How I survived catalytic converter theft

Hack-Mechanic-CAT-converter-theft lead
Rob Siegel

I’ve written multiple times about my 2008 Chevy 3500HD Duramax diesel. How my former engineering job had largely abandoned the 28,000-mile truck when the company closed the building … how it became a gag-worthy mouse-infested mess … how I made a criminally low offer for it (that took four months to be accepted) … how I largely de-moused it … and how I thought I’d use it to buy and tow home a whole bunch of cars but instead have only moved two cars and a bunch of BMW parts with it, helped my niece move, made cardboard and motor oil recycling runs in it … and how I park it in a $50/month rented space about a mile from my house to make space in my driveway.

As if that isn’t enough, I never expected to add, “… and how I had to deal with a stolen catalytic converter.”

My discovery of the theft happened in a funny way. Prior to Thanksgiving, my wife had arranged to borrow one of those tall outdoor heaters from a friend so that we could put it on the back deck in case someone wanted to escape the crush of people inside for a bit—maybe have a beer and a private conversation outside. So, I walked over to the truck’s parking space (which is in the parking lot of a dance studio located right next to what used to be the town dump but is now the recycling depot), reconnected the batteries, and fired it up.

As soon as the truck was running, I could hear an unusual whirring sound, as if a blower fan was running. I never for a moment thought it could be a cut catalytic converter, as it wasn’t a big woof-y, truck-y exhaust sound. It was more the kind of air-movement sound a cooling fan makes if the viscous clutch is locked up. I opened the hood, but the sound wasn’t coming from there—it seemed to be emanating from below, near the center of the truck. I crawled under and guessed that the source of the whirring was the transmission. I realized this was the coldest it had been outside this season, and that I hadn’t changed or even recently checked the transmission fluid. Maybe that’s all it was.

So, I drove the truck on a quick errand to see if warming it up made the noise go away. It didn’t. When I got home, I looked for my mechanic’s stethoscope but couldn’t find it. I crawled under the truck again, listened to the noise, put my hands on the transmission pan, and convinced myself the noise was indeed coming from there. To avoid any damage, I decided not to drive it the 20-ish miles to pick up the heater and instead used the Winnebago Rialta (the little VW Eurovan-based RV). I made a mental note to, after Thanksgiving, take the truck into the local transmission shop, which had looked at the transmission on my Suburbans years back.

The Monday after Thanksgiving, I set the plan in motion. I started the truck, crawled under it a third time to verify the presence and location of the noise, then drove it two miles to the transmission shop. I described the “whirring” sound to the shop owner. “Whirring, not whining?” he asked. I nodded. He looked perplexed and came outside to look at it. He stuck his head under the truck, and immediately said the last five words I expected to hear:

“Your cat has been cut.”

Cat converter missing cut pipe
There’s supposed to be a catalytic converter in that 17-inch empty section. Rob Siegel

I was astonished—both that it had happened and that I had completely missed it. In my defense, aside from the exhaust sounding pretty much normal (particularly with the windows up), the cut sections of pipe where the catalytic converter once resided are close to the inside of the right frame rail. Even after the guy told me what had happened, I had to crawl way under and look up and to the right to see the cut pipes. On the drive back from the transmission shop, I did notice that I could hear more spin-down noise from the turbo on deceleration than I remembered. I assume that it’s the turbo’s presence in the exhaust (rather than having an open pipe coming down from the exhaust manifold) that made it not sound like a straight-piped menace.

Cat converter missing cut pipe end
The rear section where the cat was cut … Rob Siegel
Cat converter missing cut pipe end
…and the front. Rob Siegel

Catalytic converters are stolen because they contain the valuable rare metals platinum, rhodium, and palladium to catalyze (react with) the exhaust. The scrap value is widely quoted online as being between $300 and $1500. Toyota Priuses are prime targets for cat theft because the hybrid vehicle’s cat contains a higher concentration of these precious metals than most other cars. Catalytic converter theft has been a hot topic for awhile, but it has accelerated dramatically in recent years, reportedly because mining of these materials was affected by the COVID-19 pandemic. In early November, there were news reports of federal authorities busting a company in New Jersey and arresting a nationwide ring of cat thieves, and there is legislation advancing at the state level to engrave the Vehicle Identification Number (VIN) into cats as a theft-deterrent. Diesel trucks used to be overlooked due to their cats working differently—they don’t contain rhodium, and thus having much lower recycling value—but their high ground clearance and easy cat access has recently made them targets.

