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Last seen: 1 year 4 months ago
Joined: 01/10/2019 - 11:04
30-0300 FULL Lean - 2nd one!

So I bought a used 30-0300 from my local car forum and installed the kit on my car which worked great for a couple of weeks.   Then suddenly without warning I noticed on my comute into work the display went to 4 dashes and would randomly blip a brief 14.7 - 14.8 A/F ratio but then quickly go back to the full lean indicator.       I started troubleshooting the wiring, inspecting for any chaffing or bad grounds, etc.    I called Tech support and shipped my gauge in to have it checked.    I did the free Air Calibration and that showed my sensor PASS.         Having never gotten around this issue I assumed there must be some bad harness wire or something so I bought an entire brand new 30-0300 Kit and meticulously installed it, taking my time to ensure every wire was zip tied safely away from any heat, routing my harness into the car using gromets through the firewall, etc.   I even soldered all my power connections.         Lets just say I took a full day to do it absolutley perfect and the gauge worked without issue for about 2 weeks until today.    On my way to the office from lunch it went right back to 4 dashes and does the same thing.   A little brief flash of 14.7 or 14.8.    When I got to work I turned the car off..  Let it sit for a few mins.   Then let the sensor fully warm up before starting the car.      Usually when the car is not running it will show 4 dashes.   However this time it showed 14.7 so maybe it's sensing the fumes still lingering since I only shut it off a moment ago.     Started the engine and let it idle and the Gauge just shows 4 dashes FULL LEAN.  

I logged my car so that my tuner could have a look at the narrow band O2's data to confirm the fuel system wasn't experiencing any issues and after he read the log he said the tune is fine and it's something up with the gauge.   

1. Wiring is Perfect

2. Sensor is perfect

3. Gauge is secure perfect / wiring on back is plugge in good and tight

4.  Sensor screwed into Mid pipe where Secondary O2 sensor would normally be located.  

5.  No exhaust leaks whatsoever

6.  No intake leaks.


I find it hard to believe that 2 of these Kits would have the exact same issue.       Tech Support wasn't much help when I called them about this the first time.        Should I just give up on being able to use this product on my car?    I just dont' understand what is going with why it will work for several days and then just randomly go back to this.      


Last seen: 1 week 4 days ago
Joined: 06/07/2014 - 14:29
If you shipped a gauge in for

If you shipped a gauge in for testing, the repairs guys are pretty good at checking and finding problems. Did tech support ask you to send just the gauge, or did they ask you to send gauge plus the sensor and all the wiring?

Solder is not a good idea for tapping onto wires in an automotive environment. The heat from soldering makes the wire brittle, and the solder flux is corrosive also. Most people with automotive wiring experience will recommend to use crimps and splices, not solder. That said, problems in the power source wires usually end up with a gauge that seems to blink or 'reset' instead of powering on and acting like normal and it sounds like your problem is different. 


If you think you're seeing an always-lean reading that is likely the sensor itself, or the wiring between the gauge and the sensor, and it could also be the gauge itself. Do the brake-cleaner-on-rag test, as described here: https://www.youtube.com/watch?v=rmnxKLjM25g   Unfortunately that video doesn't include troubleshooting tips, but that's probably because most troubleshooting involves swapping in known-good parts. If your gauge never shows rich when the sensor is exposed to the rag with brake cleaner fumes, try replacing the sensor or the harness between the gauge and the sensor. Your post says you bought a second gauge so you should have spare pieces to swap out.


Waiting for the sensor to get warm before starting the engine can be a bad idea. When you first start the engine there may be has lots of unburned fuel or condensed water droplets in the exhaust, which can crack the ceramic sensing element of the sensor if it's already fully warmed up.


Hope that helps,


Last seen: 1 year 1 month ago
Joined: 03/31/2019 - 12:14
I have the same problem, my

I have the same problem, my expensive sensors keeps dying. Would it be beneficial to install the controller to a separeate switch, that could allow then engine to run for a minute or two, before starting controller and heating?