Communication is important in every aspect of our lives, and particularly in our profession. Being able to communicate with customers, delivery people, parts providers and coworkers is the very basic mechanism that allows us to do our job with the kind of success that keeps us in business. Training for communication takes on many forms but, as yet, there is no substitute for experience. Communication skills are a learned and absorbed talent.
But what do you do when the communication is with a machine; one that just will not talk to you no matter what tricks you try? Where do you start when your significant other does that? You start with the basics, get to the root of the problem and work through it, or at least that is what is supposed to work.
This article is about communication faults and problems that have occurred on Volkswagens over the last 10-plus years. Many of the same problems still exist on the newest models, but as these vehicles age, get repaired or damaged, problems come up (see Photo 1) that can challenge even the very best technicians.
Photo 1: Hidden in all of this are the communication wires for various control modules.
The disclaimer for this article is that just about every time I think I have a full understanding of how VW puts its cars together and controls things, something changes. With OBD II diagnostics and CAN bus-connected components, diagnosis and repair should be getting easier, but the pattern failures continue to point to new and different failures.
Having the proper and updated test equipment is the only way to properly diagnose these cars, but there are some steps that can be taken before you make a huge investment in equipment for cars you don’t see on a regular basis.
I am going to focus on some very commonly seen faults, and what to look at first before going after a gremlin that may not exist at all. You are going to need access to repair information that is very specific to the model you are looking at.
Just knowing the make, model and serial number isn’t enough. Since VW imports vehicles produced all over the world, you will need to know what you are working on. Locate and write down every scrap of information (see Photo 2) you find on the car you have, and precisely match that with the repair information, or you will be going down a lot of dead ends.
Photo 2: There are a number of scanners on the market that are capable of accessing VW codes.
Some of the qualifiers for repair information are obviously model, engine size and date of manufacture. For VWs, add country of manufacture, engine and transmission code, accessories installed and sometimes a sub-model classification like GL, GLS or GLX, as these may make for significant differences in specifications, wiring diagrams and component locations.
Just relying on engine tags isn’t always the best policy either. Especially with the late-model turbo engines where cylinder head replacement has become commonplace, and the mixing of engine codes (marked on cylinder head) and models doesn’t always match. Having accurate vehicle history is great, but often isn’t always available. This is where patience and experience pay off. Always take the time to “certify” the car you are working on. Look for obvious signs of replaced components (see Photo 3), repairs or damage, and work from there.
Photo 3: Every little bit of information can be useful for diagnosis. This ECM was found in a car built before the manufacture date of the module!
So many times, I’ve seen techs take off on a wild goose chase looking for a fault without first checking the basics. Cars with dead batteries or faults that were generated by a battery disconnect will require some additional steps to get the car back to a starting point for diagnosis. Battery condition and charging state is crucial for diagnosis and repair. If the car comes in with a dead battery, or loss of electrical power, charge the battery before doing any other diagnosis, and don’t rely on a jumper to provide the necessary power to sustain any involved testing.
One often-overlooked step on VWs is checking the fuses. Especially on these late-model cars where there are numerous fuse panels (see Photo 4) and other protection devices. For models with the fuse panel on top of the battery, a thorough inspection and testing of the output circuits is needed, as melted connections are not always obvious. Test fuses with a circuit tester rather than just visually, and also look for missing fuses. If a fuse position has terminals for input and output, chances are there should be a fuse there.
On VW models as far back as I can remember, one of the most common problems has been the ignition switch. In doing a basic inspection for stalling, intermittent or inconsistent problems, that is the first stop for a problem. So many things can go wrong if the ignition switch (electrical part) is bad (see Photo 5). Since you have to turn on the ignition to start any diagnosis, just wiggle the key a little and gently turn it against the detents to make sure it is up to the task of powering up the car. A front counterperson who sees the customer remove the ignition key from a 5-pound wad of stuff can give you a heads up on this one.
Photo 4: Basic diagnosis should start by locating and checking all the fuses.
On today’s models, security systems are installed on almost all models and are wired into the car as an integral part of the diagnostic and CAN system. From multiple or lost keys to dead batteries in remote controls, it doesn’t take much to cause these systems to misbehave.
A good place to start with suspected immobilizer faults is by acquiring all of the available keys for the vehicle and making an attempt with each. An aftermarket security system installation can cause significant problems since some of the factory system will remain and may not be compatible with the aftermarket piece. Some of these systems can work for awhile and then go crazy when just the right set of circumstances causes a shutdown of the car’s systems.
An easy diagnosis starts with acknowledging the installation of an aftermarket component and questioning the customer on the timing of the fault and the installation of the new equipment.
Photo 5: How is this possible? The engine is running, but no gauges, no charging. Obvious ignition switch fault.
For the basics, one other item can be considered. Like your PC at home, the communications network on a car can get stuck or “lock up” due to a piling on of faults or improper operations. Performing a “cold boot” on the entire car (when nothing else works) should be a final step in eliminating communication problems before going into a more in-depth diagnosis.
