This post was written by James Avery and posted in the iATN

If you want a little insight into what diagnostics look like on the newest cars this is a great example. I'll comment on this at the end.

A 2014 Corvette with 1500 miles came in with a complaint of
intermittently the radio and/or Nav system would shut off at
times for 2 or 3 minutes and then come back on by itself and
operate normally. Scanning the infotainment system, U0028
was set as history in the radio. This signifies a MOST ring
break in the past.

Looking at MOST operation, the MOST network is a two wire
twisted pair infotainment data bus that runs 100 times
faster than high speed GMLAN. It is a unidirectional ring
network that has a master module that serves as a MOST to
LSGMLAN gateway. There are other satellite modules in the
MOST ring. Requests are usually supplied by other non MOST
modules connected by a LIN network, The request is sent by
LIN to the MOST module which sends it along the ring network
and watches for a return. Each MOST module watches the
module before it in the network for data. This occurs in an
downstream position only as the ring is unidirectional. The
modules are assigned places in the MOST ring by the master
module and assigned a numerical position ID number.

Still with me? If a module loses data from the module
upstream of it in the ring, this is known as a ring break.
At this point, the module first losing data will declare
itself on the ring as the Surrogate MOST Master Module. This
happens ONLY while the ring break is active. Surrogacy is
cancelled if the communication is restored. When the ring is
broken, only modules downstream of the break will send
information to the radio which usually is the MOST master
module. Ring architecture can be viewed on GDS2 as the Last
Working MOST ID of Node XX. XX will be the assigned ID
number of the module. The numbers will increase from node 1,
(usually the radio) through the other nodes in a downstream
direction.

On this vehicle the node IDs are as follows....

Node 1 - radio

Node 2 - Audio Amplifier

Node 3 - Human Machine Interface Control Module

Node 4 - Instrument Cluster

The Surrogate MOST Master Upstream Position value on the GDS
display was NONE as the ring break was not evident at the
time that I looked at the vehicle. How do we diagnose it? I
had two options. One would be to check the entire MOST
network ring for module/connection problems. The other would
be to test at the time of failure when the ring break
reoccurs which would supply me with information about the
declared Surrogate MOST Master module. I drove the vehicle
with a laptop, monitoring data. After 12 miles, the radio
shut down. Looking at the radio data stream I saw Surrogate
MOST Master Node Upstream Position value was 2. I drove back
to the shop and the radio started working again after a mile
or so.

Now I know the module that declared itself as the Surrogate.
The Surrogate MOST Master Node Upstream Position value again
reads NONE as the problem is not occurring again and
Surrogacy is no longer enabled. Although the MOST ring
information is transmitted downstream, we need to look
upstream for a diagnosis. The upstream position set was
position 2 so we need to count backwards on the ring from
the master module to find the position, not the assigned ID.
The last MOST module on the ring is the Instrument Cluster
ID 4. This will be in position 1 counting upstream. The next
module is the HMI module, ID 3. This will be upstream
position 2. Therefore the HMI module was the module that
established Surrogacy during the ring break. Still with me?
The HMI module is not a failure point and is operating
correctly. It just lost communication with the module
upstream of it in the MOST ring that was transmitting
downstream to the HMI module. So, the ring break must have
occurred BETWEEN the next upstream module which is the Audio
Amplifier, ID 2 and the HMI module, ID 3 in the MOST ring.

Checking the wiring pin fits at the HMI module inputs, I was
able to re-introduce the ring break by wiggling the wires
and found a loose pin fit at one of the connectors. A new
terminal fixed the problem.

------------------------------------------------------

• I wonder how aware most managers are of the fact that in order for top techs to deal with today's cars we cannot rely on just the training that is typically provided. Many of us write up repair events such as what you just read through sometimes as a straight essay, and quite often just short of revealing what the failure was and letting the other techs practice looking up the information and figuring out the problem the best that they can without actually touching the car. We will do things like ask for a measurement at a particular pin connection with a scope/voltmeter and of course even send snapshots of serial data back and forth.
  
