06 silverado v-6

[oomag12]

Local Mechanic welded in new cat. converter and installed upstream sensor..........still had engine light and power loss..... his hand held diagnostic tool then had the same code as before(catalytic efficiantcy bank 2) he than suggested a tune up, wires, plugs, cap, button....same code, loss of power, rotten gas milage. He tells me the downstream sensor is fine, but after the above parts list and labor he's begining to get a little deep in the pocket. This truck was produced at chevy's mexican facility, and I have had several issue's with this truck. It has right at 78000. Just curious if anyone has had simular issue's with v-6's in this model, any info I could pass on to my tech, i would appricate it.

[oomag12]

anybody??

[truckdude239]

replace that down steam sensor catalytic efficiantcy is read by the 02 sensor behind the cats many shops see that code and are like hey i can get him for a cat and o2 sensors. tune up doesn;t need to be done untill 100k i'd replace the rear sensor if it was me. it is the only thing left>

[oomag12]

the error code is #430= catalytic efficiantcy below threshold. If anyone can shed some light, i would appricate it.

[Mykk]

As it's already been stated. Your downstream o2 sensor(s) is reading or thinks it reading to many hydrocarbons. That is either a problem with the downstream O2 senors itself or if your mechanic didn't use GM catalytic converters and the aftermarket cats don't quite have the efficiency of the OE cats.

From your description it sounds like a missfire is the original cause of the problem. May it either be ignition related, fuel related or computer/sensor related we couldn't tell you. Power loss & o2 codes sounds like one or more cylinders isn't igniting the fuel is instead sent right down the exhaust, problem is catalytic converters will get destroyed quickly if raw fuel is run through them. Thats probably why your mechanic suggested a tune up, in case your missfire was ignition related. But missfires can also be caused by poor sensor feedback to the PCM.... your MAF, CPS, CKPS, MAP & o2's all play a critical roll to how your truck runs. And as of lately I've also seen bad gasoline & "the cheapest gas station in town" gasoline will cause excessive missfires & pinging on even stock low compression/ stock ignition timing motors

[oomag12]

Originally Posted by Mykk

As it's already been stated. Your downstream o2 sensor(s) is reading or thinks it reading to many hydrocarbons. That is either a problem with the downstream O2 senors itself or if your mechanic didn't use GM catalytic converters and the aftermarket cats don't quite have the efficiency of the OE cats.

From your description it sounds like a misfire is the original cause of the problem. May it either be ignition related, fuel related or computer/sensor related we couldn't tell you. Power loss & o2 codes sounds like one or more cylinders isn't igniting the fuel is instead sent right down the exhaust, problem is catalytic converters will get destroyed quickly if raw fuel is run through them. Thats probably why your mechanic suggested a tune up, in case your misfire was ignition related. But misfires can also be caused by poor sensor feedback to the PCM.... your MFA, CPS, CKPS, MAP & o2's all play a critical roll to how your truck runs. And as of lately I've also seen bad gasoline & "the cheapest gas station in town" gasoline will cause excessive misfires & pinging on even stock low compression/ stock ignition timing motors

Thanks for the input My. Actually, I really had not had any misfire issue's prior to the cat. converter install,but i met him halfway in the thought that maybe a tune-up could be an issue. He was out on vacation and his shop manager I believe he may have installed a generic cat. converter.

[bwood]

I have been dealing with a similar issue on a 01 Buick. Had a muffler shop replace the cat after something broke loose inside the stock one. About 3 days later the SES light came on with cylinder misfire on #6. Checked everything, all good. I cleared the light and about a week later same thing. This went on for about a month then the "Catalyst Eff Below Threshold" started up (P0420). Now before I went out to get an O2 sensor I put some facts together:

After the cat replacment:
-mileage dropped to 19 from 26
-rich exhaust smell
-rough idle
-random cylinder misfires

I called a favor in a the dealership and they hooked it up. I told them what was going on and he looked at the cat. He said it was not a true cat converter. It was more like a muffler than a cat. The upstream O2 sensor reads an irratic pulse wave and the rear should almost be flat. The cat was flowing so fast the the rear was getting a wavy pulse, and the comp thinks there is an excess air issue. To compensate it richens the fuel mix, thus lower mileage and power. When you buy a GM cat the want the old one as a core, he said that they could not accept the one on the car as it wasn't a real cat. She is saving up for the GM converter, $480+$80 for the core since the muffler shop probably sold the old one and stuck us for the new one.

