CEL Codes....what to do...
06-06-11, 08:07 PM
#46
That is a good sign. That means that the computer already went through a driver cycle and didn't detect the problem that's why theres nothing in the pending codes. I would take a good guess that you probably forgot to tighten your gas cap. Using 87 instead of 91, from my highest opinion would not turn on the MIL. Our PCM are very sophisticated, it's smart enough to compensate for the loss in power and would adjust ignition timing accordingly and still maintain the car's efficiency. Yes, you will lose power but it won't misfire.
06-08-11, 08:07 PM
#47
well it came back again.....its gone again though. love my shop though,i get to go use their scanners (autoboss V-30 scanner) for free and get alot of help if i need . its cleared now so we'll see if it comes back again i may actually work on it FINALLY. same code i got in post # 21
06-09-11, 08:57 PM
#48
Instructor
Hey dude, I'm sure you remember me, I think I can help you out. Forgive for not reading the whole thread, but I too have the 430, and just fixed a p0430, p0440, p0441, p0446. I am used to be a Toyota tech, and now I work at an import shop.
Does that diagnostic thing capture live data, as opposed to just codes? If so, you need to monitor the bank 2, (pass side) o2 sensors, For a while I had an intermittent light, so I couldn't capture it for the longest, finally I got tired of looking at the CEL.
Here is something to kinda think about. The computer has no logic, it literally only knows what it's sensors are telling them. If the sensor is giving a bad reading, like in my case, the ECU doesn't know what's good or bad if it's giving a reading in between normal ranges. This is where the code comes into play, usually the cats don't fail, more often the sensors do. In my case, the sensor was providing a constant .38 volt signal to the ECU. Now, normally this is within the operating range of a working sensor, but because it stayed at .38 volts, the ECU assumed it was getting a good, reliable signal from the o2, and from what it sees (not the cat). So if you were to be playing the ECU, you would look at the front sensor, watch it go up, and then down, and back up, which is what a normal o2 sensor does. Than you would be simultaneously looking at the rear sensor to mimic that high low, but in a narrower range because of the work of the cat-converter. If, the sensor is saying I only see, .38v, the ECU can only logically assume the cat is the problem since the sensor checks out. Make sense?
p0340...
1. Check underneath the car for carbon build up around the flanges after the cat, before the sensor. If you have a slight black build up, it's due to exhaust leaking out, or oxygen getting in causing erroneous readings. Here's mine.
2. With a proper graphing scan tool, because no matter how mathematically inclined you are, you won't be able to crunch the numbers of both sensors going from high to low. So, if you can, graph both the Bank 2 sensor 1 (or B2S1 in the scan tool) o2 sensor, the front one, and B2S2, which is the rear sensor. In my case, the rear out sensor was pegged at .38 volts, not fluctuating at all, just a straight line across the screen.
The fix, was to replaced the B1S2, or driver's rear sensor and the gasket right before the sensor, post-cat.
p0440, p0441, p0446.... Are generic codes for an EVAP problem. They usually all come as a package, and doesn't mean there's 3 separate issues. The evap system is actually pretty easy, and I will try to explain it in easy terms.
The Evap system is like you sucking on a straw, and capping the other end with your finger. If the straw has a crack in it, you won't be able to hold the vacuum you built up from sucking on it. Your mouth acts as the purge valve, which pulls a vacuum on the entire fuel system, charcoal canister, lines, etc., The vent valve would be your finger, which closes the entire system to atmosphere pressure. The most likely cause for EVAP codes are bad purge valve, worn/loose/bad hoses, charcoal canister, or vent valve. The good news is that Toyota combines the charcoal canister and vent valve in one, the bad news is that it's like $300 from Toyota, last time I checked. The purge valve is underneath the Lexus engine cover, and is supplied engine vacuum from the top of the TB to the purge valve, thus the vacuum, and the other side of the valve goes to the charcoal canister/EVAP system.
The ECU supplies the vent valve with a signal to close, so the fuel system is closed to the atmosphere, in order to test the EVAP system. With your finger in place on the straw, you can suck on the straw, so the ECU than supplies the purge valve to open the EVAP system to vacuum from the intake manifold/throttle body. Once the ECU sees a drop in pressure, it will than close the purge valve, while keeping the vent valve closed. At this point, everything that is fuel related is under a vacuum, if there is a leak in the tank, filler neck, fuel cap, hose, charcoal canister, the vent valve won't close, or the purge valve won't open, it will cause the pressure to likely raise again, throwing a code. Make sense?
In my case, I came across a few postings where people had posted that worn motor mounts has caused an EVAP hose to pull off. I don't think mine are worn, but I found this. You have to removed the engine cover, but in the picture you can see the hose pulled off from the EVAP line. This line is coming from the purge valve, so the system had been open to atmosphere, and when it tried to run through its' checks, it wasn't able to build a vacuum obviously.
In this picture you can see the purge valve in the left of the picture, and leads to the charcoal canister, which is underneath the trunk area.
Wow, that was like going back to tech school... Hope this helps, good luck.
Does that diagnostic thing capture live data, as opposed to just codes? If so, you need to monitor the bank 2, (pass side) o2 sensors, For a while I had an intermittent light, so I couldn't capture it for the longest, finally I got tired of looking at the CEL.
