Jim Warman Posted November 11, 2010 Share Posted November 11, 2010 I wasn't sure where to post this.... <2580 - 2011 F-SUPER DUTY 6.7L DIESEL ENGINE, MIL ON WITH DTC P0884 SOME 2011 F-SUPER DUTY VEHICLES EQUIPPED W/ 6.7L DIESEL ENGINE AND 6R140 TRANS MAY EXHIBIT A MIL ON WITH DTC P0884 SETTING IN TCM AFTER A REFLASH. THE CODE INDICATES THAT AT SOME POINT, VOLTAGE TO TCM WAS LOW WHILE TCM WAS IN OPERATION. THIS COULD HAPPEN DURING THE REFLASH IF VEHICLE WAS NOT ON A BATTERY CHARGER. IF THIS CODE SETS AFTER REFLASH, RECOMMEND STARTING THE TRUCK AND ALLOWING IT TO RUN TO GET THE CHARGING SYSTEM REPLENISHED, CLEAR THE CODE AND THEN SEE IF IT RESETS. IF IT DOES RESET, LOAD TEST POWER AND GROUND CIRCUITS TO TCM. IF THE POWER AND GROUND CIRCUITS ARE OK, INSPECT TCM. IF A POWER OR GROUND CIRCUIT CONCERN IS IDENTIFIED BY LOAD TEST, REPAIR CIRCUIT IN QUESTION AND RE EVALUATE. IF THE CODE DOES NOT RESET, NO FURTHER DIAG OR REPAIR IS NEEDED. REFER TO WSM SECTION 307-01B FOR ADDITIONAL INFORMATION. > Is Ford finally getting wise to the proper way to test circuitry? Will they, some day, instruct the tech to perform a volt drop test correctly? Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 11, 2010 Share Posted November 11, 2010 I take it you are bringing attention to the fact that Ford is asking us to LOAD TEST circuits here and not use our ohm meter or volt meter??? How many techs to you think actually know how to load test a circuit and interpret the readings? Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 11, 2010 Author Share Posted November 11, 2010 Yes.. I thought it quite remarkable that Ford didn't have us test open circuit voltage and ground integrity with an ohmmeter. (Let's remember that the last step of nearly every pinpoint test is "replace the module" and Fords 'traditional' power and ground test almost assures needless replacement). As for the lack of understanding or confusion over one of the easiest electrical tests known to man (the volt drop test), I can only shake my head in wonder and continue to try and teach the young'uns. I mean... Kirschoffs principles are pretty much constant and unchanging, right? Musicians spend their own "personal" time practicing their instruments.... racers spend their own "personal" time improving their knowledge and reactions.... pilots - same deal... Techs? After work most of them go drink beer. With a few bits of wire, an old battery, an electric motor and a couple of lamps, they could build some practice circuits and introduce bugs to see what their DMM would read. FWIW... something else I missed in the BCM - "IF THIS CODE SETS AFTER REFLASH, RECOMMEND STARTING THE TRUCK AND ALLOWING IT TO RUN TO GET THE CHARGING SYSTEM REPLENISHED". Most aftermarket alternator rebuilders will admonish us that the alternator is not a battery charger and that we should use a battery charger when necessary rather than have the alternator do the work... Hey - I'm just repeating what I have seen. If we don't use the battery charger, it may become necessary for the SA to look a customer in the face and say "we will bring your expertly repaired truck to the front as soon as we jump start it... and please don't shut it of for a couple of hours". Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 12, 2010 Share Posted November 12, 2010 Quote: Ford is asking us to LOAD TEST I like to call it the "burn your fingers and blind your eyes" test. Quote Link to comment Share on other sites More sharing options...
