How To Install a AEM Failsafe UEGO

How To Install a AEM Failsafe UEGO


AEM Electronics has been at the forefront of wideband performance since their very first AEM UEGO gauge. If you own the original gauge, take a look here at our How To for further installation instructions on a Honda Fit. And as great as the original is, we absolutely love the new AEM Failsafe UEGO Wideband Gauge.

Delivering the same level of excellence and accuracy found in the earlier models, the new wideband takes Air/Fuel monitoring to the next level. AEM takes the UEGO and delivers a new experience and features like displaying boost as well as A/F ratio or Lambda at the same time.

The new display is bright and looks extremely cool with a OLED screen that helps you see what exactly is going on. Similar to the older UEGO gauges, the new Failsafe has 24 three color sweeping LED’s that let you know what your A/F is exactly.

But the new Failsafe UEGO is more than just a gauge, the Failsafe UEGO allows you to dictate actions based on lean or rich conditions. Using AEM’s programmable software, you can dictate what actions need to be taken if your vehicle’s A/F slips or rises to a value that’s programmable by you. The Part number for this Failsafe UEGO is 30-4900and it’s easily one of the biggest must have mods for any forced fed vehicle.

We’ll be installing the new AEM Failsafe UEGO in a 2003 Honda Civic Si EP3 today with a Treadstone turbocharger kit, putting down 324 whp on our Dynojet 448X. Please let us know if you have any questions about our How To Install a AEM Failsafe UEGO article in the comment section below.


To install the Failsafe UEGO gauge, we need to weld an additional oxygen sensor bung downstream of the turbocharger. Because of the engine orientation of the K20, instead of the 02 housing we’ll be installing this UEGO in the downpipe.


The new Failsafe gauge connects by way of 2 flying looms, which are plugged into the back of the gauge shown below.


There’s also a vacuum line for boost source as well as the flying loom with secure connectors for the Bosch oxygen sensor. Take the flying loom for the Bosch wideband as well as the vacuum line and run both into your engine bay. We used the EP3 body plug thats near the gas pedal.

There is an easy to spot blue wire/tube going through that spot as well making the location easy to identify. The line will come into the cabin above and slightly right of the gas pedal.


Once you have the lines run to the engine bay, tee the boost vacuum line to your intake manifold. You can either cut and tee into the fuel pressure regulator vacuum line or tee into another existing source.


With your vacuum or boost reference teed into the intake manifold, you must now lower the downpipe in order to cut and weld the new bung in place.

Raise your Civic Si on jackstands and secure the vehicle if you do not have access to an automotive lift. Begin by undoing the catalytic converter inlet bolts.


When your catalytic converter inlet bolts are removed, you can take out the two bolts that hold the downpipe to the turbo 02 housing. This setup may vary depending on your turbocharger kit, but this turbo kit bolts back up in the stock location.


With the downpipe removed, drill a hole and weld the oxygen bung that supplied by AEM in place.



Once you’ve got the Bosch wideband installed you are now clear to connect the wiring loom from the gauge to the sensor. Make sure to secure the UEGO connection by snapping down on the clip shown below.


Now you’ve got just a few wires left to connect for our How To Install a AEM Failsafe UEGO Guide. Connect the black wire to the negative terminal of your Civic battery, and then the red wire to the switched power source at the ignition column. We’ve included a wiring pinout for the AEM UEGO Bosch sensor, in case you want to wire it yourself.




Go inside the cabin and take apart your Honda Civic SI steering column cover, which will require you to remove four screws.


Once the Civic steering column cover has been removed, you can access the ignition plug harness. There’s a brown connecting harness that can be accessed near the back of the steering column itself.

You are looking for a brown five pin harness that leads to the ignition switch. This is the harness you will be taking switched power from for your Failsafe UEGO gauge.



Take the red wire and connect it to the white wire with red stripe coming off your brown ignition plug. This wire is a switched power source that turns on when the key is set to the “ON” position. Once you have connected the black and red wires, test your UEGO by turning the key to the “ON” position. The Failsafe UEGO gauge should light up and commence it’s Power On Self Test.

You are nearing the end of our How To Install a AEM Failsafe UEGO article, the next step is to program your Failsafe to operate like you want it to.


The rest of the wires in the AEM Failsafe UEGO gauge are for output purposes only, please click here for AEM Infinity and AEM EMS wiring questions. We’ll also include a complete pinout for the Bosch UEGO flying loom, which is a 16 pin connector.


  1. Black Ground; connect to good chassis ground or directly to battery negative (−) terminal
  2. Red Ignition power; connect to a fused key on +12V power source
  3. Black USB – Dedicated
  4. N/C Reserved
  5. Red USB – Dedicated
  6. Green USB – Dedicated
  7. Blue *OPTIONAL* Ground output; connect to an external auxiliary device (1.5A max current)
  8. White USB – Dedicated
  9. Green *OPTIONAL* Engine Speed Input; connect to a square wave trigger
  10. Gray *OPTIONAL* Gauge backlighting; connect to instrument lighting dimmer wire
  11. N/C Reserved
  12. N/C** *OPTIONAL* AEMnet –
  13. N/C** *OPTIONAL* AEMnet +
  14. Brown *OPTIONAL* Analog ground for AFR and MAP; connect to sensor ground of data logger or EMS
  15. White *OPTIONAL* 0-5V analog output for AFR; connect to + analog input of data logger or EMS
  16. Yellow *OPTIONAL* 0-5V analog output for MAP; connect + analog input of data logger or EMS

Once your Failsafe UEGO is wired in and installed, take some time to load the software on a laptop of your choice. For more information on loading the software, refer to AEM’s website at :

Once you have your software installed, it’s time to update it’s firmware before you go any further or connect it to you Failsafe UEGO. While connected to the gauge with the USB cable, open the AEM Wideband Failsafe Software. Go to the Tools drop down menu and select Update Firmware and follow the on-screen instructions.

You can also program your UEGO before installing it into your vehicle, but there’s not going to be much to adjust as the internal MAP sensor or UEGO input is not connected.

Congratulations you have now completed our How To Install a AEM Failsafe UEGO Guide, please check out our How To Program your AEM Failsafe UEGO gauge article as well.

Have any questions about this guide? leave us a comment below and let us know!