I, of course, never gave any of this a second thought. I live in Newton, Massachusetts, one of the safest small cities in the country. I haven’t had a vehicle vandalized since we moved here from Boston 30 years ago. And I don’t own a Prius.

When it happened, of course, hindsight kicked in. This is a big dually truck that you can practically limbo under while wielding a battery powered Sawzall. My parking spot in the lot next to the town recycling center is in an industrial area. And the fact that many people likely saw the truck sitting for weeks made it a likely target. It’s a wonder it didn’t happen sooner.

Random parking lot cars on sunny bluebird day
The truck in what I now realize was a vulnerable parking location. Rob Siegel

So, after you shake your fist and swear at the lowlifes who cut the cat out of your ride, what do you do? The basic sequence is:

  1. File a police report. My local police station is processing several cat thefts a day (“mostly Priuses”).
  2. Contact your insurance company to find out your coverage. If you file a claim, you’ll likely need the police report, which is why I listed it as the first step.
  3. Learn what the laws are in your state. That may be a rude awakening. California, for example, requires the catalytic converter in all vehicles to be either the OEM part or an aftermarket State Air Resources Board-approved unit, and prohibits generic catalytic converters that are based solely on physical shape, size, configuration, or pipe diameter. Other states are likely more accommodating, but you’ll need to check.
  4. Get several estimates. As with nearly any repair, having it performed at the dealership will be the most expensive option.

Be aware that, in addition to state laws, certain Federal laws are in play. The first is that, not surprisingly, it’s illegal to remove a cat and replace it with any kind of bypass pipe. Another is that it’s illegal to sell or install a used catalytic converter unless it has been properly recertified, which involves testing and labeling. I doubt that black helicopters are going to swoop down on you if you buy a used cat and install it yourself, but what it means is that established independent repair shops likely won’t want the risk of offering it to you as an option. And technically, it’s illegal to be operating the vehicle with the cat removed, although it would take particularly bad luck on your part for that to be discovered, and a police officer would need to be having a particularly bad day for you to be written up about it, especially if you had the copy of the police report of the theft with you.

Regarding the hazards of short-term driving of the vehicle with the cat cut out, there are several issues. The first is whether the remaining sections of the exhaust are dragging or scraping against anything, as along with the cat, the thieves may have chopped out a hanger that supports the center of the exhaust. If you hear scraping, unless you’re a mechanic and can either ascertain that it’s a trivial issue or wire the exhaust in place, don’t drive the car—call for a tow.

Then there’s the health issue of the presence of exhaust fumes that are now likely gushing out directly under the car. This is the kind of thing you don’t want to be wrong about, particularly if you’re about to drive in traffic with children or infants as passengers. Err on the side of safety. The third is whether it’s harmful to the engine to drive with the exhaust open and the cat missing. For short distances, like to get the car repaired, it’ll likely be fine, but without the cat to clean the exhaust, the oxygen sensor after it (if it’s still there after the car was butchered with a power saw) is going to give readings to the vehicle’s electronic control unit (ECU), which will likely cause the check engine light (CEL) and potentially other dashboard indicators to come on. Depending on the car, it’s possible the ECU may throw it into a reduced-power limp-home mode. So, it’s best to drive it as little as possible.

