Most helpful critical review
249 of 269 people found the following review helpful
Basic code reader. Not many features.
on March 24, 2009
This is a basic OBD code "reader", not a ScanTool. It can read an OBD code number IF an error has been stored by your vehicle and it allows you to view it and reset it. If the check engine light isn't on (due to a stored OBD code/value out of spec) then it wouldn't have much info to tell you. As an entry level code reader it can't read any of the useful features and data available via the OBD protocol such as engine temp, rpm, percent engine load, throttle position, oxygen sensor voltage, lean, rich trim data, MAF sensor, EGR valve position, and so forth. Most vehicles have over 80 sensors and variables that can be displayed and slightly higher end OBD ScanTools (some starting at $65) can read many of those variables which is very useful in fixing your car.
I have a background in automotive and industrial electronics and I hope providing some details on OBD code readers of this type is useful to someone.
The model 3100 retails for nearly $90 but isn't the best value considering the limited feature set. It's not able to check battery voltage, mpg, speed, vacuum, RPM, or other variables even though the data is there if they design the unit to use it. This is a "Code Reader" only and as such there is no real-time display of engine parameters other than if the O2 sensor (fuel control) is in open or closed loop mode. "Open loop" engine control mode means the engine runs on stored fuel delivery set points and estimates based on throttle position, temperature and other inputs until the O2 sensors warm up enough to start functioning. This typically takes 2 minutes or less for modern heated O2 sensors and then it goes into "closed loop" mode. That uses the data (feedback) from the O2 sensors to adjust fuel rich/lean mixture as needed which completes the fuel mix control loop with active feedback.
A code reader like this one is useful for translating a check engine light into a number and it provides a useful short text version of what the stored OBD code means such as "O2 sensor bank 2 is low". That can point you in the right direction of what the issue is. Meanwhile an OBD Scanner can read the code and sensor parameters as well. So if your O2 sensor voltage is slow to respond (for example) the scanner can read that, while the code reader can't. On scanners you can also see the value change if you unplug the sensor so you know you're replacing the right one while readers can't do that.
The main downfall of this type of tool is that if the vehicle control systems didn't record or encounter an issue then the reader won't have anything to report. It will just say "There are no codes stored".
Note that most of the functionality of a Code Reader is provided by the vehicle itself. The vehicle computer monitors various sensors, checks the data vs known acceptable ranges, triggers the check Engine light if needed, and stores a small snapshot of data at the time the code is set. If the problem clears up (due to 1 tank bad gas for example) the vehicle will eventually reset the check engine light itself after enough drive cycles (full warm up and cool down over a period of days). If the problem remains the light stays on. Note that some cars have the lamp burnt out and have a code set but you may not see that unless you change out the dash bulb or connect a reader to see.
Overall there are some better products available for less money such as an entry level OBD Scanner. Some at a similar price point can be left plugged in like a set of extra gauges that can display MPG, ignition timing, percent load and other parameters that you select such as the UltraGuage for about $65.
Some ScanTools can display and store engine parameters for review later or print out using your computer so you can talk it over with your mechanic. Other units will interface to other vehicle computers including the transmission, braking, body control module, ABS and many others.
If you already own this tool hopefully it served it's purpose and has been useful to you by pointing you in the right direction based on the trouble code. If you're in the market for an OBD reader I suggest considering a scantool instead. Those are a better value with much more features and some are actually cheaper than basic code readers anyway.