Da old truck was bought in 2003 second handed. With 279k miles of today, truck has been with family since son was a little boy.
The truck has been on and off with the "p0420" code for quite some years. The first time I recall was the cross-country trip in 2012 when we drove the thing for 8k miles in two weeks.
After son took over the truck in 2016, he reported check engine light on (CEL). I have replaced the valve gasket, MAF, and many unrelated parts (key lockers, bumpers, broken light housing). The light went off after he took the car to fix the brakes this past April.
When I got the truck back last month, I did oil change, and reset the battery. The next day I took the truck for SMOG check, which was past due two months (I paid the DMV due on time so to avoid fine). SMOG test failed to my surprise as it's my first time in more than 2 decades. It was hard to understand the failure was due to systems not ready. I was advised to fix a rubber connector before the throttle, and to drive to Davis to reset the truck so it's ready for testing. I ordered the intake rubber tube, when I took it out, I was appaulled to see how brittle the rubber has become after 18 years of service. See picture of the wide open crack (after I checked and poked around so the crack was more likely due to my taking out and squeezing on it), perhaps this is the cause of CEL p0420 code.
Getting the truck ready was intriguing to say the least. There are instructions where steps vary widely. The last I followed was from "carfromJapan", 1) keeping gas tank half full, leaving car over night and start first thing in the morning, 2) let engine run for 2 and half minute with AC and defrost on, 3) drive 55 MPH for a few minutes, stop w/o braking, 4) stop the car and let engine run idling, 5) drive 75 mph for a few minutes, then you are ready for SMOG. Gee, I later learned not to turn on Cruise control, not to keep AC on... I drove to a SMOG station near me and was told again the truck was incomplete on Catalyst, but emission was ready
I took out the catalytic converter, the truck has two pieces, there lied the O2 sensors, both were replaced within the past several years, OEM part as well. To my surprise, the upstream sensor plug one was loose, such that no force was applied to remove it. Could this cause the CEL? Taking off the upstream CAT section was a bit tough. I read enough posts and discussions so mentally I was ready to do some damage. I used the torch to heat up the thread (2000 f? not sure, but the thing turned to red rod during heating) , applying enough w40, which smoked. The screw gave in. and there came off the CAT. To my surprise, how clean is the CAT. I used flashlight to see thr the cone and saw a few tiny burned spot where holes were blocked, but that's it of an 18 yr old Toyota 4runner, clean, not much soot / carbon deposit. I soaked itwith a solution "Purple Power” that has worked marvelously to my FORD truck EGR cooler. The next morning when I poured out the solution, only finding slight darkened color, indicating little carbon deposit.
Debating at least replacing the gaskets, I said to myself, "what the heck, just put it back to see if the code would go away". Satuday morning the truck was on the road again.
Not recall what happened that morning and why LP was so outragous that I'd rather to be homeless. I drove onto I580, and then came the CEL, and two other lights that are more related to an open gas lid. Plugged in the scan tool and there came the infamous P0420 code, showing twice.
That night I slept in the truck, feeling more relaxed of my full extended legs. By 2:30 pm, I sneaked back home and found LP has gone to work. I went ahead and determied to do the 5$ fix to the P0420 code. I did once years ago to the Jaguar after months of work and testing to no success, until I followed someone's posting to add a little extension to the O2 sensor. I passed SMOG test the second day, and I have droven the Jaguar probably 30K miles since then, that code never comes back. Tell me about it, Da $5 fix.
It was funny, the anti-foul spark plug set I bought several years ago was sitting there on the shelf and I have no trouble locating it. Dry fit onto the 4runner hole and it snugs. Quickly I got my Dewalt drill, and the ½ inch metal drill bit, bought for the sole purpose of the P0420 fix. Use a vise grip to hold tight, left foot stepped tight on, there was a less than 1 minute drill so the tip of the sensor would go in.
I kept driving for a few days, no CEL on.
I drove to the SMOG station today morning, it passed.
It made my day.
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