This page is for professional service technicians as a forum for the exchange of ideas and information in regards to OTC tools and equipment. If you have any questions regarding the application of any OTC product, you can e-mail us at tech@otctools.com. Be sure to include a phone number where you can be contacted! You can also call us at 1-800-533-6127, or fax us at 1-800-955-8329.

MicroGas Free BBS Update Instructions
OTC's MicroGas brought you breakthrough technology just a few short months ago. Now, we've added even more features and enhancements to make the MicroGas an even better tool. Here's what's included in the FREE update:

Maintenance Schedule
Specially designed to help you track the time intervals between maintenance procedures on your MicroGas. The menu selection is located under the "Customer Service Menu," and tracks items such as calibration, pump replacement, and sample cell cleaning intervals. As the maintenance time limits are reached, the MicroGas will automatically prompt you on the next power-up that maintenance is recommended.

Zero Detection
Protects the MicroGas from receiving an inaccurate zeroing procedure. If you don't remove the exhaust probe from the tailpipe during a zeroing procedure, the MicroGas will tell you to redo the test.

Zero Counter
Displays the time remaining before the next zeroing procedure is required. Now you'll know if there is enough time to perform a diagnosis before having to re-zero the MicroGas.

Stand-by Mode
If you leave the unit running for extended periods of time, the MicroGas automatically goes into the "stand-by mode."

System Performance
The performance of the MicroGas has been enhanced, resulting in smoother operation and more descriptive messages that allow you to operate the unit more efficiently.

Download Procedures
There are two versions of code that must be downloaded: the application code and the bench code. Be sure an analog phone line is being used. DO NOT use a digital phone line.

Connecting the MicroGas and Modem
1. Connect the MicroGas to the modem (#236405) using the download cable (#236403).
-DB-9 cable end (female) to the top, right, male connector on the MicroGas.
-Connect the DB-25 cable end (male) to the female connector on the back of the modem.
2. Remove the phone cord from the phone, and plug it into the "line" jack on the back of the modem.
3. Using the cord supplied in the modem kit, connect your phone to the modem's "phone" jack.
4. Connect the power adapter to the modem and turn it on. You'll find the on/off switch on the back of the modem. Be sure the LEDs light up on the modem's front panel.

Downloading the Application Code
1. Power up the MicroGas, and go to the gas analyzer "Main Menu."
2. Select "Reprogram Utilities."
3. Read "Warning" and "Attention" screens, then proceed to the next menu item.
4. Select "Download Configuration," and verify that the information appears correct, then exit.
5. Select "Reprogram Gas Application."
6. Download the 14 digit application code certificate number: A2000000001732.
7. Allow the unit to complete the download procedure.
8. Cycle the power to return to the "Main Menu."

Downloading the Bench Code
9. Select "Reprogram Utilities" from the "Main Menu."
10. Again, read the "Warning" and "Attention" screens, then proceed to the next menu item.
11. At the "Reprogram Utilities" menu, press the following "hot keys" simultaneously: F1, F2, and Exit.
12. The screen now displays "Reprogram Gas Bench." Verify before proceeding.
13. Download the14 digit bench code certificate number: B200000000635B.
14. Allow the unit to complete the download procedure.
15. Cycle the power to return to the "Main Menu."
16. Select the "Customer Service Menu, then "System Revision." The "Software Revision" should now be "16," and the "Version" should be "D."
17. Calibrate the unit upon completion of the download.

If you have any problems or questions, refer to the MicroGas instruction manual, or contact OTC Technical Services at 1-800-533-6127.

MicroGas Date and Time Change
The date and time information programmed into every No. 3718 and No. 3732 MicroGas Analyzer manufactured before March 1, 1999 must be changed. Here is what the screen will look like when the unit is first powered up:

Initializing Gas
Monitor
Please Wait

Maximum Time Remaining (if a time value is displayed here, no date and time change is necessary. If a time value is not displayed here, use the following procedure).

Wait for Initialization
or Press
F1 to Enter Gas Demonstration

Step 1: At the initiation screen, press F1 for Demo Mode.
Step 2: Select System Configuration Mode; press ENTER.
Step 3: Select Date/Time Setup; press ENTER.
Step 4: Enter the current date by using the left and right arrows to select the field, and the up and down arrows to change the value. Press ENTER, and follow the same procedure to change the time.
Step 5: Verify the date and time are correct; press EXIT.
Step 6: Repower the MicroGas unit.
Step 7: Verify that Maximum Time Remaining is counting down.

If you have any problems or questions, contact OTC Technical Services at 1-800-533-6127.

