I have a 2002 Tacoma 4x4, 4 cyl, 2.7l. Truck has 175,000 miles.
Recently, both O2 sensors were replaced due to engline light/codes that led to a check where both sensors were diagnosed as bad. I regret that I allowed a local shop to do that work (just because my laziness costs me quite a bit more $). But problems persists, so I'm working to resolve.
Soon after (same day) they replaced the O2 sensors, engine light came back on. Rather than return to the shop, I've decided to try and resolve on my own. So I checked code: P0420 (Cat System Efficiency Below Threshold).
Long shot as it may be, I decided I'd pull both cats and try to clean them. I soaked them overnight in a mild dish detergent/water solution. While they soaked, I renewed air cleaner and put in fresh plugs. After re-install, I cleared the codes. After about 175 miles, engine light came back on. Codes now are as follows:
Freeze Frame: P0420 (Cat System)
Pending: P0401 (EGR) and P0420 (Cat System)
I'd appreciate insights and opinions here. On the P0420, I suppose it's likely that the Cat may well be near end of life given the mileage, so I was inclined to replace the front cat to see if that would be enough, then replace the rear only if that didn't resolve the P0420.
As for the P0401, could it be related, or is this definitely a separate issue with the VSV or some such?
I have about 3 weeks to get it resolved (inspection due so need to resolve for emissions check).
Thanks so much in advanced for advice or help.