Tuesday, December 15, 2009

Duramax Power Mods and Your GM Warranty

As I started to gather material for this article about the affects of having a Duramax Power Chip or Duramax Power Programmer on your GM warranty, I was dealing with my first casualty arising from GM’s new approach to applying – and, as in my case, denying – its warranty policy. I was not happy about it. The incident involved a good customer, a failed engine and a powertune: that is, a modified engine calibration loaded into the Engine Control Module (ECM) that I had both engineered and installed.
In the past, GM has normally dealt with engine failures on a case-by-case basis. In doing so, it has traditionally been very fair in its approach. Engine overpower failures, that is, failures induced by a combination of customer abuse and huge power programs, are very well defined in a GM bulletin. It is much less difficult to face a customer and deny a warranty for a blown engine when we can show him exactly what happened, and why it is not GM’s fault. But what happens when an engine failure results from a source normally covered under the warranty and the owner has a chip or, as in my case, an aftermarket calibration loaded in the ECM?

As reported previously in maxxTORQUE, all Bosch Engine Control Modules installed in 2006 and later Duramax engines know whether the calibrations they contain have been modified – in any way – from stock. Even the cautious owner who only runs the lightest fuel economy setting in his Duramax will register an ECM change. Despite the fact that such a light power program change is unlikely to cause any damage to the engine, GM may have all the data it needs to refuse warranty coverage on a failed engine when it otherwise would have covered the repairs.
In such a scenario, any damage that occurs is likely to be caused by something other than the slight power modifications. For instance, if an injector starts flowing a little more than it should under a heavy towing condition with a large heat load then, sometimes, a piston combustion chamber will overheat, melting the aluminum and creating a hole from the combustion chamber bowl into the oil-cooling jacket. This almost always causes cylinder wall scoring from collateral damage, requiring engine replacement and at least one new injector to fix the problem. I found myself precisely in the middle of this awkward scenario.

The Investigation Begins

Whenever a failure like this occurs, a technician begins with normal diagnostic procedures. This engine was running reasonably well with no smoke: there was only a bit of roughness from a single-cylinder misfire. The trouble codes stored corroborated the misfire and pinpointed a cylinder. The technician who started the diagnostics ran through some typical checks and then performed a compression test. Noting little to no compression on the misfiring cylinder, he then had to tear down the engine in order to investigate the failure. Upon tear down, he found a hole in the base of the combustion chamber in the piston. Following GM procedures, he meticulously documented all of the damage in the engine. As is almost always the case, photographs were taken to provide evidence of the nature of the failure.
At this point, he reconnected the battery and checked the Calibration Verification Numbers (CVN) in the ECM. He found, as I knew he would, that one or more of the CVN were different from stock, indicating an aftermarket calibration had been installed. The CVN check is part of the process a technician needs to follow in order for GM to make a decision on whether or not they will authorize and pay for an engine repair for the truck. Seeing the CVN change, one doesn’t know exactly what calibrations have been changed or by how much, just that something has been changed. These numbers are reported to GM, along with all the other information gathered. For instance, was there oil coking on the bottom of all the pistons that indicates excessive heat from an over-aggressive powertune? Is there bearing fretting or unusual wear on the wrist pin? Is there polishing on the thrust side of the cylinder wall indicating fuel wash? Is more than one piston melted?
In this scenario, the only signs of damage were isolated to one cylinder and there was only one type of failure, with no other indications of an overpower failure. The root cause of failure in this particular scenario was a failed injector.

GM – Yesterday and Today

How would GM traditionally have treated a scenario like this? From my previous experience, GM more than likely would have approved the engine replacement and one injector under warranty and then given the customer polite but direct instructions regarding his aftermarket duramax power programmer. Something like,
We recognize that a failed fuel injector is a probable cause of the engine failure and we are replacing the engine based on that. However, no matter how mild the modification is, GM does not endorse aftermarket calibrations in your ECM. The technician is returning your ECM to stock calibration and if you wish to continue warranty coverage, you cannot install an aftermarket calibration again.
In my opinion, doing something like this is fair, gracious and a good way to keep the customer base satisfied.
Those were the days. GM’s financial circumstances, however, have changed considerably in just one year and they have apparently affected its outlook on its warranty policy. Today, we are dealing with a company that is desperately trying to plug any leaks in its balance sheets. No upper management team wants to have countless dollars of what they have come to view as avoidable engine repairs on its books: regardless of whether replacing an engine appears fair or not. Same engine, same damage but GM has found a way to deny coverage for those of us who are caught using aftermarket powertunes.