In my case, I’m blessed with being a do-it-yourselfer and not needing to have the truck repaired quickly. After looking at the problem for a few days, here’s how it’s panning out:

  • The part that was taken—the OE General Motors “oxidation catalytic converter” (#15283013) used on trucks with Duramax LMM engines from 2007 through 2010—lists for $1837 with a $400 core charge (which, of course, I don’t have, BECAUSE IT WAS STOLEN). Discounted online dealer price is as low as $1200, but with the core charge, shipping, and taxes, it comes to nearly $1750. Plus, there’s a gasket, a clamp, and a hanger. You can see how if, you took it to a dealer, you could get quoted three or four thousand dollars for the job.
  • I have never, ever, deleted a catalytic converter from a car, and I have zero interest in starting now (yeah, I know; someone else already deleted it, but I need to do something to be able to drive the truck, and that is not going to be a bypass pipe).
  • I have a $2000 deductible on my truck’s comprehensive insurance. This means that I won’t be filing a claim and instead will either fix it myself or try to find some small low-overhead shop (e.g., not a dealer) to do it.
  • The original cat on the truck is welded between two pieces of double-walled 4-inch pipe. On the front end, it’s attached to the engine with a heavy-duty band clamp, and on the back end, has a four-bolt flange that’s bolted to the Diesel Particulate Filter (DPF). So, if I want to replace the whole cat assembly myself, it looks like it comes off fairly easily (or as easily as any old exhaust bolts come off).
Cat converter exhaust joint clamp
The band clamp at the front of the cat pipe. Rob Siegel
Cat converter missing cut pipe end
The top two of the four bolts of the flange holding it to the DPF. Rob Siegel
  • When the cat was removed, so was the post that a rubber hanger attaches to, so the front part of the back of the exhaust is currently just resting on a frame cross-member. I’m lucky that it is, or the whole thing could’ve tilted down and ripped out the lines plumbing the DPF. Even the cat notwithstanding, I’d be foolish to drive it anything but short distances at low speed until it’s properly hung.
  • Instead of replacing the whole section, if I want instead to have someone weld a new compatible aftermarket catalytic converter into the existing pipes, it looks to me like there’s still enough of both pipes present to allow it. That is, if I can find someone to do it. I called two shops that have done custom exhaust work for me over the years. The first one won’t touch it, because they don’t know that much about diesels and aren’t sure which cat would be needed to properly play with the DPF. The second shop said they’d need to see it but ballparked it at $1500 job and said they couldn’t get to it for two weeks because—ready?—they need to install new cats in a fleet of 56 city trucks, all of which had them stolen.
  • A vendor on eBay sells recertified cats for GM trucks and has the one I need in stock, shipped, for about $800. That price initially went tilt with me, but now is looking pretty good.
Catalytic converter pipe
The $800 eBay recertified solution. Courtesy KGC Warehouse
  • Let’s say that, for the sake of argument, there wasn’t a law against installing an uncertified used cat, and that I went looking for such a thing as a less expensive option. What I may or may not have found after searching for several hours on Facebook Marketplace and Craigslist for a cat for a 2007–

10 Duramax LMM was one guy in northern Maine selling a complete low-mileage exhaust system for $650. When I hypothetically asked whether he’d sell me just the cat and ship it, he hypothetically declined.

  • I also may or may not have seen ads on Facebook Marketplace and Craigslist for inexpensive used cats from the previous generations of Duramax diesels (the ones before the DPF became a federally mandated component), and while the bends of the pipes and the connections on the ends look the same as mine, they’re not listed as cross-referencing. I posed a question on the Duramax Diesel forum, but no one answered it definitively. A friend who knows diesels (but not Duramaxes) says the cat on a diesel with a DPF is a diesel oxidation converter whose job is to oxidize the fuel being injected into the exhaust to create enough heat to burn the soot out of the DPF, and that the previous generation of cat wouldn’t do that. Thus, it’d be iffy to buy one of them. If I saw them. Or was even looking for them. Which I may or may not have been.
  1. Let me cut the weasel-wording. I’m a practical guy who tries relentlessly to contain cost on 13 vehicles, and this is a truck I barely drive. If the only two options were 1) Take it to the dealer and pay up to my $2000 deductible, or 2) Entertain the possibility of buying some cheap, used, high-mileage catalytic converter assembly that would hang and seal the exhaust but might not perform the intended emissions function due to age or compatibility or both, you can see how the second option might be tempting. And if my truck was high-mileage, finding another high-mileage cat like the one that had been taken might seem justified. However, this is a 28,000-mile vehicle. Even the legality notwithstanding, the idea of finding and installing a $150 200,000-mile cat just doesn’t sit well with me.

