O2 Sensor Analyzer Review A Product of Lenehan Research


Staff member
Nov 13, 2006
O2 Sensor Analyzer

Product review of Lenehan Research's
O2 Sensor Analyzer
by: Bruce Bonebrake
Managing Editor at BAT AUTO

PHONE: 1-949-472-1026

When Peter Lenehan from Lenehan Research contacted us about his newest product, the O2 Sensor Analyzer ,
needless to say, I couldn't wait to get my hands on it. This tool is very unique in a lot of respects.
To be able to determine 100% (+ /- 5%) that the O2 sensor is performing properly is a hard task to accomplish. With a Scan Tool connected, or a DVOM, you may see the voltage fluctuation and think that the O2 sensor is fine, BUT is it really? Even with an expensive Lab Scope, you may be fooled into an incorrect diagnoisis. Let me tell you why. The Lab Scope, DVOM and Scan Tool are merely reading the O2 sensor during the current engine performance cycle. The only one of the three testers that reads the O2 in "Real Time" is the Lab Scope. The question is, what about the reponse of the O2 sensor under the extreme operating conditions the system will be performing in, while driving the vehicle daily? Wouldn't this be the most important time for the O2 sensor to send the correct voltage signal (input signal) to the PCM? You bet it is!!
The O2 sensor Monitor will do JUST that!! When the O2 sensor Test is selected, the first thing that will happen is the O2 Sensor Analyzer will force the system below 175 mV (full Lean). Once this has been accomplished, the "Snap Throttle" / "Introduce Propane" LED on the tester, will illuminate after the Start button is pressed. After the throttle has been snapped (or propane is introduced), the O2 Analyzer will check to determine if the O2 sensor went to over 800 mV(full Rich) within 100 mS. If the O2 Sensor DID make the response, the "PASS" LED will illuminate. If the O2 sensor DID NOT make the required response, the "FAIL" LED will illuminate.
The first question that may come to mind right now is, why do we need to know this? If the Scan Tool shows an "active"O2 sensor, doesn't that tell us that it is working properly? That is the problem, no, IT DOESN'T!!
Let's get started.. I'll explain more along the way.

It is said that one out of ten vehicles on the road have a defective O2 sensor. The O2 Sensor Analyzer will find that one vehicle, and also, let you know without a doubt that the other nine are OK. I believe that the heart of the fuel management is the O2 sensor. The PCM is the brain, naturally, but the PCM is making decisions based on the input information from all the sensors. The sensors that are "borderline" are the ones that are extremely hard to find. With the MULTIPLE O2 sensors on today's vehicles, it would be easy to spend HUNDREDS of dollars on a SINGLE O2 sensor. That is right, some of the O2 sensors are very expensive, and, how do you know that the O2 sensor is bad and should be replaced? OR that the new sensor you replaced the old one with is operating properly? I realize that it is brand new, but how many times have we seen a part that was new, be defective? It is not common, but the fact remains, it happens. So, let's review what we have talked about so far.
1) It is VERY DIFFICULT to be absolutely certain that the O2 Sensor(s) are working 100%, even with a Lab Scope.
2) It is said that one out of ten vehicles will have a defective O2 sensor.
3) The "heart" of the fuel management is the input sent to the PCM from the the O2 Sensor(s)
4) Some of the O2 Sensors are VERY EXPENSIVE, and then on a "multiple O2 Sensors" equipped vehicle, which O2 Sensor do you replace? And, are you 100% certain that it is the right one and not that something else in the system is causing the O2 Sensor to stay LEAN or RICH?
5) The State of California has an O2 Sensor test as part of the vehicle emission test (CA BAR). If you perform repair work in California, or if your state adopts this, and a vehicle fails the O2 Sensor test, how will you verify that the replacement O2 Sensor will be working properly?
Makes us think, doesn't it? Ok, ok...(grin)..Let's get to the review..