GregH Posted November 14, 2010 Share Posted November 14, 2010 Over the last few years I've been taking Ford's online web based training. Up until this point, I'd only taken the minimum to remain diesel certified - but our dealer pays us the average completion time, so we've been taking advantage of that on slow weeks. I remember in the automotive fundamentals section an electrical class that had us follow a pinpoint test - and needlessly replace a module based on power or ground circuit tests that passed with a DMM. The class then brought it around to demonstrate that a better way to test it is a load test. There were various voltage drop tests performed during the class, too. Basic electrical classroom also addresses these things. The proper methodology is being taught. It is up to us to retain it. Granted the pinpoint tests will ask for inappropriate testing procedures - a ground circuit with 4.8 Ohms passes? - so we have to follow the correct procedure for the circumstance we find ourselves in. We have to use our brains.. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 14, 2010 Author Share Posted November 14, 2010 Something our Edmonton instructor re-affirmed for me. When using PPTs, we need to look at what the terst is asking us to prove or test... and then use the best test for the task. Using one of these.... and a DMM, you can determine if the problem is the load (or device being driven), the power supply of the ground with 3 volt drop readings. Two things most techs will overlook... you absolutely need to measure battery voltage before you begin volt drop testing - if you don't know what voltage your system is experiencing, what are you measuring... (I always recommend either a fully charged booster pack or a "clean" battery charger be used and, if diagnosis is taking a while, recheck your system voltage - modules do wonky things when system voltage approachs 9 volts). And all of your readings need to be made "at the battery" if you need either a "ggod ground" or "good B+". The thing that still makes me shake my head.... it is just as easy for a PPT to describe an appropriate test as an inappropriate test... yet they choose to send us down a bad path. Quote Link to comment Share on other sites More sharing options...
GregH Posted November 16, 2010 Share Posted November 16, 2010 it is just as easy for a PPT to describe an appropriate test as an inappropriate test... yet they choose to send us down a bad path. The choice may be more complicated than it seems. Aside from the expense involved in rewriting all the relevant pinpoint tests, you would run into the problem of exactly how to quantify the test. How would you describe load testing a power and ground? Now how would that procedure differ if you were testing power and ground to a VSM vs. an ABS module, with their markedly different power requirements? Now do it using standard tools, with quantifiable results. Now cut out half of the words, and replace them with pictures or icons, for those who lack reading comprehension and for ease of translating into other languages. Then take your draft and get buy-in from the appropriate engineering departments, get it past legal, - ah, you get the idea... Or maybe we should continue to do what we've been doing: Originally Posted By: Jim Warman When using PPTs, we need to look at what the terst is asking us to prove or test... and then use the best test for the task. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 16, 2010 Author Share Posted November 16, 2010 That's the deal, Greg.... a volt drop test is a volt drop test... Whether the circuit is designed to flow one amp or 100 amps - you wont want to see much more than about a half volt drop on a power side circuit or a ground circuit. The idea is to have adequate volt drop across you load or device. If you have unintended resistances in the circuit, current flow will be limited... and there will be insufficient voltage to ensure the operation of the device. Sadly, the way most of us have been "doing it" is neither efficient nor correct... load testing a circuit is better than open circuit volt testing but far too often we test the circuit with a load that doesn't replicate the true operating conditions. Quote Link to comment Share on other sites More sharing options...
