Code P2432, Secondary Air Injection

[b.miller123]

Finally got around to pulling the code related to this post: P2432 Secondary Air Injection System Air Flow/Pressure Sensor Circuit Low

Seems like this isn't exactly a common issue. Doing a quick search, about the only thing I could find on the net was a link to these pages in the FSM: http://4runnerclub.com/i/4r_files/f...7toyrm/07toypdf/07rmsour/4runnerr/0060065.pdf

Of course, to check the sensor, step 1 is to remove the intake manifold :banana: Time to dig through the FSM and see exactly where this stupid sensor is, and hope I find something obvious like a broken wire. Of course this happens now when I need to get emissions done this month. Hopefully I can bypass the sensor or something. According to the link above, it needs to send between 0.1v and 4.8v....

I did see this recent thread: http://www.toyota-4runner.org/problems-warranty-issues/66938-air-injection-system.html but I am not sure if my problem is related. I've seen a couple other posts similar to that one, but nothing about code 2432 specifically.

 

[b.miller123]

Well after looking into it, the sensor is part of the valve. Well at least I can't find the sensor anywhere by itself. I think I am going to bypass the sensor at the ecu and give it an artificial 2.5v from somewhere. I'm not 100% sure what the logic of the ECU is with this input and if it needs it to vary, but 2.5 is right in the middle of what the sensor gets from the ECU.

Normally I wouldn't bother trying something like this, but since the damn plug to the sensor is under the intake manifold, I can't even troubleshoot the issue to see if it is the wiring, the sensor/valve or the ECU without yanking off the manifold and possibly wasting a weekend.

And today I've discovered a headlight wire is damaged. Seems like the crap is never ending with this thing.

 

[b.miller123]

Okay, after looking into the system some more, and reading a huge thread on the bypass over on tundra solutions, I've found what I think will trick the ECU into thinking the sensor is on.

The bypass will only trick the ecu into not turning the AIP system on when the engine is starting. My codes are being generated before the engine is even running. So this tells me that the ECU is checking the pressure sensor as soon as the ignition is turned on, before engine start. It would be easy enough trick the ecu before the start, but after, when the pump is actually working, the pressure sensor would possibly be sending the wrong signal.

Looking at page three of the pdf in this post (also attached), the ECU checks the pressure sensor to see if the pressure matches the logic of the pump and vsv actuation. If I do the bypass, the ecu will always be thinking the pump is off and vsv's are closed, and that pressure matches that logic. The diagram shows the pressure should be "zero", but I don't know if they mean one standard atmosphere, or actually zero. I would assume that they mean 1 atm.

Since 1atm = 101kPa, according to their chart, (with 45kPa=0.5v, and 150kPa=4.5v), I need about 2.63v from the sensor. The input voltage is 5v, so I'll cut that in half to 2.5v with a voltage divider. Hopefully the 0.13 difference won't be enough to make a difference in how the ECU reacts. Basically I'll just place a resistor two resistors in the circuit. One will be between the 5v input source and the output to the ecu, and the other between the output and ground. This translates to one between the white/light blue and the light blue/red, and one between the white/light blue and brown (Page three of the attached 70-83 PDF). As long as the resistor values are the same, the voltage will be cut in half, and the ecu will get 2.5v back (probably a little less). So it will think the pump isn't on. This is fine, as long as the ECU doesn't think the pump should be on, hence the need to do the bypass. While I'd love to do the plug and play bypass, I think the relay/resistor one will work just fine for about 1/20th the cost.

 

[b.miller123]

Well after messing around with it some this weekend, it appears to be fixed.

The first shot was placing two equal resistors in the system. One (R1) between the sensor input (blue/red wire) and output (white/blue wire), and one (R2) between the sensor output (white/blue wire) and ground (brown). The resistors were 4.7kOhm for both, which should have led to a 0.5 multiplier of the 5volt sensor input, but I still wound up with around 4.3v while the engine was off (pump not running), and 4.8v on startup (pump running). Obviously not what I wanted, and not within range. I think the reason for the higher output voltage was due to the existing resistance between the output and ground.

This also threw the following code after engine startup: P2431 Secondary Air Injection System Air Flow/Pressure Sensor Circuit Range / Performance Bank1. When doing a test drive, the limp mode was on, and strangely it was actually worse. Seems like there must be two different limp modes because the previous one with code P2432 at least allowed me to get up to freeway speed, albeit a little slowly. No way I was getting over maybe 40mph in this mode. Got home, checked the codes again and had the infamous P2440 code for a stuck valve. I was expecting this anyways since the ECU isn't getting what it thinks it should from the pressure sensor. Unlike my first code P2432, where it knew the sensor wasn't working, this time it thought it was, but it was just out of the expected range. I think this is the reason for the worse limp mode.

So after some thinking it over and doing some rough calculations, we decided to just throw another 4.7kOhm resistor in series with the resistor between the output and the input and see what happened. This put the R1 value at 9.4kOhms (it was actually lower, they measured at about 4.62). So the voltage divider would theoretically output 1.66 v to the ECU (not counting the existing resistance from output to ground). After installing it, it came in at about 2.3v. We cleared the codes and took it for another test drive. This time I was expecting and got no codes related to the sensor. I was actually expecting a code for the valves, but never got one. I think for now it is problem solved, but I guess we will see...

I think I will still disable the AIP system anyways, just to keep it from causing any further issues. Hopefully I won't have any more issues with this stupid sensor. If it decides to suddenly work again, I'll probably have issues again. I'll just have to come up with something more permanent the next time I am doing some major engine work.

 

[b.miller123]

I guess I might as well update this. Everything was fine for a while with the cold weather, but then after it warmed up a bit, the system tried to turn on and a code popped for either a valve stuck open or pump stuck on. This was expected, so I just bypassed the system.

Everything went well for a little while until last week when a code popped up for the bank 2 knock sensor. Took a better look around the engine bay and it seems like I have a critter of some kind living in there... So hopefully faith will be restored in Toyota if this all winds up being due to a rodent chewing on wires.