A holed piston from a Duramax engine with a clear-cut overpower failure. Note the unusual flame pattern on the top of the piston.
Sifting Through the Paperwork
So what does GM’s warranty policy stipulate for a scenario like the one in which I found myself? Consider this excerpt from the Light Duty Limited Warranty and Maintenance Schedule booklet from a 2009 Chevrolet Silverado:
This warranty does not cover any damage or failure resulting from modification or alterations to the vehicle’s original equipment as manufactured or assembled by General Motors. Examples of the types of alterations that would not be covered include cutting, welding, or disconnecting of the vehicle’s original equipment parts and components.
Additionally, General Motors does not warranty non-GM parts and/or calibrations. The use of parts and/or control module calibrations not issued through General Motors will void the warranty coverage for those components that are damaged or otherwise affected by the installation of the non-GM part and/or control module calibration.
This language specifies that warranty coverage is void for components that are damaged or otherwise affected by the installation of the non-GM part. On the surface, this wording might be interpreted to mean that GM would have to prove whether or not engine damage was caused by an aftermarket calibration.
In support of that perspective, GM has an extensive bulletin that defines very clearly what is considered engine overpower failure and what is not. Why go through the trouble of so clearly defining an overpower failure only to then deny all warranty claims involving a modified engine – whether or not the damage was caused by the overpower failure?
The bulletin explicitly explains that an engine has to manifest at least three of the six criteria noted below in order for the engine damage to come under the category of an overpower failure: 
  • Piston cracked parallel to wrist pin: piston cracked in lip area; hole in piston connecting top of piston to oil cooling channel.
  • Melted Pistons: lip of combustion bowl melted; top of piston melted or missing.
  • Cross hatching polished off cylinder wall: cylinder wall missing crosshatch on major thrust face of cylinder below ring belt travel.
  • Piston pin bore, wrist pin, and rod bushing: scoring in upper piston pin boss/black discoloration/oil coking; wrist pin wear; rod bushing surface worn and discolored.
  • Carbon coking to underside of piston: discoloration of underside of piston; discoloration and carbon coking buildup on underside of piston between piston pin bosses.
  • Accelerated rod/main bearing wear: fretting on backside of bearing; bearing surface distressed.
Our engine failure scenario demonstrated only one problem: a hole in one piston with a crack just starting to develop parallel to the wrist pin.
Absolutely none of the other criteria occurred, leading myself and the technician involved to conclude that an injector was the ultimate cause of the engine failure – indeed the bulletin itself describes a fuel injector problem as a likely cause in this scenario. While it is true that the powertune – due to the moderately increased fueling at full engine load – could contribute to an earlier failure than would have otherwise happened I would estimate, in my case, that the failure would have been delayed by no more than 500 miles.
Even though the evidence of the type of failure we were dealing with was so clear, I was nervous. Did I make a critical error in the tuning? Would I have scores of angry customer’s with failed engines coming back at me? I poured over the tuning again and again looking for some critical fault, but could find none. In point of fact, this was the first and only engine failure I have seen on a truck that was running my tuning. All indications kept pointing back to a manufacturing defect – in this case a failed fuel injector – as the root cause of the engine failure. I could only come to the conclusion that GM should warranty this defect and the subsequent engine damage.
A melted Duramax piston from the same engine demonstrating an overpower failure. It takes a good deal of heat to melt that much aluminum.
Legally Speaking...
There can be a number of reasons why GM would decide not to pay warranty costs for anything that has had aftermarket modifications. First, consider how many overpower failures GM had already paid for prior to this information coming out – it must be stinging from that. For several years, GM replaced failed engines without any way to really determine if there was any aftermarket tuning. Considering that a new Duramax costs around $12,000, not including labor, the expenses add up very quickly. I have heard rumors of warehouses full of returned, failed Duramax engines that the engineers had to pour through to determine the real cause of failure. After that experience it would be easy to take a position on the opposite extreme. Now, of course, we are talking about a company that has entered bankruptcy protection. There is no question that the motivation is there to tighten up warranty spending.
Though we can only guess why GM has taken the path of denying seemingly valid warranty claims, there is no doubt that they are actually doing it. Already I have heard of cases of denied warranty claims from technicians and dealers who are not very liberal in their viewpoint. Most importantly, GM has a strong legal case to deny warranty coverage when there is evidence of virtually any modification made to a vehicle.
