Palmer Performance Engineering code scanner / diagnostic tool

Software of this type often seems to get superceded by newer programs; updates and upgrades are not certain. Don't expect regular updates.

All cars sold today - and for the past decade, in the US - keep track of certain problems, and allow people to and see what has gone wrong. The result has been an industry selling code readers, some self-contained and some used with a computer, some of which let you record information from selected sensors. This can be useful for people with sporadic problems, and can replace the dealers' "copilots;" it also helps performance tuners.


Readings from various sensors are visible as one drives or makes changes, which can be invaluable for turbocharger tuning, taking the place of the traditional air-fuel, air intake, and vacuum/boost gauges; it has many uses for the skilled diagnostician. The Palmer Performance Engineering (PPE) PMCScan tool is the most flexible, powerful one we've used, but also one of the most frustrating once we left the basics and tried to delve into deeper workings of the program.

error codes

The Palmer PMCScan, like most systems of its kind, connects to the auto computer system, reads fault codes, and records or displays sensor readings; it also lets you create your own "dashboards" for display on your computer screen, taking it a step beyond the AutoTap system we reviewed before. These dashboards can include tables, virtual gauges (round, bar, and digital), and even cross-tabulation style tables combining the results of two different readings. Since you can make only a small number of readings per second, the more sensors you capture information from, the less often you can hit any particular sensor. This is a limitation of the car systems, not the Palmer software or hardware.

PCMScan window

A feature that takes Palmer Engineering's device further than AutoTap and many other systems is the second use as a tool to measure acceleration. For those of us who live nowhere near a drag-strip, this is quite handy for tuning and testing modifications; it provides a standard drag-strip "Christmas-tree" light display, providing plenty of warning for staging, and thus measures reaction time as well as actual 0-60 and 1/8-mile times (presumably measured from the moment a change in the speed sensor is detected). Unlike, say, the GTech accelerometer, you don't have to fiddle with a gadget precariously stuck to the windshield, and don't have to glue your eye to the speedometer, making it safer; of course if you slam on your brakes, you might need a new computer unless you have a passenger holding it.

drag strip feature of Palmer Performance Engineering PCMScan

A similar feature provides a rough estimate of your engine power and torque curves, provided you can provide accurate measurements of your tire diameter, vehicle weight, and final drive ratio; this time, you only have to accelerate up to redline in a single gear (presumably first), and the system does the rest, basing its estimates on your acceleration. It's not quite a full dyno but holding all else constant, it can provide a good tool for measuring increases in horsepower and torque, and getting a rough baseline.

The Palmer software works far faster than the AutoTap system, which takes several minutes to start up and figure out what the car's computer is capable of. Even on our slow, old, low-RAM Vaios, which topped out at 650 MHz, the Palmer software was quick to launch and took less than a minute to run through the "exhaustive" feature check. Running in a virtualized Windows environment (Parallels Workstation on a MacBook), it was even faster and quite stable.

The Palmer physical device is a small blocky thing, much smaller than the AutoTap, that plugs into the standard computer interface present on every car, usually right under the dashboard. On some cars you can easily drive with the adapter plugged in; on other cars, the device or its cable gets in the way of the clutch. For most people, this probably isn't an issue; however, the AutoTap, because it was considerably longer than the plug portion of the PCMScan, was much more awkward than the Palmer device. The Palmer PCMScan software can also work with third-party hardware - including AutoTap, which we found worked quite well PCMScan. It works on any OBDII compatible vehicle, including CAN models, which covers quite a range of models and years.

Both AutoTap and PCMScan are powered by the computer; the AutoTap is USB, while the PCMScan has a serial cable but comes with a serial-to-USB adapter. Installing PCMScan takes an extra step or two over the AutoTap because of this, if you use USB (which we had to on our Mac), but it's only a few moments to install the extra device drivers, the first time. The cable from the PCMScan OBDII plug to the serial port is long enough to be routed in a convenient route, and then it doesn't matter much how big the USB adapter is; and that gives more cord space before the computer is encountered.

PCMScan has a number of standard windows, including an oxygen-sensor test that was disabled for our test vehicle (a 2000 Chrysler 300M), a standard fault-code reader that provided a brief description of each code (presumably the SAE-standard definitions, about one line per code) and allowed for quick resets and additional information - which you don't get from all code readers - describing how many starts had been made since the code showed up, how many miles had been driven with the code, and other details. Like most devices of its type - the under-$10,000 variety - PCMScan usually sees only generic, or cross-manufacturer, codes. Thus, it can read the industry standard P0700 "there's something wrong with my transmission electronics" code, but not the more specific code that would tell you to replace the output sensor.

Another tab shows the status of the emissions monitors in a clear, easy to read display, another lets you decide what sensors will be logged, another lets you give instructions directly to the OBDII module. You can look at logged data frame by frame, or see it played back - at slow, real-time, or fast speeds. You can even write scripts for the program, use plug-ins (there is just one at the moment, for communicating with some Split Second devices), and set up alerts so that when a sensor reaches a certain reading, an alarm is sounded.

The dashboard windows, which display data in real-time using tables, graphs, gauges, and cross-tabs, are easy to read and quite snazzy, but setting them up is a serious chore; the best way is to use the examples and change them as needed. We never did figure out how to customize dashboards from scratch, and instructions are cursory or missing entirely for many features. Even changing the existing dashboards can be slow, with long delays when creating new items as fields are populated with usable parameters. The dashboards, when set up, reflect conditions with a time lag, so hitting the gas causes the engine load dial to flit upwards moments later; this seems to be an unavoidable condition of OBDII systems. The program does allow users to set up certain sensors as priorities, so that they are checked more often than others, which can result in much more responsiveness for key gauges. (Another solution is simply to shut off monitoring of unnecessary sensors). The system can read up to 40 items per second.

The range of sensors PCMScan can read depends on the model and year of the car; when first connected, it tries to find the VIN of the car, and gives the owner a shot at typing it in if it can't find one. Based on the VIN, it knows what to look for and can find some (but not all) "non-generic" information; it then takes about 1-2 minutes searching and finding data sources, based on our experience using an old 550-MHz Sony Vaio running Windows ME (you can save the car's profile and save time on the next hookup). Two different searches are available - long and exhaustive, or short and quick - the latter handy for just looking of codes, the former for more esoteric troubleshooting. We were rather disappointed that our 2000 test car didn't have some features of OBD, like monitoring of air conditioner status; but as cars get newer, they tend to track more items.

There is no Mac version, but the system worked perfectly on our Parallels Workstation-equipped MacBook. We see no reason why it wouldn't work under VMWare Fusion, as well. It may even work under WINE, though we didn't test that.

The full PCMScan software sells for $100; the hardware costs $130 for USB and $110 for RS232 (but, again, PCMScan works with other hardware, such as AutoTap). Together, the cost is $200 for RS-232 and $210 for USB.

The Palmer Performance Engineering PCMScan system is an excellent choice; it is priced closely to less capable systems, but has more features, including the gotta-have-it acceleration recorder and horsepower/torque estimator. The software remains under active development, and we think many prospective buyers of competing systems would do well to consider PCMScan at the top of their lists.

Palmer Performance Engineering home page

Those looking for a simpler device in the under-$100 range, which doesn't require a computer in the car, may be interested in CarMD.

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