Let's start with the packaging. You know, when I buy a piece of equipment, maybe it is just me, but the package that will hold my investment tells me that the manufacturer cares about the product. The last thing I want to do is damage my investment and I want to be able to completely and securely store it after use. Let's take a look at the package that the O2 Sensor Analyzer comes in. It is a heavy duty blow molded case that fits the tester like a glove!! Right from the start, I am impressed when I see this. And, have you ever had to hunt down the contact number of the product? Well, Peter has the phone number ON THE LABEL, ON THE INSTRUCTION BOOKLET, and the LABEL LOCATED INSIDE THE TOP COVER!!
When you open the blow molded case, here is what you will see on the inside of the cover. These are the operating instructions folks!! VERY HANDY!!! There is also the enclosed manual that will provide additional information, but, this label explains how to connect the leads and how to use the functions. See the phone number and even the website address? No need to search for the information here.. Yes Peter, (grin).. we DO notice these things, and they are MUCH appreciated!!!!!

The tester is enclosed in a reuseable "bubble wrap" pouch for safe keeping. You will notice that with the contents removed, as seen in the lower picture, there is even a foam mat in the bottom of the case. This is what I am talking about. You know, to see the tester at this stage, let's face it, you have already purchased it, it has arrived to you, you open the shipping box and have removed the carefully placed shipping material, the blow molded case, and as you keep opening and removing pieces, all the way to the end, the care has been thought of and given here. What does that tell you? It tells me what I already know from reviewing other Lenehan products, to Peter, this is personal. This isn't a company that "mass-produces" a product to get rich quick, Peter takes great pride in his products!!

The contents of the blow molded case are:

1) the O2 Sensor Analyzer itself
2) the user's manual
3) the warranty card
4) the reuseable bubble pouch
5) a zip bag containing the lead adapters
6) a copy of the Motor's Top 20 Tools article that Lenehan Research was awarded for the superb "What Quit's First" tester.

Getting started...
The tester will need 2-AA batteries installed. They do not come with the tester, which is just as well, as the shelf life of included batteries would be unknown if they did.
Inserting the batteries is a simple "no tools required" task. The rear of the tester has a slide open battery cover. The polarity is clearly marked inside the battery compartment.


Staff member
Nov 13, 2006

The required connections will be three wires. The lead coming out of the tester is secured to the tester with a nylon locking device. The main lead is an 18 gauge Teflon cable.
The lead from the exit point at the bottom of the tester to the end of the three leads on the other end, I measured it to be exactly 70" long. Plently of lead to reach the "under vehicle" O2 sensors.
The three leads: the Black wire will be attached to a GOOD engine ground. The end of the Black wire is equipped with an alligator clip to make the ground connection. The Red and White wires will attach to the O2 Sensor harness. The tester comes with the adapter leads for both connections. The adapter leads are bundles with a choice of three harness terminal designs. You would want to determine which terminal of the adapters to use by disconnecting the O2 sensor and matching the adapters to the terminals on both sides of the disconnected O2 sensor plug.
Once the needed terminal is known, attach the adapters to the red and white leads coming from the tester. You will want to tape the unneeded terminals of the adapters so an accidental connection to each other or ground doesn't result. With our adapters attached to the leads, we are ready to connect the tester to the vehicle.

Our test vehicle is a 1994 S10 Blazer, 4.3 VIN W, 4WD. This application is equipped with a "three wire" O2 sensor. The O2 sensor is mounted just past the "Y" connection in the exhaust pipe that is routed along side the right (passenger's) side transmission. It is difficult to get a good picture of the sensor, due to its location, but the top picture is of the sensor body. It would have been easier to do the review on a 1 wire exhaust manifold sensor, located under the hood, but more and more, the O2 sensors are under the vehicle. The three wires from the O2 sensor harness have a disconnect plug located mid way up, and it is secured with a wire tie to the transmission dipstick tube.
The three wires are as follows:

PINK.........O2 Sensor Heater....+
BLACK....O2 Sensor Heater.....-
PURPLE...O2 Sensor Signal to the PCM

With the tester's lead adapters connected to the the O2 sensor's PURPLE wire (the WHITE adapter connected to the PCM side of the plug ...the RED adapter connected to the O2 sensor side of the plug). Even though the lead from the tester has a Teflon heat resistant covering, I would advise taking the time, as shown in the middle and bottom pictures, to wire tie the harness away from the exhaust system. Also, if connecting the tester under the hood, be careful to secure the connections and the cable away from any moving parts.