[Mykk]

right, aftermarket cats are great for complete aftermarket exhaust systems with headers & bigger pipes & loud mufflers.

For an others OE application you need cats from the vehicle manufacturer

I have my cats removed due to a clogged cat from a missfire.... but I also write my own computer tunes and turned off downstream O2 SES codes and turned off COT (Cat Over Temp) the name for when the computer richens the fuel mixture when poor downstream o2 signals are recieved

[67ChevyRedneck]

The truck is an '06?

I think the government requires mfg's to warranty converters to 80 or 100K or something like that. It may be too late to have a GM freebie installed if the original was already taken out...

[Josh]

The mechanic that did the work should have told you the cat was still under warranty for 8yrs/80k miles... Aftermarket cats DO NOT work. He unfortunately voided your factory warranty by replacing the cat... I have to wonder if he even replaced the proper bank cat (should be a shiny new one on the passengers side)... It's about $480 + tax and labor (1.5 hours max) for the y-pipe with both cats at a dealer. Most dealers stock 2-3 of em as it is pretty common failure.

[truckdude239]

any updates on this?

[oomag12]

Well, here's the "new" deal from my mechanic. First, it was a typo on my mileage, i have 87000 k on her as opposed to 78000, dickslexic..lol......so now we have agreed that he will supply the labor and refund $125.00 on the generic cat. i will supply the oe y-pipe at 325.(unless someone can point me in the direction of better price) so that puts the cat replacement at 675.00 including one new upstream sensor. He told me straight up that doesn't believe thats the fix, but I agreed I will call it even, if it isn't the fix its on me. Not sure if had mentioned before, he uses Carquest for his shop parts, i stopped by and asked for the cat. replacement for this truck and the only part listed was the oe y pipe. So thats the update.

[truckdude239]

i wold still replace the downstream sensor if it was me

[oomag12]

Thanks for the input Dude, the mechanic took the downstream sensor from bank#2 switched it over to bank#1 and brought bank#1 over to bank#2 Same code,......cat. eff. below threshold bank#2. So the sensor worked fine on bank#1 and didn't throw a code over there. SO..........I really believe from what I see installed and from what every parts supplier i can talk to tells me should be on the truck, its the wrong converter.

[truckdude239]

okay well that make sense did not know you had done that test. just an fyi normal change interval is 100kmile for most o2 sensors but it sounds like you have this one on lock down

[truckdude239]

anymore updates?

[oomag12]

Originally Posted by truckdude239

anymore updates?

Well, here's the deal. got the OE y pipe and took it over to my mechanic, he installed it, took her to work today, right about 75 miles one way interstate, run like demon......top end power, low end power, no new engine light codes...he's going to refund me 125.00 for the bull**** converter his lead man installed while he was on vacation. So all is well that ends well. I bascialy did end up paying for the labor on a tune-up though, but at least he made it right.

[67ChevyRedneck]

Sweet!

My truck is 9 yrs old with 116K with the factory cat & sensors, they'll last longer than 100K if you're lucky. Fuel mileage is the first sign. I check my mileage often and it's the same as it was 4 years ago.

My biggest fear is that my fuel pump is waaaaaaaaaaaaaay past the "normal" failure age/mileage. If these trucks have a definite weak point, it's crappy fuel pumps... knockin' on wood...

[truckdude239]

glad you got it fixed

[oomag12]

Originally Posted by truckdude239

glad you got it fixed

Dude, I'm still getting sorry gas milage. No new engine codes, just crap milage. I now have 93000 on her and I'm thinking I need to replace the other three sensors. Also i'm told by the service writer at the dealership these models DO NOT HAVE an external fuel filter??? Any input...

[truckdude239]

normal change interval on o2 sensors is 100k far as i know there is a fuel filter on the driver side frame rail. i've yet to see one without on. what kind of plugs and wires did they install? hows the air filter? ont he o2 sensor i would use only gm parts plugs should be platinum plugs