Over 32 Years Of Automotive Transmission Diagnostics

Knowledge is power, and sometimes just knowing where to find that knowledge is all it takes.


    Being in the transmission industry for over 32 years whenever I'm dealing with a problem I'm always saying to my self. "I know I've seen a bulletin, seminar presentation or tech magazine article on that problem somewhere. After wasting countless hours searching for the technical material I was looking for.  I decided to make a list of all the bulletin, seminar or trade magazine articles so I could quickly look up the location of technical material whether it was for rebuilding or diagnosing a transmission problem.


  Trans Tech Index is just that a list. A way of finding the correct technical material that we need when we need it all in one index. This will save diagnostic time which saves money.

    I use it everyday while doing calls on the ATRA technical hot line. It makes it easier and much faster to look up the bulletin, seminar page or tech article to fax or email to the technician to fix their transmission problem. While working for ATSG, myself and some of the other hot line technicians used it to diagnose and fix transmission problems daily and still do.

    To stay ahead in this industry you must read everything and anything technical that you can get your hands on. The two magazines links located on the left side of this page are a must. You can just click and go to their website and read them both for free every month and download them onto your computer. One other magazine I would suggest (not listed) is Motor Magazine. This can be found in the Trade Links page, as well as many of the top automotive industry's technical service, transmission parts and specialty product suppliers. Just click on the icon and visit each website. Because of all the electronics on the other side of the flywheel that cause a transmission to not function properly, is a good reason to learn all we can about what's going on with the engine performance.


    Attend any and all seminars that come to your area and even those you may have to travel to. It's you're future that you are investing in. The amount of money spent attending any seminar where you will learn something that will prevent a comeback or a won't leave is priceless. If you prevent the cost of one comeback from that knowledge, it pays for the seminar.


    The information obtained in books and/or CDs from seminars and technical magazines has unlimited value. If you organize that information and categorize it in neat and orderly fashion for future reference; you will save more time making money fixing vehicles rather than looking for the fixes.


    25 years ago we had no problem remembering most of the fixes off the top of our heads. Back then there were less transmission models and vehicles then there are today. Never mind the fact that when we get older and remember less, or at least I do. With a well stored data base and a program like Trans Tech Index, it will make finding that information as we need it when we need it. This alone will save you the time fixing one vehicle, to free up time fixing and making money on the next one.   


    The best way to build a technical data base that you'll need in today's market is through companies like ATRA (Automatic Transmission Rebuilders Association), ATSG (Automatic Transmission Service Group), (just click on the links to the left to visit their websites) RatioTek, Transgo, Rockland Standard Gear and many others.    


    There are several internet technical forums like TRNW (Transmission Rebuilders Network Worldwide) that are inexpensive and very helpful. TRNW is a network of hundreds of transmission techs across the world working in transmission shops everyday that just may have the answer to your transmission problem. No I do not get a commission for promoting their product, it's just free advice. iATN (international Automotive Technician's Network) is a free forum that covers all automotive repairs. Just to name a couple that I use daily, I subscribe to several.


    You would be amazed on how much information there is on the internet for free. Remember what I said about Gears & Transmission Digest, now you can start your tech magazine data base.  If your looking for tech of any kind just Google it. 


    The key to surviving with the rapid changes coming into the transmission industry today is being able to diagnose any and all computer or electronically related transmission problems. Many times those problems can be caused by something on the engine side of the flywheel. Let's face it we can build a great transmission but if it doesn't work someone has to diagnose it. If the guy down the street can't fix it then the customer will eventually come to you. Your reputation for fixing vehicles other shops give up on or turn away will travel further than you think.

Diagnosing & Troubleshooting Automotive Computer Controlled Transmissions

    The first step in diagnosing electronically controlled transmissions is to first learn how they work. It's like when we grow up we have to learn to walk before we can run. When you figure out your first really tough electrical diagnostic problem it will begin to hit home just how easy it can be when you understand how it functions.


    Diagnosing and troubleshooting automotive computer controlled transmissions will always have a place in the industry, no matter if their electronically controlled CVT or Hybrid transmissions. The more you learn the easier it becomes to understand how they function, which takes the fear out of diagnosing electronics.


    One of the major things to know about doing any automotive diagnostic & troubleshooting service is to understand what the Diagnostic Trouble Codes (DTC) is trying to tell us.