  Maybe you knew, maybe you didn't but most of us have been very active at doing this for the last fifteen to eighteen years. BTW James has another one out that he wrote after this one and both of them demonstrate that the cars can only test themselves so much, and the tools we have otherwise cannot diagnose the cars. It takes techs, dedicated, skilled, and committed way beyond what the compensation for the effort returns. The ugly truth about flat rate is for now that Corvette paid James straight time. If I was I the stall next to him while he was fixing this and doing customer pay front end and suspension work, I would have generated three to four times the income that he got paid.
  
  Now how does that make any sense?
  
  We always hear the advice of work smarter not harder. That simple line essentially suggests there is no reason to attempt to learn how to solve that Corvette's problem and is the heart of why it is difficult to find qualified technicians today. The need for speed and the one sided evaluations of the techs from the flat rate perspective has worked to discourage us from making the kind of investment in ourselves that we could grow into being the kind of technician that James is. What's even worse is many of the comments and especially the political pressures in the bays serves to duly punish anyone who genuinely tries. I hope you really hate seeing it written that way, in so much as to not just try and shout it down but to look closer at what really has been going on in all of the shops, and start managing to correct it. Straight time for that diagnosis and repair, what a joke. Soon the Corvette will go off of the straight time and that would probably be assigned the .3 like all of the other GM diagnostic routines that actually still pay anything. Of course the tech could beg for additional time which may or may not be granted. 

Customer reports the starter cranks slowly at times

Here is a capture of the system voltage and the battery current with a high amps probe.

Based on this capture what is wrong with the car?

This is a capture of a bad starter where the brushes are not staying in contact with the armeture.

#starter, #Honda, #high, #amps, #probe

Engine Rebuider Magazine Article

Here is an article that deserves some feedback.

http://www.enginebuildermag.com/2013/12/time-in-a-bottle-reasons-behind-changing-engine-oils/?utm_source=EB+Newsletter+-+Subscribers&utm_campaign=25d0280803-enginebuilder+newsletter&utm_medium=email&utm_term=0_6ca466f60c-25d0280803-83615821

Over the last four to five years there has been a lot of effort put into helping techs learn about and understand the changes in the engines and emissions systems in todays cars, and the oils that are engineered to protect them. Prior to that this article would have come and gone and just about all of us would have not thought twice about it. But thanks to efforts and information shared by Kevin McCartney via training classes and in the iATN top techs know that this article is very short on the facts today. ILSAC was formed by the oil companies to try and please the manufacturers. It has always been an extension of the API. The article failed to mention ACEA which is controlled by the manufacturers.
The author spent a few moments mentioning GM's dexos1 specification. What the readers need to know is that if it really isn't getting traction in sections of the market that is a reflection on the lack of training that has been taking place on this subject. That is a real trade problem and what makes that worse is this article is working towards placating that group into thinking they are still doing right by their customers, in short they are not.
Catalyst and O2 sensor degradation from additives is not only well documented there is a reason why a lot of the O.E's  put cores on replacement catalysts today. Its not so that they get to recover the materials in them. They are doing it to measure the contaminants and from there can literally prove if the vehicle owner was having the car serviced correctly or not. It has been suggested that contamination of a catalyst may become grounds to deny an emissions warranty replacement if this kind of damage is proven. 
In the end the authors perspective appears to still be rooted in the technology and understanding of the 60's-80's that most of us had. He like many of us has failed to keep pace with the changes that have occurred and needs to get back into a classroom and then re-write this article.

Getting yelped

Our little shop took years to build, and yet at the same time we still aren’t done trying to build it. Operated by my wife Beth at the front desk and myself as the only technician we have taken the path less traveled when it comes to operating an automotive repair shop. Today people from all over the county and even other shops rely on us to solve the toughest problems that can occur on some of these cars. To be that shop, that tech, I have had to work harder than everyone else that I have ever been around both on the job and at home studying when I should have been off the job. That’s an extension of a habit that started in the late 70’s when I was a young technician and was struggling to learn how to be a good mechanic. When someone would say something like “You’ll never be any good” I took the anger and hurt that I felt and used it to push myself to study so that I would be the best technician that I could be and hopefully someday show them that they were wrong. I must say there have been many times that I wish that I would have simply walked from this career away instead of constantly striving to improve myself and my capabilities. Early in the eighties I started studying electronics because of how poor the wages and working conditions were and the plan then was that I was going to quit fixing cars and go make a living working on computers. Little did I know how that education would make me better at dealing with the computerized cars way back then as well as today and that is part of what makes our little shop different.

