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There's no argument that even the simplest vehicle's coming off of the assembly line today are equipped with a technology stack that very few of us ever imagined. Today, the average age of the vehicle on the road is currently running at 11-12 years. From my perspective, this is the beginning of the exponential growth in vehicle sophistication. Some of us are currently prepared to competently analyze, service and repair these vehicles however; a great percentage of the industry is not. On top of that, vehicle service requirements have been changing as well, which presents additional challenges moving forward.
How does the industry stay educated? One might consider looking to many of the corporate partners who support iATN's mission. Many of them offer excellent levels of training and continuous education.
iATN is now in it's 22nd year and since its founding and in that time we've witnessed the evolution of OBD2, alternative propulsion systems and other technologies leading this revolution. Many of the articles found in this issue of the iATN Review reflect much of the new technology that most in the aftermarket have yet to see. We hope that you enjoy this issue and continue to keep on learning and supporting the mission and goals that iATN was founded upon.
Scott Brown
iATN President
G.M. MOST Bus Diagnosis Made Easy
Technical Discussion Forum
James from Florida
A 2015 Silverado came in today. The complaint was MyLink display is dark. With the engine running, this was the display.
[2015 Chevrolet Silverado 1500 LS, Photo]
The display was not illuminated, the radio would not play and all the control buttons were non-functional. What's first? Check powers and grounds? Not really as we have a multiple failure. The display is controlled by the HMI module but the radio is also not functioning.
Checking for codes set, I found U0028 set in the radio as current and U0029 set in the HMI module as current. OK, let's look at radio MOST data next.
[2015 Chevrolet Silverado 1500 LT, Scan Data]
Note that a SURROGATE MOST MASTER NODE UPSTREAM POSITION of 2 has been set but at the same time, the NUMBER OF MOST COMMUNICATION BREAKS is set at zero. Why?
The answer is in the codes set. U0028 tells us that a MOST communication error is occurring. It can be a ring break, short to power or ground or a data line or a internal module fault. A lot of possibilities but U0029 refines it. U0029 tells that a communication error is occurring but the MOST ring still has integrity. Because of this, the number of communication breaks is zero and no module has declared itself as the SURROGATE MOST MASTER MODULE.
How to find the problem? The MOST ring is unidirectional and has only 4 nodes on this vehicle. As seen in the data, node 1 is the RADIO, node 2 is the CD, node 3 is the HMI module, and node 4 is the IPC. Since the SURROGATE MOST MASTER NODE UPSTREAM POSITION is 2, we need to count backwards in the MOST network for this position. The first position backwards is the node 4, IPC. The second is node 3, HMI module. So our communication failure is occurring before node 3 in the regular orientation which would be node 2, CD player.
Since U0029 is set I don't suspect a wiring and/or connection problem. The next step is to see if I can communicate with all 4 nodes. I could not establish communication with the CD player, but the other 3 nodes were normal. I removed the CD player and jumped the connector data lines. The MyLink display lit up and the radio started playing and all the controls functioned normally now. The failure was due to an internal module failure in the CD player.
G.M. MOST really isn't that tricky if you collect data first and analyze the failure before you jump into component testing.
Elementary Communication Diagnosis
Technical Discussion Forum
James from Florida
I've posted many LAN diagnostics on iATN over the years. Since I specialize in LAN and electrical diagnostics, I do a lot of them. It's not uncommon for me to work on 2 or 3 a day. As few techs want to work on them, most are shuttled to me. I don't really mind as I've done so many of them that it has become very easy to me.
Because of this, most of the ones that I post are uncommonly difficult or unusual. I've been receiving e-mails from some members that are still cutting their diagnostic teeth on LAN diagnosis and who want to see some of the more elementary diagnostics. You need to walk before you can run, right? So, this post is a common, fairly easy LAN diagnosis for all the lurking newbies out there.
This 2011 Equinox came in today with a complaint of intermittently shutting down and not starting. The customer says that he drives down the road and all the dash warning lights come on and the engine shuts down. Then, it will not crank until he sits for and hour or so, then the cycle begins again.