To explain more fully, let’s look at the limitations of GM’s warranty obligations from another angle. Consider the following hypothetical scenario:
A customer purchases a completely new truck and installs GM approved accessories, namely mud-flaps and step boards. After driving that truck for 30,000 miles and maintaining it according to the maintenance schedule at GM approved maintenance centers, the customer decides that he wants to replace the tires. The tires that came with the truck are just too small for his liking; he wants something with a little more aggressive tread. He moves from the stock 245/75R16’s to a set of 285/75R16’s. This is a classic tire swap that requires a torsion bar lift, new front shocks to allow more travel – and he gets it aligned for good measure. This truck continues on for another 20,000 miles happily until an inner tie-rod shaft breaks, causing an accident.
Several things could have weakened the inner tie-rod end so that it would break: damage from off-road stresses, damage from a technician who overtightened the tie-rod end jam nut, damage from a hyper-extended suspension system or damage from applying too much engine torque in 4WD to name a few.
In the almost inevitable legal woes that would follow such an scenario, GM’s lawyers may be required to explain why the accident was not caused by a manufacturing defect. Short of sending the truck to a laboratory, it would be very difficult to come up with a definitive answer as to exactly why the tie-rod end shaft failed. But GM would not have to go that far. All it would have to say is that the customer modified the vehicle so that it was operating outside the envelope that GM had validated and tested as safe. No matter what the actual cause of failure, GM cannot be held liable for it because it has not tested and approved the vehicle in its current configuration. There can be no question that the tie-rod went through stresses for which it was not designed as a result of the new tires and the vehicle modifications that they required. Regardless of whether there was actually a manufacturing defect in the tie-rod shaft or not, GM is safe to stand behind that legal argument. As a manufacturing company, it is simply not possible to over-engineer every component to deal with every modification that a customer may make to his vehicle.
This is a view of the engine calibrations that have been loaded into this ECM, as read by the Tech II diagnostic tool. The numbers on the right are the CVN, which can tell GM whether or not the ECM has been loaded with an aftermarket calibration. In this instance, my personal truck, all of the CVN numbers do not match up with the stock numbers that GM provides through their Service Programming information service. That is because of the fact that my ECM has been reflashed several times with modified tunes.
This same principle can be applied to any aftermarket modifications that are made to the vehicle. An aftermarket tune of absolutely any variety, no matter how little it varies from the stock tune, takes the engine out of the operating parameters that GM has tested and is willing to stand behind. GM cannot be held legally liable for what happens to their product after a customer modifies it. Therefore, GM is within their rights to void the powertrain warranty on a vehicle if a customer makes a change to the powertrain.
Now let’s go back and carefully check the wording of the warranty booklet. It says that the warranty coverage is void for those components that are
damaged or otherwise affected by the installation of the non-GM part and/or control module calibration
That phrase otherwise affected can be interpreted very broadly, and provides a basis for GM’s reasoning. What components can be considered affected by an aftermarket Duramax power program? Really, anything in the powertrain can potentially be affected by the additional stresses caused by increasing the power output of the engine. It does not really matter how much additional power or to what degree the parts are affected, just that they are affected. To simplify the wording in the warranty booklet, we could say that GM can void the warranty for those components that are affected by the installation of a non-GM control module calibration. In other words, GM can void the powertrain warranty if there is any evidence of an aftermarket control module calibration regardless of whether or not there has been any failures. Yes, if a dealer sees a plug-in chip or evidence of a programmer, the powertrain warranty can be voided right then and there. This has broad implications for those of us who take pride in modifications to our trucks.
This is the damaged piston from the engine referred to in this article. A clean hole in the combustion chamber that caused the wristpin retainer ring to come out, creating the heavy scoring on the cylinder wall. This was the only damage manifest in this engine. Typical overpower failures will have more than one holed or melted piston with a major crack down the centerline. All indications were that this engine failed from a fuel injector failure.

