Flash reprogramming PCMs is NOT for the feint of heart. It takes a considerable investment in equipment, paying OEM subscription fees to get flash updates on a CD or online, plowing though pages and pages of charts and tables and TSBs to figure out whether or not the calibration software in a vehicle's PCM needs to be updated, and then plunging ahead with the update itself
Yet PCM flash reprogramming is becoming more and more necessary as vehicle modules get smarter and more complex. GeneralMotors estimates that they have released flash updates for as many as 70% of 1995 and newer GM vehicles.PCM Programming is Nothing New
Would you believe flash reprogrammable PCMs have been in vehicles for more than a decade? The first such application was the 1990 Geo Storm. Why a humdrum car like the Storm would be the first to receive a flash reprogrammable computer system is unknown. You would think GM would have chosen a more high profile vehicle like a Cadillac or Corvette to usher in the new technology. But they didn't. The choice probably had more to do with production scheduling and new model introductions than profile or image. GM knew OBD II was coming and that it would require a new generation of PCMs that were faster, more capable and able to be programmed electronically.
Up to this point, Program Read Only Memory (PROM) chips held all of the PCMs vital calibration information and operating instructions. GM pioneered the replaceable PROM chip as a way of programming a limited number of basic PCMs to fit a wide range of GM makes and models. A replaceable PROM chip also meant the PCM could be "retuned" if necessary to correct certain kinds of emissions or driveability problems. It also meant that if a bug was later discovered in the original factory programming, it could be corrected in the field by simply replacing the original PROM with an updated corrected PROM (a tactic GM has successfully used over the years to fix many factory flaws). Performance enthusiasts also liked replaceable PROMs because the chip could be replaced with one that provided more spark advance, fuel enrichment, a higher rev limit, etc., to squeeze more power out of the engine.
But replaceable PROMS had a serious drawback: there were too many of them! Every model year and every running change meant another PROM had to be created. Every field fix or recall for an emissions or driveability problem created more part numbers to keep track of. We are talking thousands of different PROMS. The General Motors PROM Identification manual that OTC used to provide with their Monitor scan tool and Pathfinder software contained more than 362 pages of GM PROM numbers!
Enter the flash reprogrammable EEPROM (Electronically Erasable Program Read Only Memory) chip. PCMs built with EEPROM chips can be reprogrammed in a matter of minutes without having to remove the PCM or replace a single chip. It is all done digitally with the proper access codes and input data.
Following the Geo Storm, GM began phasing in PCMs with flash reprogrammable chips in a variety of cars and trucks. By 1995, most GM models had the flash reprogrammable PCMs. Ford and Chrysler were also doing the same thing as OBD II arrived on all cars and light trucks in model year 1996. Today, almost all PCMs have reprogramming capabilities as do a growing number of other onboard control modules (ABS, air bags, climate control, body controller, etc.), so changes and upgrades can be made if needed.
for a list of vehicles with reprogrammable PCMs, Click Here.
A reflash may also be required if the factory settings for the OBD II self-diagnostics turn out to be overly sensitive - especially after a few years of operation. The same goes for driveability. What works fine in a brand new car many not work so great after 50,000 or 100,000 miles of real-world driving. Changing the fuel enrichment curve, spark timing or some emissions control function slightly may be necessary to eliminate a hesitation, spark knock or other condition that develops over time.
For example, on certain GM vehicles the Check Engine light comes on and sets a code P1406 that indicates a fault in the position of the exhaust gas recirculation (EGR) valve. Cleaning or replacing the EGR valve and clearing the code does not fix the vehicle because the code usually returns. The real problem is the OBD II programming in the PCM. When the PCM commands the EGR valve to open to check its operation, it isn't allowing enough time for the valve to respond. A brand new valve takes only about 50 milliseconds to open but an older valve may take up to 350 milliseconds or longer - which is not long enough to cause a real NOx emissions failure but is long enough to trip a fault code. The fix in this instance is to reflash the PCM with new instructions that allow more time for the EGR valve to respond.
Another example are rich codes that may appear on some late-model GM vehicles. The problem here is that the original OBD II self-diagnostic programming does not allow enough leeway for changes in intake vacuum that occur as the engine ages. After 60,000 miles, intake vacuum isn't as high as in a new engine, which can create a rich fuel condition. The cure is to flash reprogram the PCM to compensate for the drop in vacuum.
