HELP. GX seems totaled bc of bad Cats. (1 Viewer)

[bmathews415]

I just got off the phone with my mechanic who is suggesting that my GX is totaled.

Last weekend my motor died and I spent six hours on the side of the freeway waiting for a tow due to a bad alternator. I replaced the alternator to the tune of about $1200, and almost immediately after picking up the car from the shop, the check engine light comes on. This coded for catalytic converter and I just heard from the tech that all four are shot. He quoted 15 hours of labor alone which puts it north of $4500.



I'm praying you guys can give me some insight into how I may be able to salvage this vehicle. I have thousands in it and the idea of sending it to the GX farm in the sky at this point is making me nauseated. Will a bypass help get the code to go away and I can just live with bad cats? Anything I can do for a reasonable cost to address this issue? Thanks in advance.

 

[Rednexus]

While the cats can go bad, there are lots of other things that can be checked first. Things like replacing the O2 sensors (upstream and downstream), checking for exhaust leaks, etc. Also, the rear cats are behind the O2 sensors, so there is no way a malfunction of the rear cats can trip a sensor-related code. Saying "all four are bad" is a bit of a red flag.

I'd suggest getting a second opinion from a different mechanic who can do some diagnostics before jumping to cats. You can by O2 spacers that will fool the downstream sensors (assuming the cats aren't clogged, in which case they do need to be replaced), however it's unlikely you'll find any mechanic willing to install them as they cannot legally be installed on a highway vehicle. You'd need to source and DIY the install.

 

[bmathews415]

While the cats can go bad, there are lots of other things that can be checked first. Things like replacing the O2 sensors (upstream and downstream), checking for exhaust leaks, etc. Also, the rear cats are behind the O2 sensors, so there is no way a malfunction of the rear cats can trip a sensor-related code. Saying "all four are bad" is a bit of a red flag.

I'd suggest getting a second opinion from a different mechanic who can do some diagnostics before jumping to cats. You can by O2 spacers that will fool the downstream sensors (assuming the cats aren't clogged, in which case they do need to be replaced), however it's unlikely you'll find any mechanic willing to install them as they cannot legally be installed on a highway vehicle. You'd need to source and DIY the install.

Thank you. This jives with what I've been researching. The "tech" more or less the guy on the phone at this shop said pretty definitively that all four cats were shot. I've since learned, as you pointed out that the two cats downstream of the sensors are not monitored by the ECU and thus they couldn't be determined to be bad without physically inspecting them.

So it's either true that the cats are bad, or instead an exhaust leak in the system, or bad sensors. In any case this shop doesn't seem to want to fix it, so I'm thinking if the CEL returns I go to a muffler shop and have the cats cut out, and add some spacers to the 02 sensors to keep the CEL at bay.

Not necessarily ideal but I'm not junking my truck over some emissions codes. I'll find a way to keep the old girl on the road.

 

[Rednexus]

A couple of things:

1. O2 sensors are fairly cheap/easy to replace. Get Denso direct-fit for the upstream and universals for the downstream (universals are maybe $50 per side). I'd suggest relacing them on any GX that has over 125K on it.
2. (Assumes this is not a O2 sensor issue) You may or may not find a shop willing to cut off the cats due to the regulatory issues and fine potential (same thing as the O2 spacers). Also I'm not sure you could really cut out the upstream cats and weld in new pipe without removing the whole exhaust manifold (which is $$$ for labor) with how constricted things are. If they are bad but not clogged, I'd find a way to have the spacers installed. If they are clogged, you're stuck with either getting new exhaust manifolds (which have integrated cats) or a set of long-tube headers which are effectively a cat delete. I have the latter and highly recommend them, but you'd be in around $2K or more for the headers and install labor, minus the ~$600 you could get from selling the old cats.

 

[bmathews415]

Thanks man. I was actually just reading a post of yours describing your long tube header and o2 sensor spoofer device. Even with the cost of that solution, it's significantly cheaper than what I'm being quoted for OEM(?) replacements from these shops I'm taking to ($3.5-4.5k)