For all these reasons, I pulled the trigger on the $800 eBay recertified cat. After a bit of back-and-forth, the vendor (KGC Warehouse) was kind enough to knock $100 off the price, which was greatly appreciated, especially considering that it was the only correct click-and-buy recertified cat I could find.

Lastly, there’s the question of preventing it from happening again. In the Prius world, there are now click-and-buy cages and shields you can install that make the cat more difficult to remove. I haven’t seen such a product for the truck, but it’s probably not too difficult to fabricate an aluminum plate. But really, I’m hoping that simply parking the truck down at the end of the driveway of my house on my sleepy dead-end street instead of in the highly visible parking lot next to the town recycling center will make the difference.


If you’re like me, you absolutely hate to be put into a situation where you feel put over a barrel and have to pay an insane sum of money simply to regain functionality that you already had. After all, this isn’t something fun like fresh paint or a hot engine or new wheels or new Recaro seats—it’s a freaking catalytic converter that some scumbag stole. At least I’m getting out of it for closer to washing machine money than Hawaiian vacation money.


Rob Siegel’s latest book, The Best of the Hack MechanicTM: 35 years of hacks, kluges, and assorted automotive mayhem, is available on Amazon. His other seven books are available here, or you can order personally inscribed copies through his website,

Read next Up next: 12 great automotive gifts to fit every holiday budget


    For as often as you drive the truck, just remove the thing & reinstall when needed. You’d eventually get pretty quick at doing that. Then you could just leave it at that parking lot.

    GOD HELP THEM if I catch them doing it in my driveway. Gonna call my insurance to see if i have attorney coverage after i get through with them.

    Police in my town stopped a panel truck for a minor infraction, two illegal aliens with no license or registration and lo and behold the truck was filled top to bottom with stolen cats.

    I wonder if engraving the VIN in the replacement cat would be of any use? Probably not as a potential thief wouldn’t notice till after stealing it. The way to go seems to be legislation so everyone knows they are all labelled. Hopefully that is coming soon!

    Owners were doing that in New Jersey last year. It didn’t seem to do any good. The problem is that the recycling companies already know the cat was stolen and they don’t care. The only time labeling the cat does any good is if the police happen to catch the perps before they get to the recycling company.

    Considering the strong demand used vehicles, and that it’s seldom used, I’d sell the truck and just rent one whenever I need.

    Any of you in states using the CARB regulations are pretty much screwed. You will be forced to used replacements that have approved numbers on them. Yes they are more expensive.

    Then you will have issues as some of these converters are on back order. Many are on
    Long back orders.

    This is an issue with no simple answer. Even if they catch these thieves they will just let them go. Heck you can hit someone over the head with a ball bat and chop up a McD in NY and get out on no bail.

    The only real solution is one to park inside a locked building.

    Or in the case of a truck like this build a cement block square area that you can park over but they can not get over. I know it sounds like a lot but they will be back and you are not boing to want to crawl under a truck in January to put a converter on just for one trip.

    The California law is nuts as generally most universal converters will more than meet the regulations but since they were not tested you can not use them.

    If it were someone very similar to me in a hypothetical replacement, that person would probably replace the cat with something that looked a lot like a cat but wasn’t… hypothetically speaking.

    … so long as the vehicle need not be inspected by the state annually.

    Many states have no inspection requirements regarding exhaust or at all – FL being one of them. BUT if the vehicle should happen to have “historical” or “antique” license plates….hypothetically of course – the exhaust test is not included in a State required inspection. So ie a 1968 car would be exempt in NYS.