mchan68 Posted November 16, 2010 Share Posted November 16, 2010 Sadly, the way most of us have been "doing it" is neither efficient nor correct... load testing a circuit is better than open circuit volt testing but far too often we test the circuit with a load that doesn't replicate the true operating conditions. But you can thank the W.S.M. and the PC/ED for this method that is used by almost every Ford tech. You don't think there aren't times when I don't have a brainfart, about the proper way to test for VOLTAGE requiring the circuit in question to be functioning? Yes Jim, I'm sure I and many other techs probably think this way when diagnosing anything that involves testing an electrical circuit. But the reality is, the W.S.M. and the PC/ED always instructs us to KEY/ON, disconnect C123, check for VOLTAGE between pins #2 and #43. Is VOLTAGE greater than 10 volts? Reading between the lines, that tells me the test is 'asking' me if I have battery voltage on that circuit. Is this the PROPER way to test it? NO, we all know that it isn't. Similarly when 'asked' if RESISTANCE is greater than 10,000 ohms, that to me means the circuit should NOT have continuity, and vice versa when 'asked' if RESISTANCE is less than 5 ohms. What I find interesting is that there is never a test in which we are instructed to check for current flow, or AMPERAGE. Why is that? Is it because the writers of the PC/ED and W.S.M. think that most techs are idiots, who don't know how to connect a DVOM properly to check for AMPERAGE without blowing the DVOM? I think it all boils down to having a 'paper trail' behind us when the end result is a component being replaced without actually fixing the concern. How many of us have run into that type of situation before? At least by following the W.S.M. or PC/ED test steps and documenting as such, is our way of ensuring WE aren't the ones to be held accountable to an unsuccessful repair. Does that make it right? I don't think so, but where else are we to turn to when a vehicle comes in with an electrical concern requiring some 'testing'? More importantly, does the service pub test procedure get updated accordingly when an unsuccessful repair results from following that particular test step? I think at the very least, following the test steps as outlined in the service pubs and being unsuccessful at the repair is a far better scenario than taking the "shotgun" approach, be it on the customers' or Ford's dime. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 16, 2010 Author Share Posted November 16, 2010 Unless you are testing a charging system output, starter draw or parasitic draw, amperage isn't a very good method for diagnosing circuit concerns (certainly, current ramping a device on a lab scope is a viable diagnostic aid for driveability concerns) involving non-functioning loads. Indeed, there is always a chance that a circuit fault could have a circuit drawing design current flow yet leave you with a device that isn't performing as it should. If you have a lamp that doesn't light or an electric motor that doesn't motor, hooking up a ammeter isn't going to tell much other than you have no current flow (if there was, the lamp would light or the motor would motor - at least a bit). Remember, in a series circuit current flow is equal throughout the entire circuit - total voltage drop in a circuit is the sum of all voltage drops in the circuit - and volt drop will be different depending on where it is measured. This is one of Kirschoffs fundamental laws. We can use our voltmeter to find "unintended" or "unauthorized" volt drops that will have us with a weak or slow turning motor or a dim lamp. Volt drop testing is so painfully simple, amazingly accurate yet vastly underused as a diagnostic method.... Quote Link to comment Share on other sites More sharing options...
Keith Browning Posted November 16, 2010 Share Posted November 16, 2010 In my over 24 years of "doing it" there have only been less than a handful of instances where the usual resistance, voltage or voltage drop testing have failed me. The tools required for these types of "tests" are very standard and the expected results can be specified. I think Jim eluded to the the heart of the matter... Since any time we perform a circuit load test the device used is typically fabricated from any number of possible components the results can and will vary especially if we go looking for a specific value. That is why the two requirements for a good circuit load test are 1-provide a sufficient load and 2-is the light bulb bright enough? (pun intended) I don't think that it's the METHOD in which "we" perform tests that is the problem, it's the approach. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 17, 2010 Author Share Posted November 17, 2010 Indeed, Kieth... Labour Op 14200A45 (Wiring repair - Diagnostic PinPoint test) pays a proncely sum of 0.3.... Now... we can fart around doing all manner of goofy shit - or we can take our DMM to the nonfunctioning load and bing-bang-boom, in a matter of seconds (plus additional time for component access), we can decide if we have a pooched load (or device) or if we are chasing a power side fault or a ground fault. We can get on with the business of earning money as we gain access to and inspect connectors, wiring harness and other such mundane tasks... More importantly, should the customer be a retail customer, you can save him money (and impress him enough to insist that YOU do ALL his work) by minimizing wasted time, needless parts replacement and even complete an electrical repair so that you can move onto the brakes and balljoints you might be able to sell. Almost any fiddle player can play a fiddle in the orchestra - only one of them will be chosen as the lead violinist. Side benefit... it makes it look like you know what you're doing..... customers like that for some reason. