagnostics: how to check without a service station?

If you suspect a bad catalytic converter, first rule out other possible causes (such as a clogged air filter or faulty spark plugs). For self-diagnosis there is 4 reliable methods:

1. Visual inspection. Stop the engine, allow the system to cool, and inspect the catalyst for cracks, dents, or signs of melting. If the case is deformed, most likely the ceramic inside is destroyed.
2. Checking back pressure. Remove the first lambda probe and start the engine. If there is a strong flow of gases from the hole, the catalyst is clogged. Normal pressure at idle speed - no more than 0.3–0.5 kg/cm².
3. Warm-up test. Start the cold engine and touch the catalyst housing with your hand (be careful, it gets hot!). If one part is hot and the other is cold, the honeycomb is clogged or destroyed.
4. Reading errors. Connect the scanner (for example, ELM327) and check errors on lambda probes. Codes P0420, P0430 or P0134/P0135 almost always indicate problems with the catalyst.

For accurate diagnosis you can use endoscope (flexible chamber) to look inside the catalyst through the hole for the lambda probe. If the honeycomb is melted, clogged with soot or crumbled, the part must be replaced. On Almera Classic A situation often occurs when the catalyst is externally intact, but inside the honeycombs are sintered due to low-quality fuel or oil burns (when oil enters the exhaust through the piston rings).

Original catalyst vs. universal vs. flame arrester: what to choose?

When the diagnosis is confirmed, the question arises: what to replace the faulty catalyst? Each option has pros and cons:

Option	Pros	Cons	Cost (RUB)
Original catalyst (20030-4M000 or 20030-4M001)	🔹 Full compliance with factory parameters 🔹 Warranty 1–2 years 🔹 No problems with ECU firmware	❌ Very expensive (from RUB 30,000) ❌ Difficult to find in stock ❌ May clog again with mileage >200 thousand km	30 000–50 000
Universal catalyst (For example, Bosch, Walker)	🔹 2-3 times cheaper than the original 🔹Easier to find in stores 🔹Can be customized by size	❌ Requires welding or adapters ❌ Cleaning quality is worse than the original ❌ May not pass eco-test	8 000–15 000
Flame arrestor + lambda probe blende	🔹 The most budget option (from RUB 3,000) 🔹 Does not reduce engine power 🔹 Does not require ECU firmware (with the correct setup)	❌ Not environmentally friendly (will not pass technical inspection with a gas analyzer) ❌ May increase exhaust noise ❌ Risk of lambda errors	3 000–10 000
Contract catalyst from disassembly	🔹 3–5 times cheaper than the new original 🔹 Keeps it environmentally friendly 🔹 Suitable for temporary solution	❌ Risk of buying a clogged or damaged copy ❌ Service life is unpredictable ❌ May require cleaning	5 000–12 000

In practice, most owners Almera Classic choose either universal catalyst (if the car is operated in the city and environmental friendliness is needed), or flame arrester with snag (if the car is over 10 years old and does not undergo age inspection). It is advisable to install the original catalyst only when warranty repairs or if the car is under warranty from an official dealer (which is unlikely for Almera Classic).

⚠️ Attention: If you decide to install a flame arrester, be sure to install mechanical or electronic snag of a lambda probe. Without it, the ECU will constantly record an error P0420, and the engine will go into emergency mode with increased fuel consumption.

Step-by-step instructions for replacing the catalyst with Nissan Almera Classic

Replacing a catalyst is a labor-intensive procedure that requires welding machine (if you install a universal catalyst or flame arrester) or special tool for unscrewing stuck nuts. If you are not confident in your abilities, it is better to entrust the work to professionals. However, if you have a hole and minimal skills, you can handle it yourself.

Screwdriver and wrenches 10, 12, 14|WD-40 or similar "liquid wrench"|New catalytic converter/flame arrestor|Exhaust system sealant (e.g. Abro)|Welding machine (if cutting is required)|Lambda probe decoy (when installing a flame arrester)|Gloves and safety glasses-->

Work order:

1. Preparation. Drive the car onto a pit or a lift, let the exhaust system cool (working on hot metal is dangerous!). Treat all threaded connections WD-40 and let sit for 10-15 minutes.
2. Removing the old catalyst. Unscrew the nuts securing the catalyst to the manifold and resonator (there are 4 of them). If the bolts do not budge, use impact wrench or cut them with a grinder. Carefully remove the part, being careful not to damage the lambda probes.
3. Installing a new element.
   • If you bet original or universal catalyst — align the holes and tighten the new bolts with the bushings (so that they do not unscrew due to vibration).
   • If you install flame arrester — weld it in place of the catalyst, having previously cut out the old body with a grinder. Don't forget to install the lambda probe blende!

Checking for leaks. Start the engine and check for blowing at joints. If necessary, apply heat-resistant sealant.

Reset errors. Connect the scanner and reset the ECU errors. If electronic deception is used, it may be necessary firmware for Euro-2.

It takes all the work 2–4 hours, depending on the condition of the thread and the need for welding. If you cut out the catalyst with a grinder, be sure to protect the fuel lines and wiring from sparks - wrap them asbestos sheet or a wet cloth.

What to do if the catalytic converter catches fire after removing it? Check Engine?