Have you ever taken your car into a shop for one thing and come out with a list of recommendations that cost hundreds if not a thousand or more dollars?

We don’t up sell maintenance services to try and generate easy dollars like so many places do, I’ve never believed in that approach. Back when that first started the business guru’s were running around telling shop owners “You can’t make money fixing cars, sell services”. They would point out that it took a much more experienced technician (who of course cost more to employ) to fix cars while there were fewer things to go wrong and greater profits if the shop simply concentrated on just doing the easiest work. I had been a technician for about ten years when this was all going down and had been gaining some recognition for my efforts and here were “experts” telling shop owners they shouldn’t be employing guys like me who could take on anything, they only needed entry level people to install tires, batteries, brakes, and to flush fluids.   

It was strange how it turned from I could never be good enough as a mechanic to being too good to allow a shop to be profitable in such a short time but that’s a mechanics life in a nutshell. It seems no matter where a tech is in his/her career there is always someone going out of their way to cut them down, and now I find this little gem of a review in Yelp. “One of the worst experiences I have ever had, the man is very confrontational and insulting. His character and workmanship is very very poor.” Adam W.

Well Adam I’d like to address this with you, but I can’t because there is no Adam W in our customer list. At the same time I’m afraid that I might live up to being confrontational at this point because working  90-100 weeks for the last thirty eight years has me pretty worn out and there just isn’t enough left in the tank to try and stand back up again when someone is trying to knock me down.  The facts are, our regular customer’s opinions of us and our shop don’t match yours. Plus the fact that we are the hero’s to thousands of people who were sent by their regular shop for us to solve a nightmare issue who routinely re-recommend us when someone else is dealing with a tough diagnostic problem.

The interesting part is we don’t actually make a good living dealing with these kinds of problems. The cost of the O.E. scan tools that we have been buying for the last fourteen years, while our competition hasn’t been making a similar investment has been crippling for us. The continued training expense reached a point that it turned into a way to supplement the shops tooling expenses when I started working a second career as a continuing educational instructor.  (That’s how I’ve been hitting the 100/hr weeks of late) Many of the problems that we solve on these nightmare cars take significantly more time to figure out and repair then we can bill for and keep the customers immediate interests in mind. In a lot of ways we prove that the guru’s were right, you can’t make money fixing these cars but that is what our shop is all about and since our customers need us we push onwards, in spite of our own personal challenges.

During the last eight years Beth’s epilepsy got so bad that surgery became the only chance for her to get any relief. Last year they took out the entire right temporal lobe of her brain to try and stop the clusters of seizures that she was experiencing.  Thank-fully that has stopped the periods where she could take twenty to thirty seizures in a cluster every three weeks, but didn’t completely eliminate them. The doctors are now starting to evaluate and try to decide just what to do next. For the moment they are working with the medications and we know not to expect a perfect result but any brief period that see’s her free from events is a blessing.

Three weeks before her surgery we took the only one week vacation we ever had since we got married thirty four years ago, previously we had only one four day vacation back in ’95. We don’t live beyond our means and that’s all we have ever gotten to have. We only took that one before her surgery because we didn’t know what we were going to have after it.

So now you all know a little more about us, and if you want a shop that takes pride at going straight in at a vehicle problem, solves it, and gets straight back out without trying to sell you everything under the sun, then we are who you are looking for. As a three time NAPA ASE tech of the year, an ASE Certified Master Technician since 1982, two time GM Master Technician, a member of the GM Master technician Advisory Council, a technical writer and Instructor, and I even host my own live call in radio show and a RepairPal Certified shop we are doing everything we can possibly do to be ready when you need us. We are far from perfect and sill not afraid to work harder than the guy down the street all while walking  the road less traveled.

Fuse 41 Ford Ranger

A 2001 Ford Ranger was blowing fuse 41 if the vehicle moved at all. A local transmission shop had the truck because when the fuse blew it caused a loss of power to the transmission solenoid pack. When they didn’t find the problem they sent it onto us for diagnostics. When a fuse blows as soon as you plug a new one in, the routine a technician should use is to substitute a load in its place in order to power up the circuit. A headlight works very well for this.  By connecting the headlight in place of the fuse “the short” simply completes the ground circuit that is created and the headlight lights up. Then to do the diagnostics all the tech has to do is follow the current flowing in the circuit to the problem by measuring the current that is flowing and then follow the wiring harness using a low amps current probe. That’s a high tech way to make easy work of what used to be a difficult problem.