    Many times on Ford vehicles a misunderstanding of what the code is saying will lead to an incorrect diagnosis. This will cause hours or wasted time chasing a ghost. For example when you get a TCC code P0741 in a Ford vehicle it is not electrical it is a slip code. Changing the solenoid may fix the problem but there are several other issues that will set the code, from valve body and/or bushing wear to restricted cooling systems. Not excluding a bad torque converter. A diagnostic code P0743 is definitely electrical although you may think it should set a code on start up but may not set the code until the TCC clutch is commanded on.


    Many import vehicles such as Hyundai use the same code for a solenoid whether it's a mechanical or electrical failure. The easiest way to distinguish between the two is this; if the code sets on start up, it's electrical and could be anything from the computer system to something as simple as a short in the wiring. If the codes set only after driving the vehicle and a malfunction occurs such as a missing gear, slip or flare; then the computer system is trying to say "Hey I told that solenoid to do something and the results I'm seeing (ratio error) are not correct" so the Powertrain Control module (PCM) or Transmission Control Module (TCM) turns on the Malfunction Indicator Light (MIL) and sets a fault code in memory.


    This is just a few of the scenarios that can be expected when troubleshooting today's transmission whether their in domestic or import vehicles. The big "3" used to be GM, Ford & Chrysler and many shops event to this day refuse to work on imports. With many of the newer transmission models being used in several different vehicle types made today. Such as Dodge rear wheel drive vehicles using a NAG 1 (722.6), no not your ex-mother in law. This Mercedes built transmission can be found in many Dodge vehicles. Mitsubishi and Chrysler have shared front wheel drive transmissions also. The 41TE (A604) can be found in Mitsubishi cars for example.


    GM, Volvo and Nissan all use the AW55-50SN. In a GM it will be referred to as a AF33-5, in Volvo as an AW55-50SN and Nissan calls it an RE5F22A. There are some important technical differences that you need to be aware of when trying to exchange parts. Ford's new 6R60 is in reality a ZF6HP19 as well as GM's 6L80 using the same technology from ZF.


    So the big "3" in today's aautomotive transmission market is referred to as "Domestic, Asian & European". When attending a seminar don't pick up and leave after lunch break because you don't work on imports. The information you learn on imports may also be in the domestic vehicle that just might show up on Monday.

Diagnostic Automotive Transmission Service

    My first thought on this subject is tooling. I know what you're thinking Digital Volt Ohm Meter (DVOM / multimeter) or an Oscilloscope (everyone hates that one). No, I'm talking about diagnostic tools like scan tools or laptop scan software for communicating with today's automotive transmission electronic control systems. Re-flashing is good also but that's another story all on its own. We'll get into that later in time.


    To perform any type of automotive transmission diagnostic service without the proper tools would be the same as removing an all wheel drive transmission out a Land Rover Freelander with hammer and chisel. It can be done but it won't be pretty and just how long will it take. You can always do the shot gun approach; blast as many parts at it to get the vehicle out the door. We were talking about saving time and money weren't we?


    The first question everyone asks is "What do you suggest"? I don't promote anyone's particular product over another. All I can suggest is what you can and can not afford to be without. If your scan tool is out dated (no matter which one you can financially afford) then it's time to bite the bullet and get it updated. All scan tool companies have problems. There is no inexpensive one size fits all scan tool in the automotive after market. At times it may be difficult to access the information that is needed to diagnose transmission problems using an after market scan tool. This is the problem for any after market scan tool in the automotive industry today. So before you blame the scan tool you're using, here is why it is what it is.


    Laws and agreements were established for all O.E. (original equipment) automotive manufactures when OBDII started back in 1996. The laws state that manufactures have to standardize code designation, device and/or component names, as well as diagnostic connectors such as the DLC (data link connector) pin identification and location; to gain access to all codes, data or service information pertaining to emission controls for the automotive after market. Back in 1996 approximately 90% of the information that the after market shops needed to repair vehicles was available. In todays automotive after market, it's a different story. On some European import vehicles it's about 10% availability.


    The laws also state that the manufactures can have their own code designation and information for the systems that do not effect emissions. Such systems as HVAC (heating ventilation & air conditioning) airbags, security systems, and (that's right) transmission systems to name a few. Also stated (this is the bad part) is that manufactures do not have to release any of this information to the after market industry. This is where manufacture specific codes, data and bidirectional controls are only available with O.E. scan tools for those systems. 


    Most after market scan tools can access the non emission control systems depending upon the information purchased from the O.E. or obtained by the after market company through research. Some information is not made available due to safety issues and the O.E. manufacturer does not want to be held liable.


