by Lih-Tah Wong
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Auto Gear - ScanGauge II Car Diagnostics

Added 01-21-2009

I have always wanted a device to read my cars' Diagnostic Trouble Codes (DTC) whenever the  infamous Check Engine Light (CEL) would appear on the dashboard.  I would usually take my car to the dealership just to find out what the problem, but I wasn't happy to pay $35 just to learn that my wife did not put on the fuel cap properly.  No wonder many people refer to those places as the stealership!

About two years ago I learned that the auto supply store chain called AutoZone offers to read the DTC for free.  That's a terrific service, but what happens if that wasn't convenient?

One solution is to buy my own handheld scanner.  At $75+ I thought it was too expensive for such infrequent use and a small convenience.  What I really wanted was a device that had other functions but also included the ability to read the DTC as needed.  

In fact, while my car can calculate the fuel economy, it does so for the tank.  I wanted to know instantaneous reading this value, along with other parameters of my car's performance such as fuel consumption rate.  Did it really cut of fuel flow when decelerating in gear and the gas pedal was not pressed? 

Enter the ScanGauge II, a device that plugs into the On-Board Diagnostics (OBD) II port that exists in every vehicle sold in the USA since 1996.

It has three primary functions as shown in the picture:

1. DTC scanner that reads and also clears codes.  Clearing the codes for minor problems like an improperly closed fuel cap will extinguish the CEL.

2. Trip computer with many stored parameters for:

bulletCurrent trip
bulletToday's trip
bulletYesterday's trip

Current tank

3. Real-time (1-second refresh) gauge that can simultaneously display 4 parameters.


Trip information that is stored are:

bulletMax Speed
bulletAverage Speed
bulletMax Coolant Temperature
bulletMax RPM
bulletDriving Time
bulletDriving Distance
bulletFuel Used
bulletTrip Fuel Economy
bulletTrip Fuel Cost
bulletDistance to Empty
bulletTime to Empty
bulletFuel to Empty

The gauge parameters are chosen from among:

bulletFuel Economy
bulletFuel Rate
bulletBattery Voltage
bulletCoolant Temperature
bulletIntake Air Temperature
bulletEngine Speed (RPM)
bulletVehicle speed (MPH)
bulletManifold Pressure
bulletEngine Load
bulletThrottle Position
bulletIgnition Timing
bulletOpen/Closed Loop

You can even custom program other engine parameters if you have your car's technical service manual.  This add-a-gauge feature is called X-Gauge.

I find this device is worth its $160 price.  Since getting it, I learned a few things about my car:

  1.  I know how to get an extra 3-4 mpg with less aggressive driving so that my city fuel economy gets 25-26mpg.  I expect to get 1-2 mpg better on the highway.
  2. My car's engine management computer does indeed shut off the fuel injectors during deceleration as long as the engine runs above 1,050 rpm.
  3. When I shift down to a lower gear, the fuel injectors turn back on but I can force it to shut off again by briefly pressing on the gas pedal and releasing it.
  4. When idling at ~750 rpm my fuel consumption rate is 0.40 gal/hr.


Interested in knowing more about your own vehicle?  Click here to get the ScanGauge II.  



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