P0420, P0300, and P0101

[Chris]

My work van is a 2001 GMC Savana with 180k miles. Two days ago it was running good and yesterday I left for work and it was running poorly.

Within the past few weeks I’ve been getting the P0420 and knew I had to look into that soon (and before my upcoming CA inspection). Yesterday I’m on the freeway with lots of knocking, pinging, sluggishness, I got to work and read the subject codes. Today I am driving my back-up vehicle so the misfiring doesn’t destroy what may be left of my cat.

A few months ago I replaced distributor, wires, plugs (per spec), and the ICM plug/pigtail. Had the P0300 which went away with the first 3 items and then the engine would suddenly stall and would re-start after jiggling the ICM wires. Replacing those fixed that issue. Can’t recall why but I also removed the MAF sensor and cleaned it with the spray (It’s always something with this van).

Had been getting an occasional minor evap system leak code and hadn’t done anything about that.

Do you think that all of these conditions/codes are related or do I have to chase them independently? I wish I could afford to retire this thing but I’ve been nursing it along.

Thanks for your ideas!

Topic

[college man]

[quote=”tractorman” post=167967]My work van is a 2001 GMC Savana with 180k miles. Two days ago it was running good and yesterday I left for work and it was running poorly.

Within the past few weeks I’ve been getting the P0420 and knew I had to look into that soon (and before my upcoming CA inspection). Yesterday I’m on the freeway with lots of knocking, pinging, sluggishness, I got to work and read the subject codes. Today I am driving my back-up vehicle so the misfiring doesn’t destroy what may be left of my cat.

A few months ago I replaced distributor, wires, plugs (per spec), and the ICM plug/pigtail. Had the P0300 which went away with the first 3 items and then the engine would suddenly stall and would re-start after jiggling the ICM wires. Replacing those fixed that issue. Can’t recall why but I also removed the MAF sensor and cleaned it with the spray (It’s always something with this van).

Had been getting an occasional minor evap system leak code and hadn’t done anything about that.

Do you think that all of these conditions/codes are related or do I have to chase them independently? I wish I could afford to retire this thing but I’ve been nursing it along.

Thanks for your ideas![/quote]

The p0420 is your cat is not cleaning to spec.The p0300 could be caused by the p0101 maf sensor.
I would investigate the p0101 first to see if it will take care of the p0300.

http://easyautodiagnostics.com/gm/4.8L-5.3L-6.0L/diagnosing-the-maf-sensor-1

[Will]

P0420 is a catalyst low efficiency Bank 1. Check for an leak or crack in your exhaust pipe. On some cars this is the root cause. It can also be a bad catalytic converter or a faulty O2 sensor.

You may want to try and fix the other problems then see if this is still there.

http://www.p0420.com/

[Chris]

Thanks,
Yes, that confirms what my code reader displayed. I’m planning to check my MAF sensor first as that is easy to do and might be causing the misfiring. There is a small hole in my muffler but of course that is downstream of the post-cat O2 sensor and probably not a factor.

[Will]

Sure, check the MAF out. However, if this error still persists, I would recommend repairing any holes in your exhaust before condemning the cat. Sometimes only a small leak can cause this problem.

I currently have a similar problem (P0430) on my current car. The front y-pipe is cracked downstream of the O2 sensor and it throws the error every so often. I usually just clear the code and it will return in a couple of months or so. All the cars of this make and model have the same problem after a certain number of years. It has been this way for over a year, but I have ordered the part and will install it this week.

[Author]

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