When vehicle manufacturers calibrate the onboard diagnostics to meet federal emissions standards, they have to draw the line somewhere as to what operating conditions might cause emissions to exceed federal limits 1.5 times. That is the threshold where a fault code must be set and the Check Engine light must come on. It doesn't mean emissions really are over the limit, but it is possible based on laboratory dyno testing and field experience. Depending on the application, the vehicle manufacturer may even set the limit a little lower just to be safe because the last thing any OEM wants is an expensive emissions recall.
Unfortunately, vehicle manufacturers don't always tell us their diagnostic strategies or even their operating strategies for their computerized engine control systems. Some service manuals include a fair amount of system background information but others provide almost nothing beyond a basic diagnostic flow chart. Maybe the engineers who design this stuff think technicians only need flow charts and assembly instructions to fix vehicles today. But it often takes a much deeper understanding of the system operating logic to figure out what's setting a particular code - especially when the cause isn't obvious.
The best advice when confronted with a troublesome code that keeps coming back or seems to set for no apparent reason is to check for any technical service bulletins that may have been published. Chances are it might be a programming issue that requires a reflash to fix.
Something else to keep in mind with respect to many late-model flash reprogrammable PCMs: if you replace the PCM for any reason, the replacement unit may have to be reflashed before it will start the engine! Some modules are plug-and-play, and are preprogrammed by the dealer so they can be installed ready-to-go. But many need vehicle specific calibration information to run properly. This may require downloading old calibration information from the original PCM (if possible) and reloading it into the replacement PCM, or getting updated calibration information from the vehicle manufacturer to install in the new module.
Some remanufacturers who supply reconditioned PCMs now flash program PCMs for specific vehicle applications. But to do this, they need vehicle information such as the vehicle identification number (VIN), the type of transmission (manual or automatic), the emissions type (federal certification or California), and other options thqat may affect the calibration of the PCM. Your other option is to flash reprogram the PCM yourself.
Not Just Dealers Anymore
Until recently, car dealers were the only ones who had access to the tools and software needed to reflash PCMs. Thanks to the passing of Senate Bill 1146 in September 2000, vehicle manufacturers must now make this technology available to independent repair shops at reasonable cost.
Starting in 2004, flash reprogramming procedures must also conform to SAE J2534 standards that allow the use of aftermarket scan tools or similar pass-through devices.
Reflashing PCMs requires three things: a scan tool or J2534 pass-through device that is flash capable, a Windows 98 or higher PC with a modem and Internet access for downloading the flash software from the vehicle manufacturer's website (Click Here for a list of OEM Service Websites & Access Fees), and a subscription to the manufacturer's database so you can access the software or get the software updates on CDs. Other items that are needed include a cable to connect the PC to the scan tool or J2534 pass-through device, and a cable to connect the scan tool or J2534 pass-through device to the OBD II connector on the vehicle.
For GM applications, you need a Tech 2 scan tool or Vetronix Mastertech.
For Ford applications, you need a Ford New Generation Star (NGS) scan tool, or their new IDS scan tool.
For Chrysler applications, you need a Diagnostic and Reprogramming Tool (DART) or a Chrysler DRB III scan tool. These tools are available from OTC Div of SPX Corp. To view or download a copy of the DART users manual, Click Here (The manual is a PDF file).
For import applications, you need whatever factory scan tool the dealer uses, an aftermarket scan tool with reflash capabilities for that vehicle, or a J2534 pass-through device that will work on the vehicle.
Yearly and monthly access fees to OEM databases tend to be very pricey for the average shop, but one-day or short-term access fees are typically available for $20 to $25. These costs are usually passed along to he vehicle owner when a shop has to access online information.
On GM and Chrylser applications, flash updates are supplied on CDs once you pay a subscrption fee. With Ford, the softare is downloaded from their website via an internet connection. The software is then loaded from the CD to your PC. From here, the software may be copied to a flash card which is then plugged into a scan tool for transfer to the vehicle, or it is copied through the J2534 pass-thru box or scan tool to the vehicle. With Ford, you have to keep a live internet connection for the duration of the procedure because Ford loads the software into the vehicle directly from its own server).
The flash procedure can takes from a few minutes up to an hour depending on the file size of the softare you are installing. The newer and more complex the vehicle, the longer it typically takes to flash the PCM.
Did You Know...
Some of the other players you can expect to see in the flash reprogramming arena include Hickok Tools , CARDONE Industries , Drew Technologies and OTC Div of SPX Corp.
GM Flash Updates
On GM vehicles, a list of flash updates that are available can be found on GM's Vehicle PCM Calibration Information website at http://calid.gm.com or http://tis2web.service.gm.com/tis2web.