The vehicle started normally and drove in the shop normally and I parked it and shut it off while I finished another car. An hour later, when I went to start it, all the dash lamps illuminated normally but the vehicle would not crank....no click, nothing. From the owner's description, I anticipated a module or LAN problem. Now that it won't start, the diagnosis becomes much easier than chasing an intermittent failure.
I did'nt even check codes first. I just looked at the HSLAN voltages.
[2011 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
It's pretty obvious that we have a problem. look at how high terminal 6 voltage is. Just to make sure, I looked at the LSLAN next.
[2011 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
Completly normal. How about the Chassis Expansion bus?
[2011 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
Normal also. Good, we can concentrate on the high Speed LAN. Let's see who's present on the LAN.
[2011 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
OK We're missing the ECM and the TCM. It also says CAN BUS open. The ECM is the last module on one side of the LAN and holds the terminating resistor. The module before it is the TCM. Before the TCM is the PSCM. Since we can communicate with the PSCM but not the TCM and ECM, our problem must be before the TCM, right? It could be caused by a module or a wiring problem. My first place to check is the connectors and pin fits at the PSCM and TCM.
The TCM is easier to get to so I unplugged it first and checked the LAN connectors between the PSCM and the TCM for pin fits and corrosion. All seemed OK. Next, to access the PSCM, we need to raise the vehicle and unplug the connector from the top of the steering rack. This connector is difficult to release as the tab is above the connector and hard to depress. I saw that part of the connector was broken off. I guess somebody replaced the rack before and just gomered the connector off. The wire standoff was unhooked also. After removing the connector I pulled gently on the wiring and the LAN wiring from terminal 6 stretched out like a rubber band. It was obviously mostly broken inside the insulation., A new connector spliced in restored our communication for a fast, easy fix. Of course, if the problem wasn't easily evident, I would have needed to do some voltage and resistance testing but not needed in this case.
2013 Volt Cell Section 3 Replacement
Technical Discussion Forum
James from Florida
The Volts have been around long enough that we have seen several needing cell section replacements due to service life concerns. This vehicle has 123,000 miles on it and has been setting service messages and codes. I diagnosed cell section 3 as needing replacement. Here's a look at the necessary procedures.
The Gen 1 Volt has 288 L.I. cells laser welded in groups of 3 to form 96 cell groups. Battery section 1 has 30 cell groups. Section 2 has 24 groups and section 3 has 42 cell groups. They are set up in a T fashion and cell section 3 is the transverse section. The BECM and 4 interface control modules are attached to the top of the cell sections.
First, we need to remove the HV battery.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
Next, the cover is removed.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
Cell section 3 is the sideways mounted section. Here's the new assembly ready to install.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
First, the HV bus bars, battery hold downs, manual disconnect housing, coolant tubes, wiring harness and the interface control modules need to be removed.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
This cell section is very heavy and unwieldy so a holding fixture is used to remove and install the cell section. Note that the entire HV battery assembly is live under the cover and proper precautions must be followed as fatal voltage is present at all times.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
A chain fall is used to remove and replace the cell section.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
After reassembly, before the cover is installed, the new cell section must be balanced to match the existing other two sections. A special tool must be used along with cables, fuse block and interfaces. The balancing procedure takes 2 to 4 hours and the cover is then installed. There are also adapters to test for coolant leakage as well as adapters to smoke test the battery housing and cover for leakage.
[2013 Chevrolet Volt, Engine/Propulsion Photo]
Using Code Set Order to Diagnose
Technical Discussion Forum
James from Florida
I just repaired a 2010 Equinox with a complaint of ABS light on and Service Stabilitrack message displayed. The vehicle started and ran normally driving into the shop and the light and the message were displayed as in the complaint. My first test was to check for codes set. I did a vehicle code check of all modules and saw only these codes set in the EBCM.
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
The problem seems to be limited to the HS Chassis Expansion Bus, although the EBCM is also on the main HS bus. That calls for a fast look at the main HS bus first.
