The first computer cars arrived in 1981 and with embedded computers came the capability to control engines to a degree impossible before. This control was necessary to meet new Corporate Average Fuel Economy (CAFE) regulations, first enacted by the U.S. Congress in 1975 in the wake of the 1973 Fuel Crisis.
Earlier, except for a few oddballs who bought things like Volkswagons and the first Minis for "economy", the early 70s were the heyday of the Great American Land Barge (GALB) weighing over two tons and with 400-500 cubic inch engines to move them. When gas was under a dollar a gallon, range was a function of tank size not MPG
In 1973, as I recall the worst gas mileage year in the US, people commonly experienced averages below 10 mpg
CAFE arrived in 1975 with an initial goal of 27.5 mpg for passenger cars by 1985. In 2011 this rose to 30.2 mpg. Note: the "A" in CAFE is for "Average". In order to sell a high-profit 20 MPG guzzler, corporations must sell a number of cars that exceed requirements. The Chevrolet Volt is a good example of a car designed to raise the CAFE for GM. Since the 2012 Grand Cherokee is the best selling Jeep and also has a rating below the CAFE this puts Chrysler in an "interesting" position.
In order to meet these goals while also meeting emissions standards (Clean Air Act) required very precise control of the engines and this required computer controls. The first GM computers had a 2 MHZ 8 bit processor and 2K of ROM (CCC or Computer Command Control) that communicated at 160 baud.
These were phased out starting in 1986 by a new P4 computer with 256k of ROM and 8192 baud communications. The 1988 Reatta had three main computers (ECM (engine), BCM (body & HVAC), and EBCM (brakes)) plus numerous modules interconnected by a serial LAN called the ALDL (Assembly Line Data Link). Note: In 1988 home computers were just transitioning from 1200 to 2400 baud modems. Reprogramming P4 computers required removing and replacing the PROM though hobbyists quickly determined that the PROMs could be erased and reprogrammed.
Quickly whole subcultures grew up around "chipping" or reprogramming the computers so the cars ran more in line with what was desired. Equally quickly frauds and miracle devices showed up to double horsepower or fuel economy and sometimes both.
Personally limit my changes to permit an engine to run about 10% cooler than stock and prevent excusions. Factory engineers really do a very good job of programming for both economy and power (sales points) though their agendas are a little different from mine.
Meanwhile back at scanners. While scanners (e.g. GM Tech-1) have existed for as long as computer controls, early ones were expensive. Today early ones like (my preference) the OTC-2000 often show up inexpensively on eBay, you just need to be sure to get the right cables and cartridges). However every manufacturer had their own data stream and every make model and year had a different sequence. Professionals needed yearly updates for every car line they serviced.
NHTSA decided the multitude of different sequences was too confusing and made emissions testing difficult. For 1996, every car sold in the United States, both domestic and imported, had to conform to OBD-II, a government standard for basic communications with automobile and light truck computers. OBD-II mandated a standard set and format for error codes (P-xxxx) and a basic set of sensor readouts (PIDs).
A list of standard P-codes can be found here along with some special codes for different car lines.
In addition to the P-codes, OBD-II aso provides a number of sensor parameters for things like RPM, MPH, Coolant Temperature, & Injector Pulse Width. These are know as PIDs or Parameter Identification. SAE J1979 defines many standard PIDs but manufacturers also define many others specific to their vehicles. Many of the standard codes and calibration information can be found here.
Note: most vehicles support only some of the codes. For instance usually an engine has Mass Air Flow rate (MAF - PID 10) sensing or Intake Manifold Absolute Pressure (IMAP - PID 0B) but very rarely both. As part of setup a good program will strobe the data line for which PIDs are supported. Some will even know special codes for different car lines.
However, other than these standard readouts, manufacturers were free to add their own "proprietary" commands and connections for things like dumping and flashing the PCM. GM, Ford, and some imports make these extended commands available however Chrysler does not and these extended codes for things like tire pressures will need to be reverse engineered.
Personally, I prefer PC or Tablet based scanners since all that is needed is an OBD-II connection and software to send/receive. Interestingly, the most common OBD-2 chipset (ELM 327) commands seems to use a superset of the Hayes AT modem command set.
Might mention that the most standard chipset is also the most copied both as emulations (STN1100) and as clones (e.g. Chinese knockoffs often identify as v1.5 which is not an ELM version)
Currently there are two kinds of connection:
1) Cable based and USB terminated
2) BlueTooth (wireless).
The advantage to USB is that most OBD-II PC software can use. The disadvantage is that I have not found any that work with Android tablets and are tethered. Bluetooth OTOH works with both PC software such as TouchScan and Android software such as Torque
Since this was originally written, I have acquired a tablet with Android 4.0.4 (Ice Cream Sandwich). It and the current version of Torque is able to use the USB connector through an adapter.
Note on Torque: It is an effective and well regarded software package for Android tablets however if you do not have access to the Android Marketplace (my G-Tablet does not), it is difficult to find another download site.
Am currently using several devices: an Acer Netbook with Touchscan for the PC world and Viewsonic (10"), Kyros (7"), and Samsung Galaxy Tab 2 7.0 for Android. I have a MacBook and an iPad but find Apple products to be limited in capability and too expensive in comparison. May expand to an iPad if I acquire one. Connection is via a USB dongle from Scantool.net and what appears to be a knockoff (invalid version) Bluetooth dongle from BAFX. Some but not a lot of study was done before selection. Did know that being able to clear codes as well as reading them was an essential attribute.