What is needed to update a Monitor 2000?

The only option is to trade-in your 2000 for an Enhanced Monitor. The Trade-In Kit, No. 3342, covers 1979-1999 domestic vehicles, and is OBD II, and Ford DCL compatible.

What is needed to update a Monitor 4000E?

A Monitor 4000E can be updated using the current Pathfinder '97 Basic Update kit, No. 3305-100. This kit covers 1989-1997 domestic vehicles. When updating from 1992 or older software, a new Ford cable is required, No. 3305-58. In order to access OBD II or Ford DCL, an additional adapter will be required, No. 3305-75. An alternative to the adapter and the Pathfinder '98 Update, is to trade-in your 4000E for an Enhanced Monitor with OTC's Trade-In Kit, No. 3345. This kit covers 1979-1998 domestic vehicles, and is OBD II, and Ford DCL compatible.

What is OBD II?

On-Board Diagnostics Generation Two systems, otherwise known as OBD II, can be found on selected 1995-96 and newer vehicles. OBD II is an expanded version of OBD I which has been required on California vehicles since 1988. OBD II is an emissions based regulation that monitors emissions related components and systems for failures, and can trigger diagnostics when no driveability concerns are noticed.

OBD II also uses a different type of digital data stream than non-OBD II vehicles; it's called CLASS 2 communications. Traditional communications called UART, toggle a 5 volt line to 0 volts at 8,192 bits per second. CLASS 2 communications toggle from 0-7 volts at a faster 10.4 kb per second rate. In CLASS 2 communications, data is pulse-width modulated , having either a short or long length digital pulse, compared to only a short pulse for UART. Therefore, CLASS 2 data requires a scan tool capable of reading the new communications.

OTC's Enhanced Monitors are fully OBD II compatible. However, the Monitor 4000E requires the use of an OBD II Plus Adapter, No. 3305-75. Monitor 4000E owners can use Pathfinder III Software, No. 3305-80, or Pathfinder '97 Software, No. 3305-103 or No. 3305-100. You can upgrade your scan tool (no matter what brand!) by trading it in for an Enhanced Monitor Trade-In Kit, No. 3267.

Some 1994 and 1995 vehicles came with a standard OBD II diagnostic connector, but had traditional UART communications. For this, OTC has "Smart System Inserts" that plug into the OBD II cable to re-configure the cable for traditional communications. The monitor will indicate which insert is to be used once the VIN information has been entered. Generic OBD II insert, No. 3306-01 should be used on true OBD II vehicles.

What is a breakout box, and what is it used for?

A breakout box or B.O.B., tees into a vehicle's on-board computer system, and allows voltage checks on circuits while the system is in operation. A technician can check sensor voltage values, system power, and ground feeds without having to backprobe into connectors. This is especially helpful on vehicles that do not offer serial data through a scan tool. Any DVOM or lab scope will work with the breakout box. OTC offers a Universal Breakout Box, No. 3226. The No. 3226 does not include vehicle adapters which are necessary to connect to a vehicle. Contact your nearest OTC distributor for more information on what adapters area available. In addition to a breakout box, you will need a computer troubleshooting service manual, detailing which pins correspond to which circuits on the particular vehicle. OTC's Enhanced Monitor works with the B.O.B. to access trouble codes. And with the Pathfinder feature, it will provide you with useful B.O.B. information.

What is a lab scope, and what is it used for?

Vehicle computers process voltage signals from a variety of sensors. These voltage signals correlate to a given value. Some of these signals are processed by not just the voltage value, but by the voltage transition or frequency. Outputs from the computer also are not limited to a static voltage, but can be digitally pulse-width modulated. This means a traditional DVOM which averages these signals and does not show the quality of the signal, may not be enough for an accurate diagnosis. A lab scope gives a visual display of voltage levels correlating to time, similar to a graph, with voltage values on the vertical axis and time on the horizontal axis. The increments in which these values are displayed can be changed for the best resolution on the particular signal(s) being displayed. This allows the technician to visually detect a faulty signal. With a lab scope you can also measure frequency and duty cycle. The OTC Vision, No. 3800i has 4-channel capability, allowing you to view four signals at once. It also has the capability to display secondary ignition patterns. This is an excellent tool to compliment an Enhanced Monitor, and a breakout box.