    So hypothetically an old truck or one with “historical” plates would be exempt and if you drove w/o a converter only your guilt would force you to put one in. Hypothetically of course. I have buddies with vehicles with “historic plates” which are hardly “historic”.

    A friend of ours left us a 2002 Deville Cadillac. The window controllers didn’t work and the AC was shot but the body was straight, and as I sat in the big overstuffed leather seats I knew the car was something special to someone.
    The car drove ok, radio was good, it had newish tires, I was well falling for her. The gal who gave us the car had terrible luck so my wife was already leaning the wrong way, plus I was up to my eyeballs in other projects, so after a lot of this is just the one that got away, feeling we regretfully put an add in Craigslist, with a very reasonable price of $900.00.
    The offers went crazy and everyone wanted the Cadillac! The first buyer had a tow dolly and asked if the catalytic converter was still there, I said I thought it was at which point we jacked it up and low and behold there was a straight pipe where the converter used to be. The buyer told us that the converter would alone sell for $900 and the rest of the car was pure profit. No one else seemed to want it after we truthfully had to tell them there was no cat and we ended up selling it to some kid for $500.
    My lesson is that it is powerful incentive to stick with pre 1972 stuff and avoid the problem altogether!

    Why pre-1972? Most American cars did not have cats until 1975, and some not until a few years later. And, those old cats seemed to be over-engineered, and have rarely failed over the decades.

    I have a 75 full-size GM car, catalytic converters is still working as well as the day I got it. The only work I ever did was move it from the trunk, to a shelf in the garage. I didn’t take it off, I didn’t weld up a pipe, I just bought an old car.

    And if you’re worried about air quality, you should never grille with charcoal because it is 5x more polluting (HC and PM-5 through 10) than an old pre-DPF HD diesel truck.

    We will all have electric grills soon – and people will swear up and down that being electric doesn’t take any of the thrill out of grilling

    Can’t have a wood fire in the fireplace most every Christmas in Phoenix. No burn days they say. The temperature inversion layer has a thick layer of haze the morning of the 26th. What’s ironically worse, because fireworks were lobbied to be legal, there is zero enforcement, and we can buy them Christmas to New Year’s Eve, the morning of Jan 1, the air is WORSE than Dec 26.

    Electric grill with fat separator? It’s coming. Think: extra large George foreman grille.

    You missed some nice driving! I bought a 2002 Deville for $3800 c5 years ago to save putting miles on an expensive truck and loved the car so much I’ve since bought two other matching 2005 Devilles for another $6k combined for our daily drivers. About 500,000 miles combined for 3 very nice driving cars costing c$10 total. The 02 will eventually be a parts car for the other two, for now it’s my “dirty” errand car while the others are our road cars. Seriously I get 20-24 MPG on the highway with nice cool air blowing up my backside in the cooled seats in the very hot Arizona summers. They do take some ongoing maintenance, especially the servo motors on the HVAC under dash, but OMG, they ride so nice and quiet I can’t even think of buying a new car at today’s ridiculous prices. I don’t mind long drives at all, zero depreciation per mile baby!

    I think the John Nichols lesson is pretty valid…
    I have a ranch truck and a Jeep parked out in a covered barn area that has no doors. They are really seldom used, especially in winter, when the ranch is pretty much in hibernation. I check on them often, but live in fear that someday I’ll go out and find that the cats have been stolen (and I’m not referring to the barn-mousers who live out there). The numbers in Rob’s story are pretty scary considering the relative value of the vehicles.
    Considering that a great many of the people involved in the chain of activity in stolen cats are unscrupulous crooks, I find it silly to think that engraving VINs on a part will dissuade theft. Do burglars worry that things have serial numbers on them? No. They do not. An identifying number on a vehicular part that is just going through the hands of “fences” to an ultimate end of smelting will easily slip through any “laws” intended to stop them. Likewise, building a “cage” around a cat seems kinda short-sighted, IMO. The crook is under the vehicle with a handy metal-cutting device. Don’t think he will just go ahead and cut the cage off and then the cat? Maybe in some cases where the additional time needed will be risky, but honestly, in a large percentage of cases I’ve heard about, the victim has no idea when it happened or how long it took. So a few extra minutes will not deter the criminal from reaching the goal in most instances.