What About the Magnuson-Moss Warranty Act?

The Magnuson-Moss Warranty Act is often brought up in a discussion of aftermarket parts and modifications. It has been interpreted in discussion forums and on aftermarket manufacturers’ web sites to mean that a manufacturer cannot deny a warranty claim due to an aftermarket part unless the manufacturer can prove that the aftermarket part actually caused the specific failure being dealt with. In reality, the Act does not even come into play in a scenario like the one in which I was involved.
Here is an excerpt from the Magnuson-Moss Warranty Act:
No warrantor of a consumer product may condition his written or implied warranty of such product on the consumer’s using, in connection with such product, any article or service (other than article or service provided without charge under the terms of the warranty) which is identified by brand, trade, or corporate name; except that the prohibition of this subsection may be waived by the [Federal Trade] Commission if –
(1) the warrantor satisfies the Commission that the warranted product will function properly only if the article or service so identified is used in connection with the warranted product, and
(2) the Commission finds that such a waiver is in the public interest. The Commission shall identify in the Federal Register, and permit public comment on, all applications for waiver of the prohibition of this subsection, and shall publish in the Federal Register its disposition of any such application, including the reasons therefor.
(Magnuson-Moss Warranty Act, Title 15, United States Code, Section 2302, subdivision (c)).
Essentially this clause prohibits manufacturers from writing their warranties to limit consumer use of a particular brand of non-manufacturer service or maintenance part – for example, oil filters and oil changes, air filters and the like. It was intended to prevent tie-ins or using the warranty policy to guarantee further income for the manufacturer or dealer.
Going back to the wording in GM’s new vehicle warranty policy, it is clear that GM does not void warranty just because a consumer used a different brand of service or maintenance item. GM is protecting itself against customer modifications or alterations from the vehicle’s original specification. GM clearly states that it does not warranty non-GM parts and/or control module calibrations and the parts affected or damaged by such parts. This is within its rights under Magnuson-Moss. GM can and does stipulate that non-GM branded parts, as opposed to regular service/maintenance items, that modify the vehicle from its original specification are not covered by its warranty.
There is a clear difference between parts or services that modify and those involved in regular service and maintenance. GM’s new vehicle warranty policy addresses the former while Magnuson-Moss is talking about the latter. Keep in mind that GM pays well to have lawyers pour over their documentation to ensure that it conforms to federal law. GM’s position on aftermarket modifications is well defined and legal.
This engine – what is left of it – is an example of a clear overpower failure. Note the extreme nature of the piston melting and damage, spread over more than one cylinder. Believe it or not, this engine actually did run and – less difficult to believe – produced prodigious amounts of smoke and noise.

In the Real World

Taken to its logical conclusion, this policy could be used to void the powertrain portion of a vehicle’s warranty with any exhaust system change, intake upgrade, aftermarket Duramax power program or Duramax power chip, transmission shift kit, lift kit and so on – with or without a component failure. In the real world, some dealers will not go that far. A large portion of their customer base have made some kind of modification to their trucks due to the popularity of aftermarket accessories. They need the customer base that they have, they can not afford to make customers angry. For now, GM is generally only asking about aftermarket modifications when it is faced with paying for a major component failure.

Warranty Denial

Inevitably however, some technicians and dealers will take a knee-jerk reaction to aftermarket modifications. In other words, no matter what the root problem of an issue is, they will deny warranty based on the fact that they discovered an aftermarket power-adding device or program. In one instance that I monitored, another dealer posted a warranty denial alert for a truck that was running rough and making black smoke. They provided excellent detail in their information regarding injector return fuel rates and operating conditions. In fact, the detail was so good that it was easy for an experienced technician to diagnose the problem: contaminated fuel. This issue is one that we see often enough around Alberta, Canada because some oilfield workers are in the habit of fueling their trucks from the large fuel tanks on oil rigs. Those big tanks can contain a witches brew of questionable diesel fuel due to condensation and other factors.
In this case, I would anticipate that the customer would be liable for the repair and would have to fight it out with his fuel supplier for compensation. The severity of injector damage varies from one failure to another, but the repair generally entails replacing all the injectors, flushing the fuel system and replacing the fuel filter – at a cost typically ranging from $5,000 to $12,000 depending upon the model year. The dealer, who seems to have fallen under the influence of GM’s new approach to warranty coverage, chose to focus its attention on the aftermarket plug-in chip instead of the obvious fuel contamination. They disconnected the chip and tested the truck again with no improvement. At that point they quoted a complete set of injectors and a fuel injection pump. The customer removed their vehicle from that dealer and went elsewhere for repairs.
As I would expect, the dealer posted a warranty denial alert in the system. But what was the warranty denial alert for? Was it for bad fuel that had damaged the fuel system? The alert actually said nothing about bad fuel and only mentioned the brand name aftermarket chip that was installed on the truck. The photos posted with this warranty denial alert do not show a fuel sample, fuel filter cutaway or anything that relates to the actual cause of failure. Instead, there is only a photo of the truck, the instrument cluster and the aftermarket chip. Looking at that specific alert, it is very easy to infer that the dealership denied warranty coverage based on the fact that there was an aftermarket chip installed and not because of the actual cause of failure: bad fuel. At this point there is a warranty block in the system and this customer no longer has warranty coverage on his engine. The rest of his powertrain warranty had already expired, otherwise it would have been affected as well.