Using the tester is very simple. There are seven touch sensitive buttons on the face of the tester. The tester has four operating modes:

(MODE 1) O2 MON (Monitor)

The operating status of the O2 sensor in "Real Time", displayed by way of 10 SUPER BRIGHT LED's. The top LED (RICH) is "full rich"(800mV). The bottom LED (LEAN) is "full lean"(175mV). The center is the 14.7-1 air/fuel mixture. The 10 LED's are arranged in a slight "S" shape pattern, and when the O2 sensor is in "closed loop" as shown in the lower picture, the LED's will light up in a "snake" type fashion. To really appreciate an active O2 sensor, it would take more than a snapshot. The operating O2 sensor puts on quite a "light show" with the LED's constantly on the move.
The top picture is showing what an "open loop" (cold) O2 sensor will display. Even with the heater circuit disconnected during the review, in about 2 minutes, the O2 sensor was responding very well, as shown in the lower picture.
At this point, we are just observing the O2 sensor in operation.
To operate the tester in this mode, the MODE/START and O2 MON buttons are pressed together.


Staff member
Nov 13, 2006

(MODE 2) O2 SIM (Simulator)

This is a nice feature!! Since the tester is connected "in-between" the O2 sensor and the PCM, the O2 MON can send a Lean or Rich signal to the PCM. The PCM will respond, and by watching the LED's we can determine if the computer system is operating correctly. This test will tell us if the O2 sensor follows the input given to the PCM and will go full range (all the way Rich and then Lean). In the next test, the system must be able to go full Lean in order to perform the tester's Mode 3, the O2 Test.
The O2 SIM is very handy for checking the way the PCM reacts to the simulated commands. A fault connection at the PCM or a defective PCM will be evident if the simulated signal makes no change. By now, during the O2 MON mode, we will already have seen whether or not the O2 sensor is functioning. This test will be useful and quicky determine if there is a "command/response" fault within the system.
And with the O2 MON test, we already know that the vehicle's system is capable of making a change and the change was received by the O2 sensor.
To operate the tester in this mode, the MODE/START and O2 SIM buttons are depressed together.