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
The voltages are normal. Let's see if the EBCM is present on this bus...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
OK, it's present on the HS bus, how about the expansion bus?
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
Well, no modules are detected and the bus is shown as CAN Bus open. Let's see if it is...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
It sure looks like it is either open or shorted to ground. With key off, I checked the expansion bus resistance and saw 61.2 ohms and normal resistance to ground on CAN A and B. So, it's neither open or shorted to ground with key off but low voltage with key on. Why? There are other possibilities. With key on, engine off, I cleared codes and noted that the codes did not reset immediately. Monitoring the codes set, this was the first...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
After 20 seconds more, this was set...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
And 30 seconds later...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
Time to analyze data collected. The first code set was by the PSCM for invalid data from the SAS. Since the PSCM is not on the expansion bus, this data must be transferred between buses by the EBCM. Next codes set were from the EBCM showing Can Bus B off and a loss of communication with the MAASM. And the third code set was from the EBCM losing communication with the SAS. What does all this mean?
The first problem detected was invalid data from the SAS. If the EBCM sees invalid data from either the SAS or the MAASM, it can shut down the CAN Bus and substitute values for these modules. Once the Bus is open, the other two modules cannot communicate with the EBCM and codes were set for loss of communication. What's the best way to prove this theory as we cannot read any data on this bus to help us. I unplugged the SAS and jumpered the 4 com lines and rechecked the expansion bus voltages, seeing this...
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
OK, we now have an active expansion bus again. I installed a new SAS and rechecked the bus for modules present.
[2010 Chevrolet Equinox LT, ECM/Inputs/Outputs Scan Data]
Everybody is present and talking together now and the lights and messages are gone. A little thought analyzing the failure can go a long way.
CKP Code, but CMP was the Fix
Technical Discussion Forum
Geoff from Hawaii
This is basically a case study to add information regarding the "inverted waveform" phenomenon that we can encounter.
So the shop owner got a 2005 Nissan Titan, 5.6 L (VQ56DE ?) at auction. It was setting DTC P0355 "CKP sensor ckt". He had our helper r&r the CKP sensor. No fix. So, I get to look at it.
Like all good boys, with a DTC for a CKP (or CMP) sensor, I scoped both at the ECM. Blue is CKP, red is CMP. I got this;
[2005 Nissan Titan LE, ECM/Inputs/Outputs Waveform]
Comparing that to a known-good from the library, and the Nissan SI image in All-Data, the CMP is upside down. I know that has been discussed before. There are varying opinions on the subject. Some say that ECM's don't "see" waveforms like we do. Our eyes see lines with humps. Riding low and jumping high, or vice versa. An ECM sees "transitions", or "only sees a falling edge" or "rising edge" etc. Well since no one agrees...and the falling/rising edge theory shows this engine as being out-of-time...and the engine ran just fine...I replaced the CMP sensor.
Now the signal looks EXACTLY like it is supposed to;
[2005 Nissan Titan LE, ECM/Inputs/Outputs Waveform]
and the DTC for CKP does not set. Amazing!
Additional info;
1. I was using a G-Scan. For those not familiar with that great scan tool, the DTC screen is live, and you can clear a DTC from that screen. (no backing-up to a different menu). If I cleared the DTC KOEO, the DTC set as soon as I cranked the engine. If I cleared it while the engine was running, it came back instantly. 2. Curious if my theory that a "wrong" CMP signal could set a CKP DTC, I unplugged the CMP, however this resulted in a P0340 "CMP sensor ckt" and a crank-no-start condition. 3. In the DTC criteria for P0335 it mentions the CKP "...signal is not in the normal pattern..." but does not say anything about "relative to (something else)"... and of course the CKP was NOT irregular here, the CMP pattern was. 4. After all my reading on the subject, I was almost sure it was a bad ECM or stretched chain. (nope....LOL) hope this helps someone else someday.
aloha from Maui.
and a very special thanks to the donor of my PicoScope
Used Chrysler PCM Identification
Technical Discussion Forum
Michael from New Jersey
[Correct pcm, new and used.] [rebuilt pcm; semi programmed]
Sometimes my customers are required to use a used module on a Chrysler product. The original pcm calibration is 04727737AI. The semi programmed number of the new unprogrammed pcm was 05150247AC. Now the problem; 247AC can be programmed into 8 different calibrations.