    While using a GM Tech II on a 2000 GMC truck with an Allison 5 speed transmission to diagnose a no move condition. The PRNDL lights would flash when the transmission was shifted into gear indicating a problem when the vehicle didn't move. No codes present and all the scan data information looked normal. When a GM technician was asked about this problem he didn't have an answer for it. To make a long story short a 50 cent screen in the valve body was restricted.  So there you have it, every scan tool manufacturer has issues and problems.


    The only way it was diagnosed was by knowing how the transmission worked, which led to the valve body. How to know that, simple..........READ! Remember what I said about tools, that includes transmission technical manuals and magazines. You can't fix it until you know how it works. I'm no rocket scientist; I just research how a particular transmission, computer or electrical wiring system works so I know what to check and what doesn't need to be checked. Hmm, there's that saving time and money thing again.


    When diagnosing automotive electronic problems whether it's on the engine side of the flywheel or not. We're not only talking about codes and wiring but vehicle computer systems in general. You don't have to remember everything you read, just store it somewhere so you can look it up later. I'll probably forget what I wrote on this website tomorrow, but I can click on it anytime to remind me.


    Someone once said to me, a good technician has a great memory and knows what the fix is off the top of his head. I may have agreed with him 20 year's ago. Today the truth is, a good technician knows where to look up the fix, and having an extensive technical data base to find his answer. This is where I shamelessly plug Trans Tech Index to know where to look up the information in that data base in a quick and timely manor. Thanks!

Teaching How To Diagnose & Troubleshoot Automotive Transmission Electrical Problems

    I like to use typical everyday shop problems and fixes as examples when presenting a seminar to get my point across. Along with a power point presentation that has some humorous references and visual affects to keep the techs attention on the presentation and not on me. So that their not just listening to or watching some guy reading out of a book. Shop war stories so to speak. I try to make them fun to listen to and when you're having fun learning we retain the things we learn better. I know I've seen that written down somewhere. No, it's not listed in my Trans Tech Index.


    That's not the only reason I do it. We can all agree that transmission tech is boring and sitting in a room for 6 hours or more on a Saturday. Especially after partying half the night before and eating a nice big lunch doesn't help. When I can make the seminar attendees laugh I accomplish three things; they're enjoying the seminar and paying attention, retaining the knowledge presented to them and waking up the techs that fell asleep. See, you at least smiled on that one.


    With that being said here is typical problem that may at first seem not too typical when presented. I received a call from a local transmission repair shop near by that I often go to get my hands dirty and keep my diagnostic skills sharp. Another shop further away had been working on a 2000 Lexus RX300 with a U140E series transaxle for more than 5 weeks. The customer is in a rental car paid for by the shop in question. Needless to say the shop is frantic at this point and sent the vehicle to this shop and asked me to look at it.


    The vehicle had a Crank Sensor code and the transmission would bind and shuttle in and out of gear during the 1-2 and 2-3 shift. 4th gear shifted fine. It was at the Lexus dealer for a week and they basically gave up on it. The car went to another local transmission repair shop known for doing electrical diagnostics. After a day or two decided they didn't have time for it and sent it back to the original shop. Original shop now tried the shot gun method 2 Crank Sensors w/o checking the sensor signal. Then 3 valve bodies, although the PCM was commanded this shift pattern. Another complete transmission and you get the picture by now.


    The next thing that was said was "Are you sure you want to get involve with this nightmare". At this point I thought "WOW" this should be interesting to say the least. What do I have to lose; I don't own the car besides that mine drives fine. The first thing noticed is the computer is removed from the retaining bracket behind the glove box and lying on the passenger floor for easy access. Cool, less work for me. It was still connected to the PCM but several wires had small pieces soldered into them from several other techs back probing and had to be repaired. It looked like a porcupine rolled around in bed with it. I'll admit I did have second thoughts at this point.


    The way the transmission shift pattern is commanded by the PCM is this; both shift solenoid SL1 and SL2 are turned on for 1st gear. SL1 is turned off during the 1-2 shift and SL2 is turned off for the 2-3 shift. The S4 solenoid is turned off for 4th gear. The PWM SL1 and SL2 solenoid signal from the PCM is Pulse Width Modulated (square wave). The S4 solenoid is an on/off type. A Snap On Vantage was set it up like a breakout box to read two graphing screens to monitor both the SL1 and SL2 solenoid square wave form. Knowing how the system works it was time for the road test.


