Jump to content

First The Basics - Diagnostics starts with powers and grounds NOT with parts and labor


Recommended Posts

First, The basics
tp.gif    Let’s talk diagnostics.  Do you follow any kind of diagnostic 
procedure, or do you just throw darts on a wall, or play 
“pick-a-part” and hope you fix it before you or the customer 
runs out of cash.  I hope you don’t do that.  That might work 
some of the time, but it’s not a good way to get to the source 
of problems quickly or accurately. 
tp.gif    One of the tire shops that I do business with dropped off a 
2003 F450 with a 7.3 diesel for me to look at. It’s one of 
their service trucks that died on the highway.  
    These guys are super, I’ve known them for years, and they’ve got a great reputation and excellent work force. In fact, I buy all my tires there, and they do all my alignments.  They try to fix their own trucks “in-house” and sometimes, well……the repair/diagnostics are a little out of their comfort zone.  This was one of those times. 
tp.gif    Now, they don’t try to keep up with the scanning or diagnostics on most cars and trucks. It’s a tire shop that specializes in tires.  They stick to what they do best, tires, wheels, and undercarriage stuff.  The only “techy” stuff they get into is with the TPM systems.  Most generally, when it comes to their vehicles they’ll go with the tried and true…”throw a dart and whatever it hits we’ll change.” Of course they’ll ask around first, but you know, second hand information hardly ever gets the job done these days.
tp.gif    They had it at one of their stores in another town for about 3 weeks trying to solve the problem.  When that didn’t work they decided to tow it up to another one of their stores, and see if the guys there had a better dart.  Another couple of weeks and several darts later, all they had were holes in the wall and no truck running.  Then my phone rang.
   “Can you program a PCM on a F450?” the shop asked.
    “No, sorry I don’t do those, but I know who does. I’ll call him and see if he can come over and do that for you,” I told them.
tp.gif    A day or two went by and the phone rang again.  “Hey, this thing still doesn’t start.  The guy that programmed it said it sounded like an electrical problem”.  Ok, somehow, I’m getting involved now.  
tp.gif“Sure, bring it over,” I told them.
tp.gif    Well, they towed it over with a strap pulled by an F250 diesel truck. The F250 looked like a toy truck compared to this behemoth.  With a push and a shove from the F250 the guys got it lined up and into one of my service bays. 
tp.gif    The big concern was the IDM relay, it kept chattering like a machine gun.  Instead of checking codes I thought it best just to start with a complete wire to wire check to determine if there was some lost signal that was causing the problem, or a wire that was scraped and grounding out.  Removing the inner fender on the driver side I could gain access to the Injector module (IDM) and the PCM (Power control module).  Seemed easier to start here than any place else.  It didn’t take long before I tracked down a problem.  On pin #71 of the (new) PCM there should have been 12 volts from the ignition.  No voltage at the terminal.
    Tracing the wiring diagram thru its maze it led back to the in-car fuse box on fuse #22.   I grabbed my test light and checked the fuse… (Rolling my eyes about now) the fuse,… oh man…  the fuse is blown.  Good grief… all this for a blown fuse.
tp.gif     Well, I better change the fuse, and see if it starts. Sure enough; it fired right up… sounded great, good throttle response, and no service lights. 
tp.gif    Now the big challenge, what blew the fuse in the first place?  Following the wiring diagram again…. I traced out all the components on the fuse circuit.  There was one that caught my eye as the likely culprit.  The brake cut-off switch mounted on the master cylinder.  (It’s the one that had the big recall a few years ago.)  
tp.gif    The updated replacement piece was in place but somebody forgot to secure the wires.  The replacement piece has a newer style connector and an adapter connector to allow you to attach it to the original style fastener. Which makes it a little longer than it originally was from the factory.  It was hard to tell where the new wire and connector started, and the old one ended, because the whole thing was lying on the exhaust manifold, and had melted down to a glob of wire and plastic.  
tp.gif    Looking around under the hood there were all kinds of new parts installed. The nicest part……they were all installed correctly. There were no other wires out of place, or any signs of scraps or melted wiring.  The important thing is that it runs, and the truck can go back to doing what it needs to do.  I think the biggest thing that threw everyone on this job was the chattering relay. It sounded bad, sounded expensive… but, all it turned out to be was a loss of proper voltage to the PCM, because a fuse blew from a lead that grounded out. This was due to the improper installation of one small component.  
tp.gif    The PCM couldn’t spread enough voltage and ground signals to all the necessary systems when it was missing the voltage it needed.  As the relay would engage, the voltage drop was too much to keep the relay engaged.  The IDM would pull more signal voltage as the relay would come to life.  Then the PCM would have to drop the ground signal to the IDM relay to compensate for the loss of voltage.  All this was going on very rapidly … on and off, on and off… making the machine gun sound coming from the IDM relay.
     The guys at the tire store were extremely grateful that I got the job done, so they could use the truck again.  For me, it’s another day at the shop.  I’ve got nothing but good things to say about the guys at the tire shop. Hey they tried, I’ll give them that. 
      But one thing I wish they would do next time --- CHECK THE BASICS—BEFORE BUYING PARTS!    It’s cheaper that way… 

