Special Considerations for Round 2 Diagnostics
A lot of the hardest diagnostic jobs come in the form of a vehicle that has already had one, two, or three other people work on it. Sometimes from another shop, sometimes over a period of weeks. Here are some helpful things to keep in mind when trying to fix these cars in a profitable time frame:
Always be twice as thorough with your testing, if it was an easy car it wouldn't have advanced to Round 2.
Always review the work previous technicians have or may have done early in your diagnostic process, some particular things to look out for:
Fuses: make sure all fuses are present and of the correct amperage. Sometimes you may find that a higher amperage fuse was installed to keep a short circuited component functioning and this can mask the problem. Other times someone pulled a lot of fuses at once and mistakenly didn't reinstall them in the correct locations. For example, when trying to identify the circuit causing a parasitic drain. Another scenario is that fuses were pulled and simply never reinstalled. Missing fuses can also be caused by replacing fuse carrying parts that didn't come fully loaded, which brings me to my next point;
Bad parts: Inspect any and all parts that have been replaced on the vehicle, chances are very high the car had one problem and the attempted repairs added a second problem. If control units have been replaced they may not have been programmed, coded, adapted, taught in, initialized, etc. That could be all you need to do to get the job done! Procedures vary by application but it's not uncommon that a shop replaced an ECU without realizing it needed configuration, and without knowing that their tooling could not perform the task. Another thing that can happen is that improper replacement parts are installed, typically in an effort to save money. It could be failed Remanufactures, random ebay parts, used parts from a different type of vehicle, poor quality aftermarket parts, junkyard parts, or customer supplied parts. A common scenario is that repairs 1 through 3 failed to fix the vehicle and as the budget dried up the quality of the parts deteriorated.
If at all possible, avoid compromising your diagnostics with "money saving" shortcuts.
On a Round 2 car, you can't afford a whole lot in the way of risks and half measures. One of the most destructive forces in diagnostics is doubt. By using parts you aren't confident in you introduce another variable that will nag at you and eat away at you as you move forward. Undermining your logic, dividing and conquering you. You need to divide and conquer the car, not the other way around. In the worst case scenario there is something unique about the OEM part, it is the only one that will fix the car, and it can't be conclusively proven. Have seen this with alternators and some other items. On rare and frustrating occasions, the dealer part is bad. RARE, but NEW does not equal GOOD, even when it comes from the dealer.
Those shortcuts don't really save anyone any money in the long run, what they are most likely to do is to cause your shop and you as a technician to subsidize the repair of the customer's vehicle with your time and money. When it comes to responsibilities, you didn't buy it, build it, or break it.
My preferred method to deal with Round 2 vehicles is to return them to as close to the original state and configuration as possible early on and to get a very good description of the original customer concern.
Sometimes this can't be done because parts have been lost, thrown out, or given up as cores. On the off-chance that you can speak with technicians who worked on the car previously it's a good idea to talk about what they observed, what they did about it, and why. Keep any information provided in mind but don't adopt anyone else's conclusions or fall into any assumptions. In many cases an excellent technician worked on the vehicle but his or her approach was not suitable for the problem. Follow their tracks but don't follow in their footsteps. Don't let anyone dictate your decisions, and that goes for service advisors and customers as well.
RELAYS! Relays, Relays, Relays! CHECK THE RELAYS! A frequent troubleshooting technique is to swap relays around to search for a defective one. Most commonly similar looking relays are identical in form and function. In SOME CASES there are FIVE PIN relays mixed among the others and when these are placed in the wrong spot they can cause extremely bizarre short circuits depending on how they are designed, normally open, normally closed, one contact, two contacts etc, and depending on how the fuse box is wired. Cruelly there are sometimes unused circuits wired into cavities in the fuse box (perhaps related to equipment). One of the worst vehicles I have ever encountered had an immobilizer system that communicated over a five pin relay when the contacts closed. The vehicle was in a front end collision and when the body shop couldn't get it to start they unknowingly swapped that five pin relay with a four. The no-start was caused by leaving the key on, burning out an electric pump for the transmission that disengages the clutch. Confusing things - the attempt to solve a no crank condition was followed by a -repair- that added an identical no crank condition. Problems caused by relay mix ups are vastly complicated by poor schematics in the OEM service information.
Lastly, connectors. Make sure all connectors were installed correctly, fully seated and fully locked in. If wires have been repaired or replaced verify the connections are good (physically intact and minimal voltage under a load appropriate for the wire gauge), and that circuits weren't crossed. Sometimes a connector is water damaged and a replacement is soldered in. This is prime time for connecting the red/green wire that needs to go to terminal 7 to the red/green wire that goes to terminal 39 instead. If there are butt connectors, replace them with solder joints. If a connector has been repinned, assume the terminals were placed in the wrong positions. This is most difficult to spot if there are only two wires going to the connector, it will look correct. Sensors will not function correctly if the polarity is reversed. As an example, an impact sensor is ripped off during a collision and a replacement pigtail is not available, the wires and connector shell are manually assembled... whoops!
Take a close look at the terminals and perform terminal tension/pin drag tests with the correct probes. Most technicians don't have the proper tools for doing this and many are just not aware of the importance of it. The shop should provide this tool! You may find terminals that are related to the problem badly spread and loose. These can create poor connections (voltage drop) especially on power and ground circuits, as well as intermittent connections, the most unpleasant of which are those that are intermittent because they are on the engine and subject to its vibrations.
Ultimately if another technician worked on the vehicle and caused frustrating problems for you, try to forgive them. By design, the industry often doesn't support, encourage, or properly compensate technicians who want to advance in diagnostics...
but isn't that the reason we gather here on Diagnostic Network?
Andrew, You brought up some very good points, For close to 20 years, my mobile diagnostic business mostly followed up behind the factory Field techs and troubleshooters. There were way too many times where the basics were MISSED. e.g. Bad cell in a battery, wrong battery for that vehicle or undercharging alternator. Also, when a vehicle returned back for the same original concern, was the last
Perhaps the words "check" and "checked" need to be removed from our lexicon. One guy reads "check the connector" in the flowchart/trouble-tree and he goes and looks to see if the connector is there. A more knowledgeable tech knows to look-up the terminal size, drag-test, and also to pull the wires and see if they stre-e-e-e-tch.
As a mobile technician I am almost never the 1st hands in. I never ever look at what the previous tech did. I always start my diagnosis at the beginning. In over 50% of the cases it is a basic problem that was overlooked. I always start with the basics depending on the system. I am also not mislead by codes. I check the codes, I refuse to focus on the codes. I test based on data PIDS not codes…
Indeed, all of the basics and routine still apply to a job like this which is why I've titled it "Special Considerations".
Sam, that's good advice. I have taken classes with Bernie Thompson where he also stressed focusing on the symptom, not the code, unless the code is the symptom. In other words, there is no symptom except the code.
I have been in the mobile side for little over 8 years, I agree with some others that well over 50% or more of the time the cause of the problem is in the basics being missed or done wrong. The fact that it is "round 2" or more many times means that taking a fresh look , start from the beginning means fixing the other problems that the other mechanics had created. This means staying focused when…