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Discussion Starter · #1 ·
My '13 volt has been an emissions nightmare since I got it with a 100K miles (now @ 197K). When I bought it the car's comprehensive mpg calculated to be 32 and was predominantly ICE driven (10K miles on electric) . Historically, it would get emissions ready after some work; changing oxygen sensors, spark plugs, replaced the Cat with a used one on ebay (that was dumb, I know), seafoam, BG MOA oil treatment, air filter, etc.
But this year, it will not get Cat + oxy sensor ready. OBDII codes present: o2 sensor low voltages, delayed response, 420 catalyst underperforming. The same codes actually with both the original CAT and the used one I bought on ebay. But recently I tried something totally different.

The car always idled bad if the hood was up and running. Sounded a lot like misfires and engine jerks, similar to bad gas. Fine at higher revs with the foot on the pedal idling. Exhaust smell would always find its way into the cabin when stationary and it smelled a little rich. Even if recirculation was on with a charcoal cabin air filter, you always smelled exhaust fumes while stationary. I completely dismantled the intake up the engine block, trying to suffocate the engine to failure at each component to rule out leaks. It wasn't until I got to the throttle body that the engine came close to failure. I took out the intake manifold (very difficult to pull out of the engine compartment), inspected it for damage, and noticed buildup around intake openings on the block. Cleaned the block, replaced the gasket on both the block and between the throttle body and the manifold.

Of note, the intake manifold had traces of engine oil in it and engine oil came out of the exhaust pipe, which I'm guessing was due to the vacuum while pushing the oxygen starved engine to failure. Cleaned carbon buildup off the engine block's intake, used plastic safe spray for the mass airflow and cleaned the injectors with it. The engine smoked for a couple of minutes but has been idling a lot better. Hardly kicks anymore and the mpgs are around 35 - 40 depending on the air temp. But it still will not make the Cat/O2sen ready for emissions testing. I've disconnected the battery, drove it hard in mountain mode on the interstate. The next thing I'm going to try is swapping out the downstream O2 with an used one I replaced earlier to see if it makes a difference.

I have a strange theory that it might an electric problem. When I graph the O2 sensor voltages, both up/downstream, the upstream voltage is strange compared to the downstream. It constantly drops out and jumps back up like there is a problem with the circuit. I've changed the upstream sensor and it's still the same. There is also a high pitch whine through the speakers when power is being generated by the ICE, which has been there since I got it. Needless to say, this has driven me up the wall. Maybe a ground has come off. It had some body work and there may have been a ground that wasn't reattached. I'll have to look through the service manual and see. I was hoping this intake work would be the final fix for my emission woes.

This is scattered logic but any support, direction, suggestions are welcomed. Thank you in advance.

“When we love, we always strive to become better than we are. When we strive to become better than we are, everything around us becomes better too.”
― Paulo Coelho, The Alchemist
 

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Discussion Starter · #2 ·
Can't get emission ready

My '13 volt has been an emissions nightmare since I got it with a 100K miles (now @ 197K). When I bought it the car's comprehensive mpg calculated to be 32 and was predominantly ICE driven (10K miles on electric) . Historically, it would get emissions ready after some work; changing oxygen sensors, spark plugs, replaced the Cat with a used one on ebay (that was dumb, I know), seafoam, BG MOA oil treatment, air filter, etc.
But this year, it will not get Cat + oxy sensor ready. OBDII codes present: o2 sensor low voltages, delayed response, 420 catalyst underperforming. The same codes actually with both the original CAT and the used one I bought on ebay. But recently I tried something totally different.

The car always idled bad if the hood was up and running. Sounded a lot like misfires and engine jerks, similar to bad gas. Fine at higher revs with the foot on the pedal idling. Exhaust smell would always find its way into the cabin when stationary and it smelled a little rich. Even if recirculation was on with a charcoal cabin air filter, you always smelled exhaust fumes while stationary. I completely dismantled the intake up the engine block, trying to suffocate the engine to failure at each component to rule out leaks. It wasn't until I got to the throttle body that the engine came close to failure. I took out the intake manifold (very difficult to pull out of the engine compartment), inspected it for damage, and noticed buildup around intake openings on the block. Cleaned the block, replaced the gasket on both the block and between the throttle body and the manifold.

Of note, the intake manifold had traces of engine oil in it and engine oil came out of the exhaust pipe, which I'm guessing was due to the vacuum while pushing the oxygen starved engine to failure. Cleaned carbon buildup off the engine block's intake, used plastic safe spray for the mass airflow and cleaned the injectors with it. The engine smoked for a couple of minutes but has been idling a lot better. Hardly kicks anymore and the mpgs are around 35 - 40 depending on the air temp. But it still will not make the Cat/O2sen ready for emissions testing. I've disconnected the battery, drove it hard in mountain mode on the interstate. The next thing I'm going to try is swapping out the downstream O2 with an used one I replaced earlier to see if it makes a difference.

I have a strange theory that it might an electric problem. When I graph the O2 sensor voltages, both up/downstream, the upstream voltage is strange compared to the downstream. It constantly drops out and jumps back up like there is a problem with the circuit. I've changed the upstream sensor and it's still the same. There is also a high pitch whine through the speakers when power is being generated by the ICE, which has been there since I got it. Needless to say, this has driven me up the wall. Maybe a ground has come off. It had some body work and there may have been a ground that wasn't reattached. I'll have to look through the service manual and see. I was hoping this intake work would be the final fix for my emission woes.

This is scattered logic but any support, direction, suggestions are welcomed. Thank you in advance.