View full article

  • Like 1
  • Thanks 1
Link to comment
Share on other sites

Yes, always check simple things(basics) even on what might seem to something so complicated you wonder , will I  be  able to work on this! Gonzo, Another good story I guess from your vault of stories that you have compiled over the years.

Edited by kenk
  • Like 1
Link to comment
Share on other sites

1 minute ago, kenk said:

Yes, always check simple things(basics) even on what might seem to something so complicated you wonder Chee, will I be able to work on this! Gonzo, Another good story I guess from your vault of stories that you have compiled over the years.

yep... busy week... spent a lot of "free" time working on getting the webinar just right and in the "can".   No time for new stories....again.....LOL

Link to comment
Share on other sites

4 minutes ago, xrac said:

First The Basics - Diagnostics starts with powers and grounds NOT with parts and labor.  

That statement should be posted on a banner and hung up in every shop. A car diagnosed (actually not diagnosed but purported to have been) with a bad transmission by another shop was found to simple have a voltage problem caused by a bad battery and alternator. 

That sounds just like one of my old stories... "Shift Happens" were the entire tranny problem was a faulty ground lead because some dork installed a taller battery, and the cable wouldn't reach. So, he cut the chassis ground lead off of the neg. cable and tucked the end under the battery tray.  2 trannys later... I got to work on it.  Unbelievable.  LOL 

Link to comment
Share on other sites

Diagnostics vs parts ... hmmmm sounds like a game played by a lot of mechanics and youtubers LOL... unfortunately parts seems to win out in most shops.. I don't know how many times people look way too deep for the problem.. I guess it is something that we learn as we get better that the basics need to be checked first.. sometimes the problem is right in front of your face but you can't imagine that being the problem so you look deep or in some cases throw more parts.. It must happen in all business or the saying "if it was a snake it would of bit ya" wouldn't of come about. All in all I think we all will be watching or playing in the game of Diagnostics vs Parts, who will win well who knows, but I think we all need to strive to play for the diagnostic team I hard those players seem to last longer and get paid a bit better , and have more loyal fans.


  • Like 1
Link to comment
Share on other sites

While I'm teaching these days we've bugged the practice cars for the students. It's amazing how they ALL jump for a scanner instead of the diagrams to see if the problem is nothing more than a missing fuse.   Even though I stress the basics,  the mere thought of a problem being so simple is over shadowed by the complexity of the systems their examining.   

  • Like 1
Link to comment
Share on other sites

SOOOO TRUE!  My guys are stuck on a misfire, # 3 cylinder was the code.  Can't figure the problem out.   I walked over and said, put the scanner away and diagnose the car from the basics. Verify what cylinder, not what the scanner says. 

Turned out it was #4 cylinder, not # 3 misfire - the harness chewed thru by a mouse.  Back to basics.

  • Haha 1
Link to comment
Share on other sites


How many fuel pumps were condemned due to empty fuel tanks? Back to basics.