The programming is a one way process; once programmed to one of the 8 calibrations, there is no return to either the universal status or another calibration. So when the recycler tells you that they are sending a 247AC; because it is the latest calibration; they are incorrect, unless the 737A? is labeled as such. Notice that the 737AI sticker is on top of the 247AC label, another hint. No, I do not know what the difference is between the 8 calibrations; I do know the wrong calibrations usually turns on different dashboard warning lights that can not be shut off.
The replacement rebuilt Chrysler unit will also need to be programmed to the correct calibration. But the Chrysler parts person may also state that the correct number for a used unit is 247AC. Incorrect; the calibration makes a huge difference.
When ordering a used pcm for Chrysler, the module P/N must match; except for the last letter. There are a few exceptions on very late numbers that are different, because there are only so many usable alphabet letters.
Corvette Ghost Misfire
Technical Tips Forum
James from Florida
A 2011 Corvette came in yesterday. It had been to another dealer, a Corvette specialty shop, and a general repair shop to repair a continuing SES complaint. The customer stated that the SES light came on every day with no driveability complaints. The other shops have already replaced the spark plugs and wires, the fuel injectors, fuel pump and crank and cam sensors without repairing the complaint.
The SES light was on when I drove the car in the shop. Scanning the control module system, I saw p0300 set as current in the PCM and no other codes set in any module. Looking at the history misfire counters, each was reading in the thousands without too much variance between cylinders. The car idled normally and no misfires were set yet the active counters kept increasing.
I cleared the counters and let the car idle in park for two minutes and recorded this.....
[2011 Chevrolet Corvette, ECM/Inputs/Outputs Scan Data]
During this test, the vehicle idled normally and no misfires were felt. I have always called this condition where misfire counters increment but no actual misfires occur as "ghost misfires." Next, I cleared all the counters again and put the car in drive and idled for 2 minutes and saw this...
[2011 Chevrolet Corvette, ECM/Inputs/Outputs Scan Data]
Any ideas? This is a seldom seen failure on Corvettes. Inside the torque tube where they cannot be seen without disassembly, front and rear phenolic type couplers are used on the actual driveshaft. These couplers can wear and develop play or actually start to come apart. In park or neutral when just the drive shaft and torque converter are spinning, back and forth movement can occur that the PCM sees with the crank sensor and can interpret as misfire on all cylinders. Putting the vehicle in drive or reverse loads the driveshaft and stops this motion and the ghost misfires cease. If you look at the misfire graph, you can almost see the cycling occurring.
If you remove the torque tube and tear it down, the couplers can be visualized. In this case, the vehicle had a GMPP extended warranty so the entire torque tube was replaced and after idling in park for 20 minutes showed no abnormal counters incrementing.
Something to remember in case you run into this scenario as many shops have their shorts handed to them when faced with this type of failure.
Stiff GM Magnasteer Rack & Pinions
Technical Tips Forum
Juan from California
This has been a torn on my side for a while now. Fought with several suppliers, rebuilders&etc. No one seems to have answers for me. Seems to affect 98+ Sevilles & 2000+ DeVilles.
Problems usually start after replacing the rack n pinion units off the shelf. A lot of the times, the old rack has broken brackets on the passenger's side, so the whole unit has to be exchanged. After that, the steering becomes incredibly stiff. You can go through many rack n pinions with the same stiff symptom!
After searching the manual, archives & internet, no luck on a solution! After changing out racks, power steering pumps, hoses, etc. No answers!
The service manual doesn't give you a lot of information on how magnasteer works, just that the steering gets lighter on low speeds & stiffer on higher speeds. There are codes for malfunctions, but no codes ever pop up on these cars.