Demystifying Oxides of Nitrogen

by Steve Zack - OTC Technical Trainer

Oxides of Nitrogen (NOx) are one of the four pollutants emitted by internal combustion engines. The others are carbon Monoxide (CO), hydrocarbons (HC), and sulfur dioxides (SO2). Like the other three gasses, excessive amounts of NOx are the byproduct of engines operating under something other than ideal conditions. In theory, a perfect running engine would create only these non-toxic by-products - carbon dioxide (CO2), water vapor (H2O), and heat. But even under the best of circumstances, even the newest of engines don't operate under ideal conditions. This deteriorates progressively as engine components wear, and we still haven't developed an engine control computer that can instantly and fully adjust to changes in temperature and atmospheric pressure.

What is NOx?

NOx is an odorless colorless gas that is a natural byproduct of combustion. By understanding the conditions under which it is formed, you're in a much better position to use sophisticated tools, like your engine analyzer, to pinpoint the mechanical or electrical cause of the excessive NOx readings.

Nitrogen exists everywhere in its natural state. Approximately 77 to 78 percent of the air we breathe contains 2 atoms of nitrogen (N2). This is a stable gas that is inert, meaning that it does not easily change its composition or form with other gasses. That is, until it reaches temperatures of approximately 2300 degrees Fahrenheit, which is well within the range of a typical combustion chamber. At approximately 2300 degrees Nitrogen atoms separate, as a result they now have a natural tendency to oxidize or bond with atoms of oxygen. Another 21% of the air we (and our engines) breath is made up of 2 atoms of oxygen (O2). NOx is one atom of nitrogen and unknown (or "x") quantities of oxygen atoms.

The Making of NOx

As the intake valve opens, the low pressure area formed in the cylinder is quickly replaced by air at an atmospheric pressure at 14.7 psi. The air combines with hydrocarbons (HC) in gasoline to form the basis for the combustion used to drive the piston and generate power. During compression, as the piston begins to rise, the molecules of air and gasoline will rub together creating friction, which becomes heat. As the molecules absorb the heat, they expand. As the piston continues to rise, the pressure within the cylinder continues to increase, causing even greater friction, which causes the temperature to rise, allowing the gases to expand even further.

As they absorb the heat, the hydrocarbon molecules will separate into hydrogen and carbon; and oxygen molecules (O2) will separate into two individual oxygen atoms. With spark ignition, one oxygen atom will oxidize (combine) with two hydrogen atoms to create water, and two oxygen atoms will form with one carbon atom to create carbon dioxide. As oxidation increases, the newly created water and carbon dioxide create additional pressure, which the engine converts into usable power to turn the crankshaft and power the vehicle. As long as the combustion chamber temperature remains below 2300 degrees Fahrenheit, the nitrogen molecule will remain inert, which means it won't separate into individual nitrogen atoms and combine with other gases. But at 2300 degrees, bad things happen to basically good gasses. The nitrogen molecules separate, and bond with oxygen to form NOx.

Obviously the solution would be to keep cylinder temperatures below 2300 degrees Fahrenheit, and certainly considerable progress has been made in that regard. But the combustion area in the cylinder contains many "pockets" where temperatures will be significantly higher than in the rest of the cylinder. Any area not directly surrounded by a cooling jacket is an obvious candidate.

To help prevent temperatures conducive to the formation of NOx, engine manufacturers have installed an EGR (Exhaust Gas Recirculation) valve and passage to recycle exhaust gas to cool the combustion chamber down. Over the years they have also lowered compression ratios to reduce friction of the gases, thus lowering combustion temperature. A richer fuel mixture also creates additional hydrocarbons to absorb the heat, and retarded timing advance is another part of the strategy to reduce combustion chamber temperatures. The downstream catalytic converter has a rhodium cell used to convert NOx to nitrogen and carbon dioxide.

Using a 5-Gas Analyzer to Diagnose NOx Causes

NOx can be formed by many component failures and system malfunctions - anything that allows the combustion chamber temperature to exceed 2300 degrees Fahrenheit. For example, if the cooling system is utilizing pure water, it will absorb combustion heat and obtain its boiling point rapidly, leaving an air pocket around the combustion chamber. The air pocket will become a hot spot allowing for the combustion chamber temperature to rise. Equally bad is 100% antifreeze, which forms a blanket around the combustion chamber, keeping heat in and allowing the combustion chamber temperature to rise. Rust surrounding the cooling jacket surface will create the same blanket around the combustion chamber. Poor flow through the radiator, as a result of a blockage or poor circulation, or a partially closed thermostat or limited flow from the water pump, will prevent the high temperatures from escaping through the cooling system. This temperature increase will cause preignition, allowing the oxygen to prematurely oxidize the hydrogen, reducing the available air and fuel during spark ignition. As a result, oxygen will be limited to complete the oxidation of the hydrogen and formation of carbon and oxygen into carbon dioxide will be limited. In this case the gas meter will read high HC, low CO, low 02, low C02, and high NOx.