With this Ranger the fuse didn’t blow immediately most of the time, but it could blow so quickly sometimes that the truck didn’t even pull out from starting it up. That meant a different approach needed to be taken for this problem. By installing a circuit breaker via a jumper harness the current probe could be connected to the jumper harness and the current that was flowing in the circuit could be monitored. This first capture was the current that was flowing in the circuit when the connections were made and the spike occurred as the technician was getting into the truck to try and take it for a road test.

 

Here is a low amps probe connected to the circuit with jumper wires and a circuit breaker in place of the fuse.

 

 

 

 

 

For a diagnostic tech, that’s a great result for the first test. Just disturbing the body of the vehicle generated a current spike, that’s a classic example of an abraded wiring harness that is grounding somewhere. Now it’s just a matter of finding the location of the harness failure.

 

 

 

Fuse 41 feeds the transmission solenoids as mentioned previously, it also feeds all of the O2 sensor heater circuits and the canister vent solenoid. Most of the circuit is visible without too much effort, the only part that isn’t easy to see is the part of the harness that is inside the transmission. The goal now would be to prove if the problem is inside or outside of transmission portion of harness if possible. If a visual inspection of the harness doesn’t reveal the cause of the problem, then if necessary the plan will be to use a second current probe on just the transmission harness.  That way the next time a current spike occurs, if both current probes show the spike then the problem would be confirmed to be inside the transmission.

Inspecting the harness and the O2 sensor connections didn’t reveal any problems, but when the vent solenoid portion of the harness was checked the harness was clearly abraded and intermittently contacting the bed of the truck.  The repair required the replacement of the pig tail connector for the vent solenoid and by creating some relief for the assembly the wire could be assured to not abrade again in the future.  While this event was very easy and straight forward, by taking a disciplined approach it wouldn’t have mattered if this would have been a more complicated problem. The solution would have been achieved in an efficient manor and that’s the key when it comes to doing diagnostics. A solid diagnostic routine is one that is repeatable and doesn’t fall for the inherent traps that are based on relying on silver bullets. Fuse 41 has been known to fail because of a bad heater circuit inside of any one of the O2 sensors. It’s been known to fail because of problems with the solenoid pack or its harness inside the transmission. There can also be main harness issues as well as the problem this time of the vent solenoid portion of the circuit like this truck, but none of that matters if a tech can come up with his/her own game plan and again be able to take a disciplined approach, he/she will go straight at the problem and that's exactly what the customer needs them to be able to do.

The Colorado Final, and a Shout to Jim Garrido for the strategy that was used to diagnose it.

The owner took a nice ride up to Erie Pa and did some shopping at the wineries for the holidays. That gave him the trip that he needed to run the fuel out of the truck, and have some real time for the cleaner to do its job. Over the weekend he had a couple more shorter trips and by Monday when he stopped by the shop the smile on his face was promising. He reported that he could clearly feel a difference in the truck, he was certain that its performance was notably improved.  

The thing to do now was to collect some data with the very same checks that were done initially. What was found was at idle the long term trim was 24% and the short term was 19 for a total of 43%. That’s better but only marginally. At 2500rpm no load it was 19% long term and 12% short term. That was clearly better at 31% total trim but still not in control. At 1500rpm in gear against the brakes it was also much improved and in the total range of 30%. Its important to note that the same two monitors were still not complete, the evaporative and the catalyst. With our sudden cold snap, the evaporative monitor not completing was no surprise since a number of the code enable criteria have minimum ambient temperature requirements in the 40f range. The catalyst monitor didn’t run because the fuel trims were still too lean to allow that to take place at idle.  While the fact that the fresh fuel and the cleaner made a difference was promising, there was still a pretty good chance that the truck might need new injectors. The owner planned to return in two days so we could check one last time.

On Wednesday afternoon he returned only this time he reported that the light was back on. However it was running even better than it was on Monday. So what do you do with the light being back on? The right thing to do is approach it exactly as any other repair visit, and that means forget everything you already know while you are doing the diagnostics. With that plan in mind here is what was found with the truck.