All this time, I was assuming the power steering has a certain assist & the magnasteer system creates resistance at higher speeds, but apparently, it's the opposite! Magnasteer assists in low speeds! Don't believe me? Disconnect a properly working unit & you will see that the steering will get stiffer.
So why the stiff steering? It appears rebuilders treat 98+ Sevilles & 2000+ Deville racks as the same units! They look the same, feel the same, but have one very tiny difference. The 2 wires going to the magnasteer unit are backwards! If you switch the wires around, you will create a stiff rack in low speeds! Polarity is critical on the Magnasteer units!
Now, it makes sense. 90% of the Cadillacs out there are DeVilles. About 10% Sevilles, which is a rarer car. Most of the racks on the shelf are from DeVilles! So if you put one of those on a Seville the polarity on the Magnasteer is backwards, making it stiff! I've only had one DeVille so far where the steering was stiff after a rack n pinion replacement & I've had many Sevilles with this problem.
Now, I have an easy fix. Switch the wires on the connector around! Before this solution, I would have the same unit rebuilt & avoid off the shelf units, but that's not always possible.
Hope this helps some one.
One More ASE thought
Shop Management Forum
Nathan from Colorado
Just one more thought about ASE, testing times, testing locations.
According the the BLS, there were 740,000 automotive technicians/mechanics in 2014. So, there's probably 750,000 or so now.
According to ASE, there are 213,000 ASE certified technicians, only 74,304 who are Master automobile technicians.
So, 10% of the technicians in the US have achieved ASE master status. Less than 1/3 are ASE certified at all.
If more technicians were to become certified, even if we just made it up to a little over half, that would greatly increase the demand for ASE testing, provide ASE with more revenue and (I'm guessing here, but it's probably a good guess) result in more testing locations and times. I'm sure it costs quite a bit of money to put on those tests, and if they rent a room, they have to pay the same amount for that room if there is 5 people in it or 50.
So... my point is... there is only one group of people that can change the way ASE does things, and that is us, the professional technicians. Complaining about what ASE is or isn't won't really change anything, but if we get more and more technicians to become part of ASE, then change can occur. Otherwise, it's just griping.
I feel funny writing this post, because I've been one of those who has griped about ASE and their relevance quite a bit. I'm still not completely sold on their benefit to a shop owner, but I do believe they are the best that we have right now, and it's better to work with them and try to make things better than it is to just complain.
Just my .02 on a Monday morning while I'm waiting for my 8:00 am appointment to show up that is already 30 minutes late.....
Procedure for Dealing With Extended Warranties
Shop Management Forum
Nathan from Colorado
This is what I used when I was dealing with this companies on a regular basis.
Step 1. Explain to the customer what the process is going to be. The two biggest things that you want to clarify to them is that they will be responsible for anything the warranty company doesn't pay and that because of the warranty company it will probably take longer to repair the car. In other words, auto repair is still going to take time and cost money. If possible get the paperwork for the warranty from the customer at this time.
Step 2. Get approval from the customer for diagnostic time. The warranty company (with few exceptions) is not going to pay for this.
Step 3. Diagnose the vehicle
Step 3.5 Read the warranty paperwork if you haven't already (and if you have it). Make sure that what you are about to call for approval on is a covered repair, if it isn't, then don't bother calling the company, call the customer. Often the paperwork will tell you how to explain the repair to the warranty company, some things will only be covered if they failed due to another part failing.
Step 4. Write a proper estimate. When you are dealing with a warranty company they will want to know what labor guide you are using, what your labor rate is, what the tax rate is in your state, is labor taxed or just parts? All parts need to be itemized, including hose clamps, how much coolant you need, every detail. Most of these companies will not pay for shop supplies, so if you want to get paid for using a hose clamp, write it down. Parts have to have part numbers and you have to note if they are aftermarket or dealer parts. Use all of your normal mark-ups, just as you would for a regular customer.