See also my Thoughts on Tablets.
The current test platform is a WK2 Jeep Cherokee with Pentastar engine. I have also used with a 1997 Buick Roadmaster but do not have access to that at present. My other vehicles are all pre OBD-II. See Appendix 1 for available Jeep PIDs
My first experience was with the USB dongle and OBDwiz which was effective as a low-cost all-in-one solution. There is an active forum for discussion and questions.
Since then I have been using Torque and a 10" G-Tablet to provide a digital dash in the place of the dash I cannot read with sunglasses on in the Jeep. This is able to provide a sunlight-readable display of 17 parameters. I have no problems with digital displays and read very fast. Others may precer circular, bar, or even graphing displays. While all are possible I find the most information can be placed in a digital display format.
In order to create this display, I found it easiest to delete all of the default displays and create an entirely new dashboard. This is easiest while connected to the car since available parameters are identified in green making it simple to determine which are available for use. This is also reflected by OBDwiz/TouchScan in that when selecting displays, if the search function is used while the connection is active, only available parameters will display
All software mentioned is capable of data logging though parameter selection is not automatic. Just as specific parameters may be selected for the realtime display, the same (or different) parameters must also be selected for logging. Similarly setting for automatic recording at one second intervals can quickly exhaust memory, particularly on a tablet or telephone. Best to set to manually start and stop with a new file created each time. I also set to record in CSV (comma separated variables) format since is easy to import into a spreadsheet for analysis.
Once the vehicle is equipped, it is best to run a series of baselines: recorded identical passes that may be used to compare to similar runs after modifications. The first such will probably be a cold air intake (CAI) package
It is now about six months since the previous was penned. I am
still looking for a composite input device that works with Android and am up to
four devices in my car but are a little different now.
Addendum, October 2012
It is now about six months since the previous was penned. I am still looking for a composite input device that works with Android and am up to four devices in my car but are a little different now.
Three different display devices (MiFi not shown)
Caution: Plugs ahead
Guess I have mixed emotions about Samsung, while the help desk has not been much help, their products/prices have a set of features that are hard to resist. Despite their redacting HDMI capability from the Tab 2, I now have a Samsung Bluray player, Tablet, and Proclaim cell phone all of which play together well & communicate wirelessly. I also have a MiFi mobile hot spot. Both the cell phone and the hotspot use Verizon lines and were able to remain in contact in some remote parts of North Carolina where my "other" cell phone could not get a signal. All of the above except the MiFi device have SD card capability. I consider that essential.
All of this is going to be needed in the future. We have capabilities that have been a dream for some time but just becoming reality now. I just hope the current trend toward less features is stopped in its tracks and the trend toward one person/one device/one price continues. My belief is that this is critical to prosperity. Now that I know better, I will not buy another intelligent portable device that does not have a removable SD card.
Think my first articles about belt devices were over two decades ago just as people were getting used to the idea of a personal computer and Michelangelo made its rounds. Back then anti-virus was a hobby and I gave away detect/repair software. My phone is an ideal example of something that is complete in itself yet can support other I/O devices without a problem. The display is minimal but functional and it can support remote systems. I get into my car and a link is made automagically. Can take pictures and display on my TV when home. Has full automotive diagnostic capabilities (though I prefer to use the tablet, can only show 6 parameters on phone but tab shows 19). Can act as a hotspot for other devices or use local WIFI when available.
3.7" Cell Phone Display
Current 7" Tablet display (mostly city driving)
Today I rarely write software but may get back into it. An currently surrounded by technology and have been "connected" since the '80s. Have seen a lot of transitions and today have redundant everything. Do think we are right on the brink of a time when everyone is connected. Anywhere/anytime.
Is nothing new in the USofA. With any new technology, 2,000 nuts come out of the woodwork with ideas how to make it work. Some will be right. Do believe we are real close just hope too many proprietary and nonexpandable/nonrepairable systems are not allowed to block what is possible. See also Comments on Tablets.
Above Links last verified 3 April 2012.
The above are the devices and software I have used so far & seems to be sufficient for my purposes. There are others mentioned on forums which are listed below. I have not tried these.
From a post by shadetreemechanic - see note at bottom
TouchScan: TouchScan is designed for touchscreen use but also works with laptops/PCs. A fully functional 2-week evaluation version is available on the link below (in exchange for your email address): Trial Version or To buy
Digimoto 5 Demo: (Crippleware, works 7 Days, 15 minutes per session) Link Click on: "Where Do I download Digimoto 5?"
OBD 2007 for PC, OBD 2007 for Pocket PC:
(Free 7 day functional demo avail)
FREE (ish) & UNCHECKED:
Scanmaster Free v0.4.0.0 (old version, may not work on latest scantools): Link
ScanmasterELM_Demo 2.1, (new version, now Nagware): Link
Digimoto Lite 1.06: Link
wODB 07/10/04: Link
OBD Logger: Link
Mac OSX / Linux: Link
OBD Gauge for Palm OS, Pocket PC, OBD Graph for Windows: Link
OBD 2007 PidReader
Above links were adapted from a post by shadetreemechanic "OBD II Software List" on: May 16, 2010, 03:06:15 AM with comments redacted. I have not checked these.