COLD BOOT PROCEDURE:
1. Disconnect both battery cables.
2. Momentarily touch the cables together, then separate and insulate.
3. Wait 15 minutes or more before reconnecting the battery (good time to recharge).
4. After restart, shut down and perform the basic settings for throttle control module. Throttle basic settings must be made on a cold engine.
5. If the car still won’t communicate at this point, diagnosis with the proper equipment is necessary.
This same type of reboot procedure can be done for a number of control modules by disconnecting them, allowing them to power down completely (disconnected for 15 minutes), and then reconnecting and restarting.
TESTING PROCEDURES
A good part of the operating costs for any auto repair facility is the tools needed to stay current with newer models. In addition to specialized tools for mechanical work, the cost of repair information and testing equipment today makes it imperative that you know what models you are going to work on and specialize in.
For VAG cars, basic diagnosis can begin with a generic scanner, but once codes are pulled, or the battery is dead or disconnected, a VAG-compatible scanner is needed to perform the necessary resets needed, as noted above. A compatible scanner will have the functions available for performing “basic setting” operations. Checking various system components through measuring blocks will also help in pinpointing problems when some sensors are out of normal operating range. Scanners without measuring block capability will not allow you to check for zero or basic settings for a number of components, like the transmission, steering and ABS.
A digital volt-ohm meter (DVOM) is needed to get into component and wiring diagnosis. A collection of probes and non-invasive connectors to test the various circuits is handy. A circuit tester that can test and provide power for circuits is a valuable tool.
TEST FOR AFTERMARKET INTERFERENCE:
1. Using a DVOM, test for battery power at pin 7 of the Data Link Connector (DLC).
2. If FULL battery voltage is present, the K-line or communication circuit has been compromised. A reading of 2 to 10.5 volts is OK.
3. Check for installation of aftermarket accessories.
4 If there is an aftermarket radio installed, remove and inspect the electrical connections at the black (OE) electrical connector. Pin 3 of this connector is the communication line.
5. Eliminate any possible power from this circuit from the new radio. Remove the wire from the connector or clip the wire and tape the ends.
6. For other aftermarket installations, you will need to test for battery power sources and eliminate them before any other diagnosis can be done.
7. Recheck for a proper reading at the DLC, pin 7, (2 to 10.5V).
Remember that since these cars use a CAN circuit that connects all of the various control modules on a single communication line, any interference can be a problem, and it can come from any component that is incorrectly wired. You will need pin-out locations for the various modules to know which pins are used for the DATA line.
BASIC SETTINGS
After resolving communication faults on a VW or Audi, certain steps must be taken to re-establish the basic settings of components before a restart. The main one that comes up routinely is the Throttle Control Module basic settings. The purpose of this step is to confirm for the ECM (and through the CAN data system other modules), idle and wide open throttle positions of the accelerator pedal and the throttle body. Since most 2000 and newer models are totally drive-by-wire, this is a critical test and confirmation for safety and control. This procedure is required any time there is a battery disconnect, throttle body replacement or removal, or ECM disconnect.
Here is the shortened version of the setting procedure:
1. Visually inspect the throttle body and clean, if needed. There are cautions about the use of any spray cleaner that might get into the throttle body module and damage it. It’s better to just spray cleaner onto a rag and wipe it by hand.
2. Make sure that the throttle plate operates smoothly and freely through its entire range. On models with a cable attached to the throttle body, make sure the cable is properly installed and there are no modifications that would prevent completing the test (see Photo 6).
Photo 6: A close look will show the paper clip holding the throttle plate open so the car would idle. This will prevent basic setting from completing.
3. Clear any remaining codes. Key must be on, park brake set and auto trans in park or neutral. Keep your foot off the brake and accelerator pedals.
4. Depending on the scanner and the language used for basic settings, go to ENGINE (01) and to Function 04 Basic Settings.
5. Throttle basic settings are displayed in either group 060 (most drive-by-wire models) or 098 (cars that have a cable attached.
6. Once you have selected the proper group, again depending on the particular scanner, the test will auto run or press enter.
7. The forth line in the data screen should display “ADP RUNS,” and after the throttle opens and closes to determine its range, it will change to “ADP OK.”
8. At this point, you need to back out of the adaption screen, turn off the ignition for a minute or so, and restart the engine without touching the accelerator pedal.
9. Road-test the vehicle, noting that the throttle is working correctly, and then recheck for faults. The readiness flags will not be completed until the car has been driven through a complete drive cycle.
FINISHING UP
This is just a small clip of possible communication scenarios for VW and Audi cars. If you come up against one of these cars that just won’t communicate, take the time to get to know it better, ask some simple questions at first and then start narrowing the problems by eliminating the obvious ones. It works in life, so it should work with a car!
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