The code was a P0171 again, lean air/fuel ratio. The freeze frame showed that it had set at idle. Starting the truck up the total fuel trims were 40%, with the long term being 25% of that. Speeding the engine up to 2500rpm the total fuel trim dropped to 20%, with the long term at 19% and the short term at 1%, that’s a big difference from the previous data! Loading it up against the brakes at 1500 rpm the total trim was below 10% with the long term at 7% and the short term varying around 2%. That’s good enough, not perfect, but good enough. So why was it so lean at idle still, and what would you do at this point?

False air, or a vacuum leak are quite probable now because they will have a big impact with low engine speed and low cylinder charge demand. Under faster engine speeds there isn’t as much time to impact the air fuel ratio, under load against the brakes there is little to no manifold vacuum so a vacuum leak can’t impact the air fuel ratio much at all. That means its time to get the smoke machine out and check for a leak. With the mass airflow sensor at the air cleaner, wrapping the air filter with plastic wrap will allow all of the intake system to be checked. A few moments later smoke was seen pouring out from under the resonance chamber that is in-between the MAF and the throttle body. Pulling it off the breather hose wasn’t connected to the valve cover, and the oil staining in the area suggested that it had been off of there for some time.

Once it was secured back in place, the plastic wrap removed from the air filter and re-installed,  the fuel trims were reset with the scan tool and it was time to re-evaluate the fuel trims. By resetting the fuel trim, the short term trim alone had to make all of the correction, at idle that was now 8%, 2500 rpm no load 5% and against the brakes 5%. The truck was fixed but we weren’t quite done yet, he still needed his emissions test.  In Pa he passes with one monitor incomplete, and in this case that was going to be the evaporative monitor because of the ambient temperature as well as needing to have a cold soak where the coolant and intake air temperatures had to drop within the code enable criteria range.

The customer was provided specific instructions for how to drive a cycle and about twenty minutes later he returned with enough monitors completed to allow the emissions test to run and his sticker finally issued.

This truck and how it was diagnosed and repaired is based on training case studies written into CTI classes by Jim Garrido.  The best way to thank him for sharing this kind of information is to attend some of his classes ASAP.

2005 Colorado Too Lean, continued

At this point the truck is confirmed to be running too lean, but why is it too lean? This could be a fuel quality issue, fuel pressure problem, injector problem or it could be a base calculation error. The more that can be ruled out with scan data, the less physical testing that needs to be done to prove what is wrong.  Some of the things to think about are what information the PCM uses to make its base fuel calculation. GM uses a mass airflow sensor (MAF), and the software takes that MAF value and calculates the engine load and from there what the injector pulse width should be under those conditions to provide the engine with the right amount of fuel.  While on a road test the accuracy of the MAF can be checked by watching that engine load calculation in scan data. During a wide open throttle acceleration a snapshot of the engine data can be captured and then later played back so that the engine load pid can be examined to see if the MAF sensor reported.

During the road test it was easy to get the MAF to report 100% engine load.  So the PCM should have been calculating the correct base pulse width and turning the injectors on long enough for the engine to get the right amount of fuel. However it was still very lean under all phases of operation and the fuel trims were adding 40-45% to the injector pulse width. One note-able observation was that during a hard acceleration where the PCM commands an open loop enrichment to provide full power, all four O2 sensors reported over .88 volts, and then on a closed throttle deceleration they all fell to 0volts showing good amplitude and reaction. At this point it’s back to the shop for the last phase of testing.

Once back in the shop the fuel pressure was confirmed to be at 63 psi, with enough fuel pressure and fuel volume that mean the only two things left that could be causing the problem were fuel composition/quality or restricted injectors. With the vehicle otherwise operating reasonably well there was an option on how to proceed and its one that the customer chose to try. Instead of doing specific fuel quality testing and manually cleaning the injectors, he was to go fill up at a Top Tier fuel station, and add a very specific fuel injector cleaner, Chevron Techron to the tank.  His travel plans included one immediate trip of about 250 miles to start the injector cleaning process and run all of the old fuel out of the tank. Then we would check the fuel trims and see if anything changed after he refilled the tank.

To be continued…