As the piston rises during the compression stroke, the opposite force of compression in the upward direction and the downward force created as a result of preignition will cause the piston to rock, slapping the piston skirt against the cylinder wall, causing a knock. As a result of an engine knock, we should see the scanner knock reading indicate yes, with a command to retard ignition timing. The secondary ignition scope should have a higher than normal firing line. With excessive preignition, the early flame front comes in contact with the spark ignition flame front. This will result in high HC, low CO, high 02, low C02, and high NOx. The horsepower of the engine will suffer as well.

A lean condition as a result of a false signal from the oxygen sensor, an out-of-calibration MAP sensor, plugged injector, low fuel pressure, low fuel pump volume, or a vacuum leak will cause NOx as well. Under these conditions the oxygen will oxidize the hydrogen and the carbon, creating extreme combustion chamber temperature. This acts much like a cutting torch used to oxidize the carbon atom of the metal. As the temperature climbs the nitrogen atoms will separate and form with the oxygen atoms to create NOx. As the oxygen is used to form NOx, the oxygen will be used up, causing a lot of hydrocarbons to be unused. The gas analyzer will read high HC, low C0, high 02, low C02, and high NOx. The secondary ignition scope should have a higher than normal firing line, and longer than normal spark duration. The scanner would read zero to low oxygen sensor voltage and a lean condition. As a result of running lean, the additional HC from a richer mixture is not there to absorb the heat. Therefore, the CO molecule needed in the catalytic converter to cause the catalyst to reduce NOx to nitrogen and carbon dioxide will not be created.

If the EGR system were not functioning properly, as a result of a plugged or partially plugged passage, inoperative EGR valve, inoperative vacuum control system, or an electronic malfunction, the controlled exhaust flow would not occur. This would allow the combustion temperature to rise. The gas analyzer would see high HC, low CO, low O2, low CO2, and high NOx as result of a faulty EGR.

Carbon build-up on top of the piston or on the cylinder walls may also cause preignition. This would give similar results to the cooling system issue. The carbon build-up could be as a result of running extremely rich for any length of time. Therefore, when repairing high CO emissions failures, always assume that carbon has formed. This type of carbon can even be caused by oil consumption, which will also cool the combustion chamber temperature. Carbon on the throat of the valve will absorb fuel, causing a lean condition and giving a similar result as to the previous lean condition. This type of diagnosis may require a borescope to visually inspect pistons, cylinder bores or valves. To repair this, a chemical top end cleaner may help. If the vehicle is not running rich, the gas analyzer will read high HC, low CO, high O2, low CO2, and high NOx. The reason for the high O2 is that the carbon will assimilate a lean ignition misfire. The scanner would read low oxygen sensor voltage. The secondary ignition scope should have a higher than normal firing line, and a possible appearance of second firing line in the spark line.

A worn or slipping timing belt can certainly increase internal temperatures. If the timing belt or timing chain has excessive slack, the cam timing will be retarded. The camshaft will be behind the crankshaft resulting in the camshaft lobes not opening the valves in the proper relationship to the piston. The intake valves during the intake stroke will open late, causing the air to continue entering the cylinder later than required. As a result, the compression pressure will increase at the top of the compression stroke and temperature will reach its maximum later on into the stroke causing a longer oxidation period which results in extreme combustion temperature. As a result of late intake valve opening, the vacuum will be low, causing the MAP sensor to see a load adding more fuel, causing high CO. The gas analyzer will read high HC, high CO, low O2, low CO2, and high NOx.

If the base timing is advanced too far, the spark plug will ignite the air fuel mixture early, causing the combustion temperature to rise as the compression stroke continues, causing NOx to form. With a very early flame front in the compression stroke, as a result of advanced ignition timing, the temperature created as a result of early oxidation will cause the temperature created during compression to rise extensively.

The exhaust valve seating surface is not just to seal the cylinder airtight, but to provide a means of removing heat from the valve and disbursing it to the cooling system. An exhaust valve that is improperly seated will not transfer heat. As a result, the valve and its seat will rise in temperature, causing preignition. This will result in high HC, low CO, high O2, low CO2, and high NOx.

So as you can see, excessive NOx is caused by high internal temperatures. Unfortunately, there are any number of factors that can increase combustion chamber temperatures past the magic 2300 degrees. Fortunately, with your trusty five gas analyzer and a little reasoning ability, you're in great shape to isolate the problem, replace the faulty components or make adjustments as needed, and send the motorist on their way with a better performing and lower polluting vehicle.

copyright SPX 2007