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AEM Wideband Failsafe Gauge - Proving Grounds

Preventing engine failure one smart gauge at a time

May 21, 2013
Modp 1304 01 o+aem wideband failsafe gauge+1995 nissan 240SX Photo 1/6   |   AEM Wideband Failsafe Gauge - Proving Grounds

Test Mule

'95 Nissan 240SX

SR20DET Turbocharged 4-cylinder
Relevant Mods

Key Features

  • Protects your engine by constantly monitoring AFR curves and activating a user-defined fail-safe strategy if it runs lean
  • Can display boost or vacuum and AFR or lambda simultaneously on the same gauge
  • Built-in internal boost sensor ensures accurate boost level display
  • Includes Bosch Wideband UEGO sensor and weld-in bung
  • Three-plus hours of data-logging capability
  • Full-color organic light-emitting diode (OLED) display in center and 24 three-color sweeping LEDs
  • Data analysis software can show AFR, RPM, boost, alarm, and others


Measuring an engine's air/fuel ratio is arguably the best method of understanding how well or poorly an engine is running. Not that long ago, it was very expensive and cumbersome to install an AFR device into a car. In most cases, AFR was accurately determined on the dyno during tuning, and that was it. Fast-forward to today and there are many compact and inexpensive solutions to monitor AFR every time you start your engine.

Modp 1304 02 o+aem wideband failsafe gauge+kit Photo 2/6   |   With everything included for a quick and relatively easy installation, AEM’s Wideband Failsafe Gauge will be up and running in no time.

AEM was one of the first companies to market with a wide-band A/F gauge, and it has continued to develop the product. The newest iteration and arguably the most advanced is the Wideband Failsafe Gauge, and it's much more than just a wide-band gauge. At the heart of the system is an electronic controller that, when provided with the proper inputs such as boost/vacuum and AFR, can trigger a user-defined output that can be as simple as a warning light or can activate a safety sequence that will bleed boost from a wastegate or pull timing. It's an incredibly powerful and intuitive tool that can be as simple or advanced as the user desires.

Utilizing a 270-degree, 24-color sweeping LED display and a full-color organic LED (OLED) center-mounted digital panel, the Wideband Failsafe Gauge can display either boost/vacuum or AFR in the desired locations.

Using the Failsafe software, one can configure the display options, including LED colors, max/min AFR, and boost levels. Spend some time setting up and familiarizing yourself with the AFR versus Boost window and you'll be rewarded with a fail-safe setup that will intervene if conditions falter outside the set parameters.

If that weren't enough, the Failsafe Gauge is also capable of data-logging more than three hours worth of user-defined parameters that can be downloaded to a PC laptop through the gauge's built-in USB connection.


Our Nissan S14 project car has an AEM EMS installed in it, so for reference's sake, our installation was a little bit different from one with a stock ECU or piggyback EMS. We wired it directly to the EMS to activate cut boost pressure in the event of an alarm. In the case of a turbocharged car with stock a ECU and electronic boost control, we would suggest wiring it into the solenoid to trigger a release of boost pressure. If you're running a manual boost controller, then it's time for an upgrade. Otherwise a warning light trigger may be the best option. (Note: The Failsafe Gauge will flash red on its OLED display if an alarm is triggered, so it may be redundant unless the gauge is tucked away from eye level.)

Modp 1304 03 o+aem wideband failsafe gauge+face Photo 3/6   |   An assortment of different gauge faces come with the Failsafe, enabling you to choose between a variety of boost/vacuum and AFR display options.

Setting up the software is easy, and AEM did a great job on the instructions, so as long as you read them carefully and follow along, you should be able to set up the Failsafe tuning with relative ease and configure the gauge display to your desired settings.

Ideally, you want access to a dyno to set the upper and lower AFR limits in the software. However, a long stretch of road will suffice, and after several pulls, the auto-set-limits function had plotted a fairly accurate chart as to what was considered safe and not.

AEM has integrated an alarm delay configuration to prevent false alarms. For example, in some cases, a quick shift can cause a quick lean spike in AFR, so to avoid an alarm trigger setting off, the user can define a time delay of say, 500 milliseconds, and avoid a false trigger.

The Wideband Failsafe Gauge has proven to be a very valuable and a powerful tool in a compact package. Aside from the obvious benefits of having AFR and boost readings available all the time, the rest of the features like data-logging and fail-safe trigger make this a must-have on any performance car. Long gone are the days of worrying about unexpected engine failures. There are no excuses anymore.


AEM Electronics
Hawthorne, CA 90250



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