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted November 20, 2010 Share Posted November 20, 2010 Quote: The idea is to have adequate volt drop across you load or device. I totally agree that voltage drop is the most acurate test of a cicuits integrity. The problem with writing it into the shop manual is, as quoted above, it is no longer a generic test that they can insert into a test and "assume" the reader will know how to perform it, and interperet the results. The shop manual will then have to call out special tools, with specific load ratings, based on the (size of) the circuit being tested. As Keith said, there have only been a handfull of times when a basic resistance, or voltage test have lied to me, but at that point we need to be able to interperet results, and decide if more testing is in order. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 21, 2010 Author Share Posted November 21, 2010 Quote: The idea is to have adequate volt drop across you load or device. I totally agree that voltage drop is the most acurate test of a cicuits integrity. The problem with writing it into the shop manual is, as quoted above, it is no longer a generic test that they can insert into a test and "assume" the reader will know how to perform it, and interperet the results. The shop manual will then have to call out special tools, with specific load ratings, based on the (size of) the circuit being tested. As Keith said, there have only been a handfull of times when a basic resistance, or voltage test have lied to me, but at that point we need to be able to interperet results, and decide if more testing is in order. Oh my God! A volt drop test is one of THE most generic tests there is... Back in the day.. way back before current limiting circuits, ignition coils and starter solenoids were 9 volt devices.... built this way for what should be obvious reasons. Most of the other devices you will encounter on a car or truck will be designed around something closer to 14.5 volts rather than 12. Having said that.... a device will only operate properly if an adequate voltage drop is experienced across the device... Let's try and simplify it... Your system voltage, if the truck is running, should be about 14.5 volts... If it isn't running, it should be (by Fords reckoning) at least 11.5 volts. If you are sane and allowed to vote, 12.6 is wiser and a fully charged 12 volt battery would likely read in the 13.2~13.6 volt range. Now is not the time to get bogged down in tenths of a volt.... However.... and this is where it gets real generic.... in an ideal circuit, you will have about one half volt drop across the positive side of the circuit and similar across the ground side.... The first thing to remember is that you are measuring this shit because there is a problem. Now, here is where I get insulting.... The WSM "assumes " that you are a technician and that, as a technician, you possess the basic skills and knowledge that we assume a technician has.... All that not-with-standing, the fact of the matter is that there is no "special tools, with specific load ratings, based on the (size of) the circuit being tested". With some minor exceptions, it doesn't matter if the circuit flows 2 amps or 20 amps or even 200 amps.... if you aren't dropping near system voltage... SYSTEM VOLTAGE at the load or device, you may have a concern. And, for some reason, you are measuring this. In all truth, I did not expect some of these responses to something as simple as the concept of a volt drop test and I see this as an indication that it is time for some intensive familiarization.... At this juncture, I see too many techs lacking a clear idea of what a proper volt drop test is.... and what volt drop readings are telling them... FWIW, a properly performed volt drop test will never lie to you.... Your method will have you replace the module and then repair the circuit.... Fuck... I wish I was young again... back then, I knew everything. Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 21, 2010 Share Posted November 21, 2010 For anyone still having a tough time grasping voltage drop testing: http://www.vernco.com/sparks/id606.htm This guy has his shit together and it's a pretty funny read. Quote Link to comment Share on other sites More sharing options...
Jim Warman Posted November 21, 2010 Author Share Posted November 21, 2010 For anyone still having a tough time grasping voltage drop testing: http://www.vernco.com/sparks/id606.htm This guy has his shit together and it's a pretty funny read. Jeez... I wish I had written that... a very good read... Quote Link to comment Share on other sites More sharing options...
Brad Clayton Posted November 22, 2010 Share Posted November 22, 2010 Quote: In an earlier life, I was an avionics (aviation electronics) mechanic. It beat working for a living. In the trade, we were known as Coneheads. Here is a little tip for the traveling public: If you see a mechanic with a multimeter heading towards the cockpit, you probably have time to get some coffee. lifted from "chasing sparks" at vernco.com Ah man this guy is too funny. Quote Link to comment Share on other sites More sharing options...
cbriggs Posted November 25, 2010 Share Posted November 25, 2010 Sorry Jim, now that I re-read this post (in a more awake state) It appears I was confused. My reference to special tools and procedures was refering to LOAD testing a circuit... DOH..... No more postng while half asleep. And yes , you are right. The v-drop test is very-very simple and the results are always the same. Quote Link to comment Share on other sites More sharing options...
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