    One Denver garage where I priced a metal cover over the cat area to prevent theft would have run $750+, but worth it, considering the cost of a cat. One person on a local NextDoor neighborhood site showed an alarm system intended for a house alarm, that he installed under his vehicle with motion detection, a piercingly loud alarm and a wireless signal to your alarm device inside the house, that was part of the kit, a much better idea than cages, red paint or etching something on the cat. Certainly not the end-all solution, however, .
    I hold my breath when I start my truck up in the mornings, fearing the loud sound from a missing cat. Theft of cats is very common in Denver.

    Goodnight! There was some serious brain damage that took place while writing that article. If I find a $800 cat to fix my problem, it is done yesterday. What’s not to like?

    Of course I do not write articles for Hagerty for a living.

    I carried a 1k deductible from about 1986 – 2013. Saved a fortune on premiums. One claim in 27 years- drove over a wheel on an Interstate and it ripped out all of the plastic under skirting. Since 2013 I self insure my 03 Honda which now has 200k. Never been in an accident but the car has been hit in parking lots….hit and runs. I have paid out of pocket in 9 years maybe $1,500 for body work including paint. Pay in cash and tell the body shop “my fault, my wife can’t find out and she controls all the bank accounts”.

    Anyhow, I saved thousands of dollars in premiums by opting for the 1k deductible. Consider self insuring for fire, theft and collision if the book value of your car no longer warrants insurance payments.

    I’ve advocated to anyone that will listen, for making it a crime to possess a catalytic converter that is not installed in the vehicle.
    I see ads on all the sales sites and social media offering money for your catalytic converters. I’m my area in Texas, the USA/Mexico border, almost every car on the road is straight piped because people will sell the cat or it’s been stolen. I’ve reported ads many times and law enforcement has no appetite to go after them. So long as recycling businesses are allowed to buy them without proof of ownership, the thefts and sales will continue. Local government agencies lock their trucks behind fences with razor wire in an attempt to stop the thefts. The local FDA fleet was victimized a few years back. The thieves took their time and were caught on video.
    I have honestly seen truck beds full of converters going to the scrappers.

    Given the prices of good used trucks lately, I’d consider selling and either renting for occasional use or buying a cheaper, older truck from a pre-cat, pre-electronics, easily-maintained era. If I was to keep that truck, a bolt-on plate under the cat would seem to prevent anyone short on time from stealing it.

    I’ve read that the worst thing you can do is to replace the cat with OEM parts. Aftermarket cats are reputed to have less rare earth material inside and don’t bring the thief as much money. You were wise to move the truck. The thief will be back to steal the replacement in a week or two.

    Both my gen-3 Prius and my 2013 Tacoma have cat shields installed. Just like a door lock, nothing will stop someone who REALLY wants in but experience has indicated that if a cat thief is looking to get in and out in under 2 minutes (the average time it takes to steal a cat) they’re going to move on when they look under my vehicles and see a big-ass plate of thick aluminum covering the whole mess. So far, after two years and a couple of neighbors getting their Prius cats ripped off, I’m happy with the $300 each I spent on this solution.

    The key to stopping this is to go after the buyers. Someone bringing in a cat without a vehicle attached to it has almost certainly stolen it. VINs etched on the part won’t do anything, if they’re stealing them quickly and likely at night, so make it illegal to sell one and you’ll go a long way towards fixing the problem.

    My thought exactly. Just as the people buying appliances , copper wiring , and complete kitchen cabinet sets in ’08,’09 knew they were stolen (if you had a mortgage you didn’t own them) and couldn’t legally sell them. Anyone buying cats regularly knows they don’t just fall off vehicles. Prosecute, severely, the people purchasing them at salvage yards and metal recyclers, and require them to have accurate records with photos of id’s of the sellers.
    Just another example of the low level of integrity and morals in today’s world.

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