Removing the catalyst without additional modifications is guaranteed to lead to an error P0420 (“low catalyst efficiency”). This happens because the second lambda probe (installed after the catalyst) detects a lack of exhaust cleaning. The problem can be solved three ways:

• 🔧 Mechanical snag. It is installed instead of the second lambda probe and simulates the operation of the catalyst due to holes with ceramic chips. It is inexpensive (from 500 rubles), but may not work on new versions of the ECU.
• 📊 Electronic decoy (emulator). It connects to the lambda probe wires and corrects the signal, “deceiving” the ECU. More reliable than mechanical, but requires proper installation (from 1,500 rubles).
• 💻 ECU firmware for Euro-2. Disables control of the second lambda probe at the software level. The most reliable solution, but requires contacting specialists (from RUB 3,000).

On Nissan Almera Classic with motors QG15DE/QG16DE most often used mechanical snag, since the ECU of these cars is not very “smart” and is easily deceived. However, if after installing the fake the error does not disappear, you will have to install an electronic one or flash the control unit.

Important: if you removed the catalyst and did nothing with the lambda probe, the ECU will switch the engine to emergency mode, which will lead to:

• 🔥 Increased fuel consumption (up to +20%).
• 🐢 Limiting speed (no more than 3,000–3,500 rpm).
• 🚨 Constant burning Check Engine.

How to check if the trick works?

After installing the blende, reset the errors with the scanner and drive 50–100 km. If Check Engine does not light up again - the decoy is working. If the error returns, try a different type of cheat or flash the ECU.

How much does it cost to replace a catalytic converter? Nissan Almera Classic in 2026?

The cost of replacement depends on the chosen option (original, station wagon, flame arrester) and region. Below is the current price list for Moscow and Russian regions:

Service/Part	Moscow (RUB)	Regions (RUB)	Notes
Catalyst diagnostics (pressure check, scanner)	800–1 500	500–1 000	Often free for further repairs
Replacing the catalyst (work)	2 500–4 000	1 500–3 000	More expensive if welding is required
Original catalyst (20030-4M000)	35 000–50 000	30 000–45 000	Made to order, delivery time 1–3 weeks
Universal catalyst (Bosch, Walker)	8 000–15 000	7 000–12 000	Requires adjustment to size
Flame arrestor + blende	3 000–8 000	2 500–6 000	The price depends on the material (stainless steel is more expensive)
ECU firmware for Euro-2	3 000–5 000	2 000–4 000	Required when removing catalyst

Total minimum cost solving the problem (flame arrester + blende + work) will cost 5,000–10,000 rub., and maximum (original catalyst + replacement) - up to 50,000–60,000 rub. At the same time on cars older than 15 years, it is not economically feasible to install an original catalyst - it is cheaper and easier to remove it and flash the ECU.

If your budget is limited, consider purchasing contract catalyst from disassembly. Good specimens can be found for 5,000–10,000 rub., but before purchasing, be sure to check it for cracks and clogging (blow it with air).

FAQ: Frequently asked questions about the catalyst Nissan Almera Classic

Is it possible to drive without a catalyst if it doesn’t light up? Check Engine?

Technically it is possible, but it is fraught with consequences:

• 🔊 The exhaust noise will increase (the flame arrester does not dampen the sound as effectively as the catalyst).
• 🌍 The car will become “dirtier” - emissions CO And CH will grow 5–10 times.
• ⚠️ The risk of errors with the lambda probe remains (even if Check Engine does not light up now, it may light up later).

If you don’t care about the environment and noise, and there are no errors, you can drive. But for comfortable operation it is better to install a flame arrester with snag.

Which catalyst is better: original or universal?

The original catalyst is better in two respects:

• 🔹 Exact match by size and characteristics.
• 🔹 Durability (subject to quality fuel).

However, a universal catalyst (e.g. Bosch or Magnetti Marelli) is often not inferior in terms of resource, but costs 2–3 times less. The main thing is to choose a model with the same number of hundreds, like the original (for Almera Classic this is usually 400–600 meshes per inch).

What happens if you don't change a clogged catalyst?

Ignoring the problem will lead to:

• 🔥 Engine overheating (due to a violation of gas removal).
• 💥 Destruction of ceramics and the entry of its particles into the cylinders (risk of scuffing).
• ⛽ Increased fuel consumption by 15–30%.
• 🚗 Complete loss of power (the car will not be able to accelerate above 80–100 km/h).

In the worst case, you will have to do engine overhaul, which will cost 50,000–100,000 rubles.

Is it possible to clean the catalyst instead of replacing it?

Cleaning is possible, but effective only in early stage of congestion (for example, if the honeycombs are clogged with soot and not melted). Methods:

• 🧹 Washing with special chemicals (For example, Liqui Moly Pro-Line Katalysator-Reiniger).
• 🔥 Burning (heat the catalyst to 600°C with a gas burner, but this is dangerous!).
• 💦 Ultrasonic cleaning (in specialized services).

However, in practice, cleaning helps in less than 30% of cases, especially if the catalyst has already begun to deteriorate.

Is it necessary to flash the ECU after removing the catalyst?

Not required, but recommended. Without firmware, you will have to install a decoy lambda probe, which:

• 🔹 May fail over time.
• 🔹 Doesn’t always work correctly with the ECU Almera Classic.
• 🔹 Does not eliminate the risk of accidental errors.

Firmware for Euro 2 disables the control of the second lambda probe permanently, which eliminates problems with Check Engine.