I had an Expedition in the other week that had been at a shop, no start. They put a fuel pump in it and still couldn't get it to start.. So I took a look , bad central junction block.  Now if they had done some basic simple checks they would of seen they had no power going to the fuel pump. 
Edited by skm
  • Like 1
  • Haha 1
Link to comment
Share on other sites

You made me smile reading your article. Here is my 0.02 cent story:

2005 Mercedes Benz E500 comes in from the local MB dealer, the complaint is that it has all kinds of intermittent electrical problems, it has new batteries, alternator, gateway and other modules, etc. On the preliminary inspection I find two ground straps broken, fix that and I hook up the picoscope to look at my current flow, see odd ripple, take a look at the serpentine tensioner and it's worn out with a new pulley installed. Changed it, car runs like a dream. Customer: "Are you sure that was it?! We spend over five grand in parts trying to fix it."

  • Like 1
  • Haha 1
Link to comment
Share on other sites

  • Have you checked out Joe's Latest Blog?

    • By Joe Marconi in Joe's Blog
      Typically, when productivity suffers, the shop owner or manager directs their attention to the technicians. Are they doing all they can do to maintain high billable hours? Are they as efficient as they can be?  Is there time being wasted throughout the technician’s day? 
      All these reasons factor into production problems, but before we point fingers at the technicians, let’s consider a few other factors.
      Are estimates being written properly? Are labor testing and inspections being billed out correctly? Are you charging enough for testing and inspecting, especially for highly specialized electrical, on-board computer issues, and other complex drivability work?  Is there a clear workflow process everyone follows that details every step from the write-up to vehicle delivery? Do you track comebacks, and is that affecting production?  Is the shop layout not conducive to high production? For example, is it unorganized, where shop tools, technical information, and equipment are not easily accessible to every technician?  Are you charging the correct labor rate and allowing for variables such as rust, vehicle age, and the fact that most labor guides are wrong? Also, is there effective communication between the tech and the service advisor to ensure that extra labor time is accounted for and billed to the customer? These are a few of the top reasons for low productivity problems. There are others, but the main point is to look at the entire operation. Productivity is a team effort.  Blaming the techs or other staff members does not get to the root cause in most cases.
      Maintaining adequate production levels is the responsibility of management to create the processes that will lead to high production while holding everyone accountable. 
  • Similar Topics

    • By ASOG Podcast
      Watch THIS Before Trying To Open A Business
    • By carmcapriotto
      On Record with Lauren Fix as she discusses the used car market and the importance of car maintenance.
      Lauren Fix, Car Coach Reports,  Total Car Score Podcast, is an automotive expert and analyst based in Buffalo, NY. She has written three books on automobiles. She has appeared on CNN, Fox News, Newsmax TV, CNBC, and USA Radio’s Daybreak USA show. Lauren's previous episodes HERE
      Show Notes:  
      Car Coach Reports Prior to covid selling cars: 17.5 million vs 13.7 million now. Average car profit to manufacturer: 10K...4 million sales lost People are buying out their car lease now Dealerships have 30% retention for car repair Repossessions are increasing- people bought cars during COVID, inflation and recession “Doing maintenance now will save you money down the road” Which cars can last 300K miles? Iseecars.com  “Never invest more in a car than it’s worth” USAmotorjobs  
      Connect with the Podcast:
      Aftermarket Radio Network
      Subscribe on YouTube
      Visit us on the Web
      Follow on Facebook
      Become an Insider
      Buy me a coffee
      Important Books
      Check out today's partner:
      Dorman gives people greater freedom to fix vehicles by constantly developing new repair solutions that put owners and technicians first. Take the Dorman Virtual Tour at www.DormanProducts.com/Tour

