Bosch vs Denso Oxygen & A/F Sensors: Review

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Alright, let’s talk about oxygen sensors. If your stock o2 sensor went kaput, there’s a 90% chance you’ll be looking at Bosch or Denso as replacements.

The obvious question is…which one’s actually better?

I have two very simple rules of thumb here.

First rule: If you drive an Asian car – and especially Japanese brands like Honda or Toyota, go for Denso (here are Denso’s top sellers). A lot of Asian-made vehicles come with Denso as OEM, actually.

Bosch oxygen sensors are a better fit for European vehicles. The brand’s sensors are also thicker, “fatter” than other aftermarket manufacturers.

In many cases, they are also cheaper. If you prefer that, check some Bosch alternatives.

Second rule: Never, ever get Bosch’s Universal lambda sensors.

No, seriously! They’re longer than OEMs so you can’t really use any sensor tools. Also, the procedure around getting the wiring harness to connect is the stupidest thing ever.

I’ve seen a lot of people complain about these both on forums and on product pages (here’s an example).

Go for the Premium o2 sensors instead. They’re not too expensive, yet a significant improvement in terms of fit and ease of installation.

With that said, I’m of the opinion that overall, Denso manufactures better aftermarket parts. Where Bosch lasts for 50k miles, Denso’s superior design ensures the sensor stays with your car for a longer time.

Here’s the reason: 

Denso o2 sensors review: A difference from Bosch oxygen sensors

The key is #5, which is the aluminum oxide trap layer. It prevents silicone, lead and other unwanted fellas from entering, keeping the platinum electrode intact for longer.

Cool, right?

A fun fact: Bosch made electronic fuel injection cost-effective, after getting the oxygen sensor from Bendix. However, Denso is the one who introduced A/F sensors on the modern market.

And to this day, they’re still the best option for A/F sensors.

If you’re on a budget, though? You can still go with Bosch as an alternative in the o2 department. Let’s summarize these before a more in-depth review of Bosch and Denso oxygen sensors.

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Denso oxygen sensor
  • Better layered, advanced protection design.
  • The better OEM replacement for Honda, Toyota etc.
  • Improved longevity compared to Bosch.
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Bosch o2 sensor
  • Decent performance on a lucrative price.
  • Pre-coated threads for easier installation.
  • Laser-welded stainless steel construction keeps things clean.
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Denso A/F sensor
  • The king of wideband sensors with improved ratio coverage.
  • Zirconia allows for maximum accuracy.
  • Probably the easiest to install A/F sensors on the market.
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Bosch vs Denso oxygen sensors:
What are the most important differences?

Obviously, the first one is the price, with Denso parts being way more expensive. I outlined the reason above.

However, there’s also another small difference.

Denso offer only one type of oxygen and A/F sensors. Bosch also stick to only one type of A/F parts, but they divide their Lambda sensors in two types: Premium and Universal.

As I pointed out, universal ones can be a real mess. While their name implies ease of use, I’ve read enough horror cases from car owners who recommending steering away from them.

No, seriously – take a look at this video, how confusing it is, and then read the comments from people as flabbergasted as me:

Bosch might have contributed to making electronic fuel injection practical…But I just don’t know what were they thinking with this. It’s the furthest thing from practicality.

Denso oxygen & Air/Fuel sensors review

Here’s how a typical Denso o2 sensor looks like on the surface. This one is the #234-4668 replacement part for GMC Yukon, Chevy Silverado etc.

Bosch vs Denso oxygen sensors: Which one is actually better?

What matters is the things happening under the hood, though. Let’s take a look.

Similar to Bosch and other quality aftermarket brands, you have a laser weld at (1). Usually it’s not done by hand, rather by a factory robot. (2) is where things get important – this is a porous PTFE filter that allows oxygen to enter without letting in any liquid (water) or contaminants.

Other features include:

  • Stainless-steel body that’s corrosion resistant

  • Refined zirconia elements that improve how responsible your o2 sensor is

  • Full smog-test compliance

Denso sensors – both A/F and o2, are ridiculously easy to install. They’re manufactured to be as close to OEM parts as possible.

Speaking of Air/Fuel parts – or wideband oxygen sensors, as they’re also known as…Here’s how the Denso ones look like (#234-9001 for Toyota Tacoma as an example):

A/F sensors: Denso or Bosch? For Toyota, there is a clear winner...

Generally, they follow the same construction fundamentals as their o2 brothers.

One additional thing to keep in mind with them is the A/F ratio they can measure. In the case of Denso, their wideband sensors measure ratios from 12:1 to 19:1.

This little guy here can save you if you’re suffering through the dreaded P1135 error code for bank 1, sensor 1 in the air/fuel sensor heater circuit.

Here’s a good video on installing one:

Bosch lambda sensors review

So how do Bosch’s aftermarket parts fare?

Pretty decent. The manufacture here is also on point, even though considering the lower price you don’t get all the bells and whistles of Denso. This is actually similar to how these two brands approach their spark plugs too.

Here’s a typical lambda sensor from Bosch (the popular #15717 for Ford, Mazda and others):

Bosch o2 sensor review: A decent, cheap alternative to higher-end Denso

The Premium line consists of thimble and planar switching sensors, behaving similarly to stock parts. You get:

  • Laser-welded (double) stainless steel body

  • Seared protection tube

  • Threads that are pre-coated with anti-seize compound

The body is durable enough, and the overall design of these fellas also makes sure no contaminants enter inside. The additional Denso layer isn’t here, which impacts the overall longevity of the lambda sensor, however.

Unlike the universal line, the premium o2s are very easy to install. The coated threads definitely help with that, so even if you’re not a DIY master you should be able to deal with these.

Bosch or Denso A/F and o2 sensors:
What is your experience?

There’s a high chance that your vehicle came with either of these as OEMs. Or maybe you went with one of the two brands as a replacement, but it didn’t work out. Or maybe it did.

What are your impressions on these two brands’ aftermarket lambda parts?

Let me know in the comments below. No joke, I read everything and try to reply asap. 🙂

For more info, you can always visit both Denso’s official site or the official site of Bosch. Speaking of the latter, I also have a review of Bosch’s braking system. Head over there if you’re curious about stuff like brake pads and rotors.

Founder of ToolingFun. Couldn't even change a lightbulb in my teenage years. Discovered the joy of DIY projects during my 2nd year in college. All about tinkering around, trying fun tools and projects, and giving my opinion on industry brands!