The New GM

Thanks to GM’s new approach, scenarios like this one are beginning to pop up between dealers and customers. A plug-in chip is easy to see and to point fingers at, especially given its history of abuse – even if only by a relatively few number of owners. An aftermarket Duramax power program, invisibly loaded in the ECM, takes more effort to find and a technician has to have a good reason to go looking. In most circumstances, a technician is not very likely to break routine in order to look up and compare CVN numbers when diagnosing a problem whose symptoms will lead him in a different direction. Still, bringing a truck to the dealer with either an aftermarket power program or a Duramax power chip does create the risk of loosing powertrain warranty coverage. Be aware of that risk when considering any modification to your truck.
GM has recently released a couple of bulletins and other internal documents that identify procedures for the dealer to take when an aftermarket calibration is suspected. Technicians are instructed to inspect for aftermarket calibrations when there is any unusual driveline component failure. One internal document states that GM’s policy is to cancel the powertrain portion of a customer’s warranty if an aftermarket calibration or power adding device has been confirmed on the truck – with no second chances or warnings of any kind. It also states that even if the non-GM calibration is removed, the warranty will still remain canceled due to the fact that it could have adversely affected other powertrain components.

Can I Hide Modifications from GM?

Yes and no. There are ways that a customer can try to hide that they have made any modifications to their truck. If you have an aftermarket chip, just disconnect it before taking it to the dealer. No trace of the chip will be left in the ECM. If you have an aftermarket Duramax power program and need to take the truck in to the dealer, you can purchase another ECM – at about $1,000 – loaded with the stock program and install it before taking your truck to a dealer.
Still, the safest option is to simply wait to modify your truck until after the warranty coverage has expired. this is true because even if you take safeguards like those listed above, it is still possible to detect evidence that the power output of the engine has been altered. GM has now made us aware of another alternative for detecting a powertune. It resides in the Allison transmission control module (TCM). In order to properly shift the transmission, the TCM makes a calculation to estimate the actual torque output of the engine in addition to what the ECM communicates as its desired torque output. The Allison TCM requires these data in order to allow for variations while maintaining shift quality and timing. Over time, modifying the torque output of the engine changes this estimated torque calculation, with the Allison adapting to the new torque output of the engine. An experienced technician can tell just by driving the truck if there was an aggressive powertune and the truck has been returned to stock – the shifts are very crisp, almost punishing. That is a result of the transmission torque calculation. Less subjectively than driving the truck, a technician that cannot find any other evidence of an aftermarket Duramax power programmer or Duramax power chip can take a snapshot of the torque calculation stored in the TCM and send it to engineering for analysis. Engineering will then be able to determine if a power program or chip has been installed and then removed prior to the visit to the dealer. This evidence takes considerable effort to produce and will likely only be a technique used on a very expensive and suspect failure. The point is that it is virtually impossible to completely hide an aftermarket power program or chip.
For those of us like myself who develop and sell powertunes, GM’s new approach does put a crimp on our business with vehicles still under warranty. For those customers who enjoy the benefits of improved fuel economy and driveablility that come with a quality powertune, this policy is truly inconvenient and potentially costly. Considering that Duramax powertrain mechanical failures are actually quite rare among those of us who do not abuse their trucks, you may be willing to shoulder the warranty risk involved.


What happened with the failed engine mentioned at the outset? GM flatly denied any warranty coverage, period. We did pursue several channels internally, but the answer was the same from all involved and was delivered without any sympathy. That left our customer with a wrecked engine and at least one injector that needed to be replaced. In the end, the customer, the dealership and I worked out an equitable arrangement. The customer left happy but a little shell-shocked about GM’s blunt refusal of warranty. He has decided to run stock tuning now for the remainder of the truck’s warranty. In this instance, the only part of the warranty that had not already expired was the Duramax engine warranty, which is still in effect due to the fact that the entire engine has been replaced. The bottom line: any modification that a customer decides to make to their Duramax-powered truck is done entirely at their own risk, however slight that risk may be.

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