The actual reprogramming procedure for a typical GM vehicle goes as follows:
Note: The GM setup will NOT allow the same calibration to be reinstalled over itself. Only an updated calibration can be loaded into the vehicle computer. There is no going back to an earlier version.
To get the actual calibration download, click on the "Reprogramming & Initialization" link at the left. You then have to buy a one-day subscription before you can download the software to your PC that is necessary to do the reflash. You will also need a J-2534 pass thru tool to do the reflash.
With Ford, the calibration software that will go into the car is not stored on the PC. The software that you downloaded only facilitates the transfer of the new calibration from Ford into the car. In other words, it is a "live" procedure that requires a continuous unbroken internet connection until it has finished.
Chrysler Flash Procedure
Chrysler's flash procedure is sort of a cross between GM and Ford's procedures. First you go to the www.techauthority.com website and download their "benchtop Programmer" software to your PC. Then you download a huge pdf file ("J2534 Flash Availability") that lists all Chrysler PCMs and their software updates. Chrysler uses vehicle body codes to identify the PCM in addition to the VIN, and you need to use a scan tool to get the module ID from the vehicle. If the vehicle needs a update, you go back to the Chrysler website, pay their access fee, and download the new software to your PC. Then you transfer the software from the PC to a scan tool or J-2534 pass-through tool to install it in the vehicle.
Also note, many Chrysler PCMs require a re-initialization procedure after a flash. For more information about this, click here (requries Adobe Acrobat to open pdf file).
Here is a sample of the flash reprogram procedure a Chrysler dealer would use. This one happens to be for a recall Chrysler issued for 1999 California Dodge Ram Pickups and Vans with 5.9L engine ("Z" engine code in the 8th VIN position), automatic transmission and California emissions control system (code NAE). The OBD II catalyst monitor on these vehicles may not detect a catalyst failure so the PCM programming had to be revised to comply with California regulations.
The dealer accesses the latest software through the modem connection in the Mopar Diagnostic System, and feeds it through the DRB III scan tool into the vehicle's PCM via the OBD II connector. The process begins by turning the ignition key on (engine off) and allowing the scan tool to "auto connect" with the PCM. Once the lines of communication are open, the VIN is displayed on the scan tool. The technician can now press the "OK" button to proceed with the reflash procedure.
The first thing he does is select "Read Part Numbers From Vehicle" and click "Show Updates" on the MDS2. If somebody has already reflashed the PCM, the screen will say "Part number is up to date and does not require any new updates." The software number should be compared to the latest version to verify the numbers match just the same. If the PCM has not yet been updated, the technician clicks OK, selects the new software part number and clicks "Update Controller Software." From that point on, the process is automatic - but there is a hitch. During the flash reprogramming procedure, the PCM loses communication with other modules on the vehicle that may set a number of "false" trouble codes for the transmission module, ABS module, body control module, etc. This does not indicate a problem and the codes can be erased after the flash reprogramming procedure has been completed. The technician is also supposed to attach a label to the PCM with the reflash part number and date indicating the PCM has been reflashed.
WARNING! PCM Flashing Is Not Without Risk
So what happens if something goes wrong during a reflash procedure? Anyone who has ever experienced a crash while installing new software on a PC knows it can cause real problems. In some cases, the PCM may be so scrambled that it will not accept a reflash, which means you get to buy a new PCM!
Chrysler issued a TSB (18-32-98) that deals with how to recover from a flash reprogramming failure.
The bulletin says, "Occasionally a flash update procedure may not complete properly and/or the diagnostic equipment may lock up during the procedure." Common causes of flash errors include poor cable connections between the PC, scan tool and vehicle, loss of power to the diagnostic equipment while the flash procedure is underway, turning off the vehicle ignition switch before the flash procedure is complete, unfamiliarity with the procedure (pushing the wrong buttons), or low vehicle battery voltage.
If the process crashes, recheck all the cable connections to assure good communications and reinitialize the flash procedure. In other words, if at first you don't succeed, try, try again. On the Chrysler applications, you may also have to identify which type of controller is on the vehicle (SBEC2, SBEC3, JTEC 96-98, JTEC+ 99, etc.) to get the system to accept the new programming. If you get an error message again, you probably selected the wrong controller type (try again!).
Doing your own flash reprogramming is not without risk. But for some shops it may be a more practical and profitable alternative to sending vehicles back to the dealer when a PCM needs to be updated or replaced.