When the buttons are depressed, and the O2 TEST LED is illuminated, the tester will send a 950mV (GO LEAN) signal to the PCM. As shown in the top picture, I depressed the buttons for the O2 TEST mode when the LED was at the full RICH position while it was in the Mode 2 (O2 SIM) test mode.
In a matter of seconds, the tester's LEAN LED illuminated. When the LEAN LED is illuminated, press the MODE/START button one time, and the SNAP THROTTLE OR PROPANE LED will light up.
At this time, snap the accelerator, and the fuel enrichment that would be normally supplied by the PCM under this condition should change the LEAN (175 mV) LED starting point to RICH (800 mV) in less than 100 mS. If it does, the PASS LED will illuminate. If it does not, the FAIL LED will illuminate. Perform the test a couple of times to prove positive that the O2 sensor is either good or bad. If the test should fail again when the test is repeated, introduce a quick blast of propane into the air cleaner when the SNAP THROTTLE OR PROPANE LED is illuminated. If the O2 sensor should fail again, you have determined 100% (+/- 5%) that the sensor is faulty.
A couple of points to keep in mind, on a V-6 / V-8 application using seperate O2 sensors for each bank of the exhaust output stream, there is a slightly different technique to follow as the PCM will recognize the forcing of one O2 sensor lean, and ignore it, and set a code. Also, the heated O2 sensors, when the O2 sensor connector is unplugged, and if you leave the heater circuit disconnected, this could set a DTC (Diagnostic Trouble Code) indicating the O2 Heater circuit is faulty. With the heater circuit unplugged, naturally the O2 heater is not going to function. If the O2 sensor does not seem to be working as you would note during MODE 1 (O2 MON), you can easily release the terminals from both sides of the O2 harness, and connect the wires/terminals for the O2 sensor heater to each corresponding terminal outside the O2 sensor plug assembly.
I have been reviewing/testing this product for about 4 months now. I have kept track of the vehicles that were tested and I never had a problem with the O2 sensor not fully warming up or causing the "Check Engine" light to turn on. What I would do is connect the tester while monitoring the coolant/engine temperature and the ten O2 sensor LEDS, and perform MODE 2 (O2 SIM) and the MODE 3 (O2 TEST) after the engine is fully warmed up. The O2 sensor seems to be located close enough to the outgoing exhaust stream to pre-heat the O2 sensor enough to correctly operate. This might be a problem the farther away the O2 sensor is located from the outgoing exhaust stream. This procedure and the in-depth MODE descriptions are located in the easy to read users guide. Also, on a four wire O2 sensor system, where the sensor ground is through the four wire connector, Peter included in the tester contents a neat ground wire terminal assembly where you can attach the ground circuit from both sides of the O2 sensor plug.
I have connected the tester to sixteen vehicles, and out of the sixteen, three failed the O2 TEST. One of these vehicles is MINE. I have a 1987 Chevrolet ElCamino with a 5.0L VIN H Feedback carburetor system, and the O2 sensor tester indicated a repeated O2 sensor failure, even with the propane enrichment used instead of the Snap Throttle technique. This car is rarely driven, so even though this was a surprise to me as the O2 sensor is fairly new, I was glad to find that the O2 sensor was defective. And YES, I did verify the repair. I retested the OEM replacement O2 sensor, and the new O2 sensor did PASS...EXCELLENT!! OH, and by the way, if you do the math on the vehicles tested during this review, the failure rate, it equals out to a 18.75% failure rate. That is almost double the suspected 10% of defective O2 sensors on the road!!!

To enter the O2 Test Mode,
press the MODE-START button and at the same time, press the O2 TEST button.
Once the LEAN LED illuminates,
press the MODE-START button once and the SNAP THROTTLE OR PROPANE LED will illuminate.

Mode four is simply turning the tester off. Press the MODE/START and OFF buttons and the tester will shut off.

Time to rate this tester, the O2 Sensor Analyzer from Lenehan Research.
This tester rated by Bruce Bonebrake 5-2002

Product Design...................EXCELLENT! Great attention to every detail throughout the system, starting with the packaging!!!!
Product Usefullness...........Designed for the professional Technician, and it would be a "must have" to accurately test/diagnosis the O2 sensor(s)!!
Product Ease of Use/Accuracy.......Simple to connect and use. The tester gave a correct and consistant diagnosis of the O2 sensors tested!!
Product Support...................Support information located in several locations!! Including the phone number and website address!! The Lenehan Research website is nicely designed and very easy to navigate!!
Product Instructions For Use....The Quick Hook Up and Users Guide is affixed to inside cover of the protective blow molded case and also a detailed Users Guide is included..
Product Updates................NONE REQUIRED!!!!
Product Lead Design.........Six foot long lead for easy use inside the vehicle or in the engine bay. The lead assembly is a Teflon cable containing three 18 gauge Teflon wires to ensure years of reliable service...VERY NICE!!
Product Warranty............1 Year warranty provided!!!
Product Price....................ONLY a MSRP of $399.99 (USD)
Product Ordering..............By contacting Lenehan Research and locating the nearest reseller near you.

"Thank you for reading my review!! If you have any comments, please let us know!! Your feedback is very valuable to us!!"
Bruce Bonebrake
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Bruce Bonebrake