Step 5. Make sure you have the vin number/mileage on the work order.
Step 6. Call the warranty company. Yes, you may have to wait on hold for a little while or leave a message and wait for a call back. Once you are talking to a real, live human, give them the information that the want. They are just doing a job, and the easier you make their job, the easier it is for them to say "yes, that's covered and we will pay $XXX" Write down what they will pay, don't take it personally when they say that they will only pay half your normal labor rate and won't pay more than $XX for a part. Maybe they don't pay for gaskets, or fluids, or a million other possibilities. Just write it down. Whatever the company doesn't cover, then the customer will. Once you get to know the individual warranty companies you can figure out the best way to write the estimates. Some companies will pay up to dealer list on any part, so if you can quote the dealer list price for a part, then buy the part for less through worldpac, so be it. Make sure you ask the warranty company how they pay. Do they need a signed invoice faxed to them? Will they send you a credit card number within 24 hours? Is there a number to call if their is a problem?
Step 7. Call the customer. Let them know what the warranty company will pay, and what their share of the costs are. Get their approval.
Step 8. Fix the car
Step 9. Collect the money. This may depend on shop to shop, I never had a problem with collecting the customer's share of the repair then waiting a day or two for the warranty company to pay theirs. If it's a company you never dealt with before, or you got a bad feeling for their professionalism you may want to keep the car until you get paid by both the warranty company and the customer. To me, this would be a case by case decision.
Once you get used to their processes, and learn which companies are good and which are not, these warranties can be good for the shop. If it doesn't work for your shop to jump through their hoops, then simply don't take them.
The biggest problem that I ever had was with the customers who didn't have any money. If you take a customer who bought a car they can't afford then give them a warranty, they are still a customer who can't afford the car. If the customer owns a decent car, has some money, and bought a good warranty because they preferred to even out the costs by paying for a warranty over a few months instead of having a big repair cost at a bad time, then it will probably be a good situation for everybody.
How G.M. is Driving Technicians out of the Trade
Educators Forum
James from Florida
G.M. dealers are moaning that qualified technicians are becoming impossible to find. We have been searching for an A tech for several months and have found nobody qualified. We just hired a dealer tech relocating to Florida from Missouri. We don't know if he really is qualified yet as he is starting tomorrow.
If they want to know why nobody qualified is available, they just need to look in the mirror. Dealer techs are used and abused by both the dealer and the manufacturer. Any recognition, awards. etc. goes either to managers, salespersons or service writers. As techs, we have learned that every time a meeting is called to restructure our pay plans, the result is a pay reduction while they extol the virtues of the new plan. "we're cutting back this time and that time and we expect you to do this new service without pay but you're going to make more money." I'm not one to drink the Kool-Aid as it's hard to see how reducing paid times are making me more money.
Training is available but most techs have learned that training is to be avoided. In order to perform warranty work on a Volt or a Bolt, for example, you need to be trained and G.M. certified. What is your reward for this? You get to do work on the most complex vehicles that G.M. makes for a pittance in paid times along with .3 diagnostics. Virtually all work is warranty with basically no CP labor. Techs have learned that it's better to remain untrained and work on brakes and flushes instead.
G.M. is constantly cutting back labor times for the same job with no justification. For example, reprogramming an I03 radio and loading new graphic files used to pay .9 and there is even a bulletin where G.M. says that this job will take 2.5 hours. It was reduced to .5 and has just been reduced to .2...I can't get the vehicle in the shop in .2.
Now G.M. and it's dealers have instituted a mandatory program where every vehicle MUST have a 27 point safety check performed AND entered line by line into a online program to track. We are not paid to do this and is doesn't matter if the vehicle has 2000 miles or 200,000 miles as all are mandatory. Each vehicle takes a minimum of 15 - 20 minutes to perform. If you work on 8 cars a day, you have just spent 2.5 hours in unpaid labor each and every day.
So, when I see crocodile tears from G.M. and their dealers about how top level techs are getting scarce, I say, ASK YOURSELF WHY?
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