    During the 1-2 shift the PWM SL1 solenoid turned off with one voltage spike (normal). Then it started pulsing on and off again and that's when the bind and shift shuttle is felt (not normal). Then the SL1 solenoid turned off completely only after shaking the dash violently for a couple of seconds. Then the vehicle drove smoothly until the 2-3 shift was commanded. The PWM SL2 solenoid turned off, then the SL2 and the SL1 both started pulsing erratically at the same time almost causing the tires to bark. This was extremely abnormal and after just one block of driving it was time to head back to the shop. No one would drive this vehicle too far in this condition.


    Back at the shop the hood was released and one of the installers was asked to unbolt the alternator feed wire from the battery. On the next test drive at the same distance it had the same problem. Back to the shop the hood was re-opened just to have a look see. It was noticed that the installer did not unbolt the alternator feed from the battery he only unplugged the field connector. With the connector plugged back in and using a 10 mm wrench to unbolt the battery feed to the alternator and road tested again. On this road test the transmission shifted normally. The vehicle was stopped and the battery feed wire was bolted back onto the alternator and the symptoms reappeared. Great, we're almost there. Now one of the red leads on the Vantage was moved over to the ground circuit of the PCM, testing for a voltage drop.


    Electrical theory for any ground circuit is this; there's always source voltage on the ground side of every load device, whether it's a solenoid, fan motor or a light bulb until it's grounded (even a computer). There is always residual voltage left on every ground circuit when grounded. Normal residual voltage on any ground circuit should be no more than .1 to .2 volts. Some factory manuals say as much as .3 volts is ok, but at that point I don't trust the ground circuit. If 0 volts is seen, the meter lead is not making good contact with the circuit being tested or the meter isn't grounded correctly. The multimeter should always be grounded at the battery even if you have to run a lead from the battery to the meter. When doing a voltage drop test on the ground side of any circuit it should read approximately .02 - .03 volts or more (meter dependent).


    Sure enough there was .8 volts showing, way too high, A temporary ground was jumped from the battery to the PCM. On the next road test the vehicle performed perfectly. A redundant ground was run to the PCM and the vehicle was fixed. Total amount of time spent diagnosing the vehicle was about 25 minutes. To this day the original shop does not believe the vehicle was fixed in that short time period. Then again, that's why it was at this shop for diagnosis and not theirs.


    Oh yeah, that Crank sensor code also went away. When this vehicle’s electrical system was researched the wire schematics verified how the ground circuits worked. It was found that the Crank Sensor and the transmission Input (ISS) & Output (OSS) speed sensor along with the vehicle computer, share the same shielded ground at the back of the Intake Plenum. This ground location is impossible to see even with a mirror.


    Knowing how basic electronics work (remember I'm no rocket scientist) led me to a ground problem with the alternator disconnected. Electro Magnetic Interference sometimes referred to as A/C ripple is a big problem with speed sensors. We get that problem everyday on the ATRA technical hot line. There is always some A/C ripple coming off the alternator even when they are working fine. If the shielded grounds on any circuit have connection problems they become radio antennas and pick up that interference. That's why the crank sensor set the code, although the speed sensors didn't. That would have been too easy if they did. Now wasn't that more pleasant to learn about doing voltage drop test on grounds and A/C ripple than the old fashion way................boring Zzzz.


    Final note: When removing and installing a transmission on this vehicle, the engine has to be tilted at an unusually sharp angle. Now you know, (the rest of the story) how the ground wire can become loose or broken during a transmission repair.


    What we need today in the average transmission repair shop to perform efficient professional work in the electronic world of automotive transmission diagnostics, rebuild or repair is:


Technical Diagnostic & Troubleshooting Automotive Transmission Skills

A Reliable Technical Data Base (CDs/Computer Software/etc)

Technical Transmission Diagnostic & Repair Manuals

Up To Date Scan Tools Or Computer Scanning Software

Up To Date Electrical Testing Equipment

Knowledge Of Automotive Transmission Computer Control Systems

Easy Access To Computer Systems Information (Mitchell's/Alldata/etc) 

Knowledge Of Electrical (Codes/Wiring etc)

Knowledge Of Automotive Transmission Mechanical & Hydraulic Systems


    A great source for all of this information can be found on the internet through technical service providers such as ATRA, ATSG (to name a couple) or just plain searching the web. Check out the Trade Links page.