      Click to go to the Podcast on Remarkable Results Radio
    • By carmcapriotto
      With over 20 years in the hospitality industry, author and trainer Steve DiGioia shares some real world tips and tactics to improve your customer service, increase employee morale and provide the experience your customers desire. Steve has a detailed 57 individual steps for dinner service, what are your steps for customer service? Steve Digioia, Author and Trainer Show Notes
      How do I make you feel while I am providing this service? What can you do during the service part of the transaction to hook this customer in, hopefully for life? It has to be something more than just a mechanical aspect of it. There has to be something else that separates you from your competition more so than just the physical service you were providing, it's how I make you feel. It's how I make you feel appreciated. It's how I welcome you when you walk into my place of business. Many mechanics, they're focused so much on fixing that they don't realize that the waiting area has to be not only comfortable, and obviously clean, but it should be bright and welcoming. Use customer’s name 3 times. In a perfect world, you shouldn't receive less service because you are paying less. Versus getting extra service taken care of because you happen to be paying more, meaning, a higher-valued car.  If you want a consistent product, consistent service, a consistent experience, you have to have something like that because at a bare minimum, it reinforces the steps that the business believes is important to them to be able to service the client Standardized thank you note in every car
      Connect with the Podcast: Aftermarket Radio Network Subscribe on YouTube Visit us on the Web Follow on Facebook Become an Insider Buy me a coffee Important Books Check out today's partner: Learn more about NAPA AutoCare and the benefits of being part of the NAPA family by visiting www.NAPAAutoCare.com
      Click to go to the Podcast on Remarkable Results Radio
    • By TTP

      Premium Member Content 

      This content is hidden to guests, one of the benefits of a paid membership. Please login or register to view this content.

    • By carmcapriotto
      Live from the 2022 Transformer's Summit, keynote speaker John Dijulius categorizes the automotive industry as a 'grudge buy' for customers when they are at their most vulnerable. How is this an opportunity for your business to be the 'hero?' How do you make price irrelevant? John Dijulius, John Robert’s Spa, The DiJulius Group. John's had the privilege of working with world class companies like the Ritz-Carlton, Lexus, Starbucks, Nordstrom, Nestle, Marriott Hotel, Pricewaterhouse Coopers, Cheesecake Factory, Bausch & Lomb, Progressive Insurance, Harley Davidson, State Farm, Chick-fil-A, Entrepreneurs Organization, YPO, Aveda, and many more. Listen to John's previous episodes HERE Show Notes
      Drove for UPS- his wife was a hairdresser, and they opened a salon. John started getting involved in the business. “We aren’t going to be the best salon, we will be the best experience of your day.” Chambers of commerce businesses started asking John for business consulting.  20 years ago John’s first book came out and took him to the next level Business and Artistry Pengeleum   Making price irrelevant- based on the experience your brand consistently delivers, your customers shouldn't have an idea what your competitors charge because they aren’t window shoppers. Who is more expensive? Why are they?  “We do $10 haircuts” vs “We fix $10 haircuts.” Give the experience before you charge for it and justify it -“What does a $1,000 haircut look like? What is that greeting like? How is the massage during shampoo? What does a $1,000,000 keynote speech look and sound like?”  Grudge buy and losing time- automotive repairs. When you can come to the rescue when a customer is at their most vulnerable, there is an emotional connection and memory made. Customers asking about price- opportunity The biggest cause of anxiety is uncertainty- no update update for customers   Level 1 through 10 hairdressers based on expertise  “Discounting is the tax you pay for being average.” Things that make a brand something customers can’t live without- the quality of work, consistency, employee evangelism (educate vs sell), how do you make me feel, Capitalize the ‘C’ in Customer to show the emphasis in your policies and procedures  Building relationships with FORD- family, occupation, recreation, dreams Disney- know your role and be ‘on’ when you’re on, leave your problems at the door The Customer Service Revolution: Overthrow Conventional Business, Inspire Employees, and Change the World- John Djulius The Relationship Economy: Building Stronger Customer Connections in the Digital Age - John Dijulius
      Connect with the Podcast: Aftermarket Radio Network Subscribe on YouTube Visit us on the Web Follow on Facebook Become an Insider Buy me a coffee Important Books Check out today's partner: Learn more about NAPA AutoCare and the benefits of being part of the NAPA family by visiting www.NAPAAutoCare.com
      Click to go to the Podcast on Remarkable Results Radio

  • By nptrb, in Automotive Industry,

    By nptrb, in Automotive Industry,

  • Our Sponsors

  • Create New...