gray420

I have a 2000 4Runner 3.4 auto. A few months ago the CEL came on, so I had it checked out and was told the code said to replace the AF sensor. I ordered one from URD and put it in. CEL went off and stayed off for two days. I just got the codes read again, and this time it's
P0335 - Crank pos sensor
P0340 - Cam pos sensor
P0420 - Bank 1 catalyst...o2 sensor

Also, the truck has an intermittent problem starting where it will click a few times then engage and start fine. Occasionally it will hard start and die, then start up and idle fine. Mileage is worse than before I changed out the AF sensor. Are the codes that Advanced pulled the right ones? In my experience the aftermarket sensors don't work well, is there anywhere to get this other than the dealership? I searched for these codes and came up with little other than for the O2 sensor. Any ideas?

mt_goat

Any extra noise or vibration up front of the engine? When was the timing belt last changed?

I'd focus on the P0335 and P0340 first, fixing those may that care of the P0420.

http://www.ncttora.com/fsm/1996/SIL/...fe/cip0335.pdf

http://www.ncttora.com/fsm/1996/SIL/...fe/cip0340.pdf

gray420

No extra noise or vibration from the front, just a grainy feel to the gas pedal sometimes. I bought the truck at 124k and it's got 148k now. I don't know about the service history or when the t-belt was changed. It's on the list. I went and got a crank pos sensor from the dealership, it was the same price as advanced auto. I have to order the other sensor, not in stock.

mt_goat

I'm not convinced both of those sensors went bad. They are not really a common problem with this engine. Did both of these codes come on at the same time? I wonder if a badly worn timing belt could cause those codes, I didn't see that as a trouble area with the codes....but ...my gut tells me its possible.

gray420

Not sure about the timing belt. Is there any way to tell without tearing everything apart. The CEL has been on for a few months and I just got the codes today, but it seems strange that they came on after the AF sensor change. The weird starting thing is another thing that makes me think the sensor needs to be changed. If I understand correctly, a faulty sensor may cause starter issues. Would a worn timing belt do the same? maybe starter is going too?

Anyways, did a quick search and found Partsgeek had both sensors overnighted for $180 which saves $65 over the dealership. Leaving for DC on thursday and I would like this sorted by then. I guess if the new sensors don't do the trick I can return them and just eat the shipping cost.

mt_goat

Well I did find one guy that replacing the cam sensor fixed his problem: https://www.yotatech.com/forums/f2/c...-sensor-80550/

mt_goat

This is an interesting thread with the same problem: https://www.yotatech.com/forums/f2/s...oblems-128181/