P0402 code

I have a 2001 Tacoma PreRunner 3.4L 6 cycl engine. Do you think it is the EGR valve that needs replaced? I have read some threads of the 2.7L engine but none on the 3.4L but none on my engine. Truck runs great, the check engine light just keeps coming on after it is cleared. Thanks!

 

I thought the 3.4L V6 didn't have an EGR?

 

Is it possible you transposed 2 digits?
Maybe you have a P0420.

 

Doesn't P0402 point to a possible exhaust leak, O2 sensor defect, or catalyst problem?

 

Rick, you may be right, I may have written it down wrong. So how do I correct the P0402 code?

 

It has to do with the catalytic converters mine throws the same code cause I removed them, so I'm sure yours need to be replaced or something

 

Assuming you have a P0420 (not P0402) the problem is related to the converter.

You either have an exhaust leak, bad sensor or bad converter. There should be 2 sensors, before and after the converter.

Visually check for exhaust leak. If there is one, there would likely be black soot in that area.

If that is OK, then check the sensors. You can do this by disconnecting the wiring plug from each one, and measuring to see if the resistance is in the correct range for each one (you'll need the FSM to locate the proper terminals). If not in range, replace that sensor.

The sensor can be bad, even if the resistance check passes, but you need a special tools to verify it. The post-converter sensor is heated, so its remotely possible that the ECM is not sending power due to broken wire.

If they both check out, then likely the converter needs to be replaced.

No experience here, just reading this stuff from the 2003 FSM for 3.4 motor.

 

My wife's 2001 Tacoma 2.7l 4x4 has been throwing that P0420 code every few days for several months. When it first started I went under the truck and checked for leaks, but none found other than a pinhole after the last o2 sensor where the pipe was welded to the inlet of the muffler. Since that was after the O2 sensor and the truck has almost 100k I figured one of the catalytic converters was bad. About a week ago while I was driving the exhaust got really loud after I drove it hard. Turns out the bolts for the last O2 sensor had rusted or fallen out and the sensor came out. It must have been a little loose all those months. I cleaned out the thread, installed a new gasket and the check engine light hasn't come back in over two weeks now. Simple fix and didn't cost a thing to repair.

 

Had the same code issue. Life long friend and mechanic said it was the cats. Would not mess with the running of the truck just have to look at the light. After a few months this drove me nuts. Had another Diag. replaced both cats and all is well. Truck ran fine the entire time 20mpg in town driving. O2 sensors tested out fine. Would have rather bought new wheels tho.