“When we love, we always strive to become better than we are. When we strive to become better than we are, everything around us becomes better too.”
― Paulo Coelho, The Alchemist
 

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Discussion Starter · #3 ·
I just did a software recall. Updated the HPCM2 hoping it would clear my permanent code "O2 sensor delayed response - lean to rich bank 1 sensor 1". It's still there. I've already replace both up/downstream sensors recently. I requested they clear any and all DTC's. Right now it's 4/8 ready for emission. I was told only driving it would complete the drive cycle.
Strange thing is I had it in mountain mode while parked. The RPMs were almost idle speed, lower than usual. It charge the car up to one bar below half and the engine cut off. First time I've ever seen that. Maybe it's calibrating the battery? I've never spent so much time trying to get a vehicle ready for emissions. If I had the money, I'd sell it for next to nothing and buy a model 3.

Any ideas?
 

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General ICE emissions info:

The pre-cat O2 is for both open and closed loop A/F ratio control.
The post-cat O2 is to check the cat function. These numbers fluctuate wildly. The only number reasonably stable is WOT open-loop operation of the pre-cat sensor. This reading is used for adjusting Fuel Enrichment for racing purposes.

You may or may not be able to find O2 Emulators. These are used by hotrodders to run the engine without a cat and mimic a functioning cat. Do Not Use an emulator for the S1 sensors. Just the S2, post-cat. It plugs into the harness instead of the O2 sensor.

Good luck.
 

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Discussion Starter · #5 ·
Something like this? https://www.plxdevices.com/PLX-Wideband-O2-Air-Fuel-Ratio-Sensor-Modules-Gauges-s/125.htm

Thanks for the reply.

General ICE emissions info:

The pre-cat O2 is for both open and closed loop A/F ratio control.
The post-cat O2 is to check the cat function. These numbers fluctuate wildly. The only number reasonably stable is WOT open-loop operation of the pre-cat sensor. This reading is used for adjusting Fuel Enrichment for racing purposes.

You may or may not be able to find O2 Emulators. These are used by hotrodders to run the engine without a cat and mimic a functioning cat. Do Not Use an emulator for the S1 sensors. Just the S2, post-cat. It plugs into the harness instead of the O2 sensor.

Good luck.
 

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The pre-cat O2 sensor should be fluctuating from approximately 0-1volt, that is normal operation and it should be occurring fairly rapidly. The post-cat O2 sensor should be steadily at the low end of the scale indicating it is lean and the catalytic converter is working as it should. If the post-cat O2 sensor is mimicking the pre-cat O2 sensor then the catalytic converter is bad. If the voltage is actually dropping out on the pre-cat sensor (sensor 1/1) then there is either a wiring issue, ground issue or bad O2 sensor. The monitors will not set if there is a code for that system. You won't get the O2 monitors to set to pass the emissions test if there is an O2 sensor code stored in memory.
 

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No, those are widebands for racing. S1 only. They are not emulators, which are probably illegal by now, but might be found.

https://www.youtube.com/watch?v=qHD7T7EhuzI

These are also known as foolers.

New cars can take over 500 miles of operation to clear the code or record a successful test cycle. Some older cars will clear it in as few as 3 drive cycles.
 

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Discussion Starter · #8 ·
I suspect the cat is bad. The matrix isn’t deformed or discolored from the top. Operating temperatures regularly hit btw 1500 and 1600F. The precat fluctuates between .1 and .8 V and post cat likes to follow it unless it’s idling. Then it just slightly oscillates at .7 V. Regularly smell exhaust and burning rubber in the cabin if I run MM stationary. Even with recirculation on and a cabin filter. The previous O2 sensors had about 60 - 70K miles and were dark without silica deposits. I’d been getting P0420 codes about 10K miles ago and attributed it to changes in temperature and having a POS buggy car.
If I get a new cat from rock auto, it will be the 3rd one I’ve bought for this car. Seems to fail at 100k miles and I’m at 197K.
I really appreciate the feedback you guys are giving me. I’d rather fix the problem then bandaid. I tried torquing down the exhaust manifold to the ICE and stripped the top/driver side bolt. I hope they’re not some kind of exotic metal that can’t be welded because mine are orange. The Cat itself is brown/orange. It’s starting to look like my cat is dead. :(
 

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The only time to buy a used cat is when you can see the junk car. Wrecks with low miles.
 

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Discussion Starter · #11 ·
I took it to a local chevy dealer and their was 8 software updates that they installed. Finally cleared the permanent DTC, now in a holding pattern while the car determines ready status.
 

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I got so excited reading through this thread only to be crushed at the solution being "took it to the dealer to clear the codes." Ugh. I replaced my upstream O2 sensor and have had weird engine issues since then. I have the service manual, and haven't been able to do a specific "HO2S heater resistance learn reset with a scan tool" that it calls for. I have done everything I know to do to reset the ECM but I think only a drive cycle will do that. Initially after the replacement, I turned the car on and it puttered out with an error stating "Engine Not Available" and "Reduced Propulsion Power". I charged it and drove it for a few minutes over 60mph but that was before I knew what the specific drive cycle was (I do now but I'm in CA and the car is in AZ bc I am not sure I can get it home.) If it was on engine mode, it wouldn't drive. I still have two permanent DTCs, despite the fact that it doesn't seem to putter out anymore. They are P015B "O2 Sensor Delayed Response - Lean to Rich (Bank 1 Sensor 1) and P16E0 Engine Performance - No Torque Detected. The P015B was the original code that led me to replace the upstream O2 sensor. The CEL is not on, these are permanent codes that show on my scanner.

So my question is... now that I know the specific GM drive cycle... is that completed when the Volt is on electric power or only with the engine running? It is the same drive cycle that cleared a permanent code on my Jetta after I replaced the Evap Leak Detection Pump, so it is definitely a good cycle (at least for VW it was!)

http://http://www.obdii.com/drivecycle.html

Any thoughts or advice would be greatly appreciated!

Melissa
 
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