GMC Terrain, Equinox, and SRX Forum banner

21 - 27 of 27 Posts

Registered
Joined
4 Posts
Hey there, I have the same code recurring, and a couple of notes that might help figure it out? I don't know the reason, it just comes on while operating normally.

It's a 2014 2.4L with 160,000km (100,000 miles). A couple of othher things happened about the time of the code cropping up.
From cold, the car starts well. If it's shut down for 60 or 90 minutes, it restarts very rough, until the closed-loop systems kick in after 15 seconds. There's a smell of gasoline when this happens. Probably not coincidentally, the resonator needed replacing after exploding, probably from the gas being spit out. Many times the P0420 comes on after this rough start.
If I scan the first O2 sensor it jumps around like you expect. The second is pretty stable.
I don't see any vacuum or exhaust leaks, but the mesh around the flex pipe is broken at the out end.

Does this sound to be a worn cat, or a sensor? Almost seems like a control system problem. Also, is there any warranty for cats on a Canadian car (just asking)?
 

Registered
Joined
538 Posts
Sounds like totally bad injectors, you had a resonator explode? Running a car that long that way I'm not surprised you have bad cats. No special warranty for Canadian cars but I am sure they are very cheap for those cats. Out here in California you cannot even find the special cats required for emission standards which are very high just assuming you have a regular catalytic converter but just smelling gas at the tail pipe when you start it is normal your smelling it because you got that hole in your flex pipe. The exhaust would not be able to explode like that unless if you have an exhaust leak creating tons of oxygen in the exhaust... it could do it again. Hole in exhaust plus excess fuel in exhaust = 馃挘 gas doesn't necessarily kill the cats but the engine running rich would definitely. They are coated in a mixture of metals on the inside that breaks down in extreme temperature from running rich. P0420 does not effect engine performance its just letting you know you have high emissions detected from the downstream sensor.... either your upstream 02 is bad or the injectors could be another sensor like a maf or a temperature sensor. Try fuel injector cleaner these direct injection systems require extra attention you cant just drive it you have to maintain it maybe it will come back.
 

Registered
Joined
1,309 Posts
DTC鈥塒0420
Catalyst System Low Efficiency
Circuit/System Description
A 3-way catalytic converter controls emissions of hydrocarbons, carbon monoxide (CO) and nitrogen oxide (NOx). The catalyst within the converter promotes a chemical reaction, which oxidizes the hydrocarbons and the CO that are present in the exhaust gas. This process converts the hydrocarbons and the CO into water vapor and CO2, and reduces the NOx, by converting the NOx into nitrogen. The catalytic converter also stores oxygen. The engine control module (ECM) monitors this process by using a heated oxygen sensor (HO2S) that is in the exhaust stream after the 3-way catalytic converter. The HO2S 2 produces an output signal that the ECM uses to calculate the oxygen storage capacity of the catalyst. This indicates the ability of the catalyst to convert the exhaust emissions efficiently. The ECM monitors the efficiency of the catalyst by allowing the catalyst to heat, then wait for a stabilization period while the engine is idling. The ECM then adds and removes fuel while monitoring the HO2S 2. When the catalyst is functioning properly, the HO2S 2 response to the extra fuel is slow compared to the response of the HO2S 1, which is located before the 3-way catalytic converter. When the HO2S 2 response is near that of the HO2S 1, the oxygen storage capability and efficiency of the catalyst may be degraded below an acceptable
 

Registered
Joined
4 Posts
Could be injectors like you say. It idles rough when it's open-loop, then smooth when it goes closed-loop. That's only after 90 minutes of being shut down, it's smooth at cold or hot (short shutdown) start. I put some cleaner/cat cleaner but it'll take some time to run through.
BTW here is the flex pipe that's broken, camera is facing engine.
17632


Here are scans after driving for a while of O2 sensor2 1 and 2, at idle, then 2000RPM

Here are scans of those sensors at 2000RPM

Maybe the cat is not working.
 

Registered
Joined
4 Posts
Resonator didn't explode really it was split at the seam and wide open. I had a car that flooded, it wouldn't start, sent so much gas into the muffler that it eventually did explode, but it looked like the resonator too.
 

Registered
Joined
538 Posts
Dang well does the downstream 02 sensor ever settle down like at a steady voltage? Based on your data it looks to me like your actually pumping lean air into the exhaust out of one of the cylinders not rich the top video around the 40 second mark you can really see it when the voltage dips down to .220 umm that would mean the car is like a lot of oxygen or running really lean
 

Registered
Joined
4 Posts
40s is when I raised RPM from idle to 2000. The suggestion of an injector might be the culprit, which could cause the rough open-loop idle.
Took the intake hose off and whoo what an oil smell. This can't be good.
Some time back I had the cam phasers recall done I wonder if the intake one might need replacing.
 
21 - 27 of 27 Posts
Top