Here is something to kinda think about. The computer has no logic, it literally only knows what it's sensors are telling them. If the sensor is giving a bad reading, like in my case, the ECU doesn't know what's good or bad if it's giving a reading in between normal ranges. This is where the code comes into play, usually the cats don't fail, more often the sensors do. In my case, the sensor was providing a constant .38 volt signal to the ECU. Now, normally this is within the operating range of a working sensor, but because it stayed at .38 volts, the ECU assumed it was getting a good, reliable signal from the o2, and from what it sees (not the cat). So if you were to be playing the ECU, you would look at the front sensor, watch it go up, and then down, and back up, which is what a normal o2 sensor does. Than you would be simultaneously looking at the rear sensor to mimic that high low, but in a narrower range because of the work of the cat-converter. If, the sensor is saying I only see, .38v, the ECU can only logically assume the cat is the problem since the sensor checks out. Make sense?
p0340...
1. Check underneath the car for carbon build up around the flanges after the cat, before the sensor. If you have a slight black build up, it's due to exhaust leaking out, or oxygen getting in causing erroneous readings. Here's mine.
2. With a proper graphing scan tool, because no matter how mathematically inclined you are, you won't be able to crunch the numbers of both sensors going from high to low. So, if you can, graph both the Bank 2 sensor 1 (or B2S1 in the scan tool) o2 sensor, the front one, and B2S2, which is the rear sensor. In my case, the rear out sensor was pegged at .38 volts, not fluctuating at all, just a straight line across the screen.
The fix, was to replaced the B1S2, or driver's rear sensor and the gasket right before the sensor, post-cat.
p0440, p0441, p0446.... Are generic codes for an EVAP problem. They usually all come as a package, and doesn't mean there's 3 separate issues. The evap system is actually pretty easy, and I will try to explain it in easy terms.
The Evap system is like you sucking on a straw, and capping the other end with your finger. If the straw has a crack in it, you won't be able to hold the vacuum you built up from sucking on it. Your mouth acts as the purge valve, which pulls a vacuum on the entire fuel system, charcoal canister, lines, etc., The vent valve would be your finger, which closes the entire system to atmosphere pressure. The most likely cause for EVAP codes are bad purge valve, worn/loose/bad hoses, charcoal canister, or vent valve. The good news is that Toyota combines the charcoal canister and vent valve in one, the bad news is that it's like $300 from Toyota, last time I checked. The purge valve is underneath the Lexus engine cover, and is supplied engine vacuum from the top of the TB to the purge valve, thus the vacuum, and the other side of the valve goes to the charcoal canister/EVAP system.
The ECU supplies the vent valve with a signal to close, so the fuel system is closed to the atmosphere, in order to test the EVAP system. With your finger in place on the straw, you can suck on the straw, so the ECU than supplies the purge valve to open the EVAP system to vacuum from the intake manifold/throttle body. Once the ECU sees a drop in pressure, it will than close the purge valve, while keeping the vent valve closed. At this point, everything that is fuel related is under a vacuum, if there is a leak in the tank, filler neck, fuel cap, hose, charcoal canister, the vent valve won't close, or the purge valve won't open, it will cause the pressure to likely raise again, throwing a code. Make sense?
In my case, I came across a few postings where people had posted that worn motor mounts has caused an EVAP hose to pull off. I don't think mine are worn, but I found this. You have to removed the engine cover, but in the picture you can see the hose pulled off from the EVAP line. This line is coming from the purge valve, so the system had been open to atmosphere, and when it tried to run through its' checks, it wasn't able to build a vacuum obviously.
In this picture you can see the purge valve in the left of the picture, and leads to the charcoal canister, which is underneath the trunk area.
Wow, that was like going back to tech school... Hope this helps, good luck.
Last edited by 3UZFTE; 06-09-11 at 09:00 PM.
06-10-11, 01:13 AM
#49
Brian, bank 2 is on the passenger side. Check for exhaust leaks. Since you got a dandy scanner there, go to Live Data (Parameters) and check the B2S2 oxygen sensor reading. The reading should be a bias rich reading, like a .8 mV. If you are getting a fluxuation reading, that sensor is triggering wrong signal. Must be changed.
06-10-11, 05:22 AM
#50
Instructor
Brian, bank 2 is on the passenger side. Check for exhaust leaks. Since you got a dandy scanner there, go to Live Data (Parameters) and check the B2S2 oxygen sensor reading. The reading should be a bias rich reading, like a .8 mV. If you are getting a fluxuation reading, that sensor is triggering wrong signal. Must be changed.
Sakataj, What are your short and long fuel trims?
06-11-11, 07:56 AM
#52
3UZFTE ty, i will look at the flanges next time its on the rack....as far as the purge line coming loose, wouldnt this cause a instant CEL light? mine comes and goes.... stayed away last time for almost 4 months.
john, i dunno if that scanner reads live data its at their shop so i dont have access to it always....i can ask him next time i go and get the readon on the O2 sensor
john, i dunno if that scanner reads live data its at their shop so i dont have access to it always....i can ask him next time i go and get the readon on the O2 sensor
12-28-11, 10:55 AM
#57
no john i didnt....for 2 reasons, one i was being lazy cause i cleared the codes and havent seen it since....just like this one. i cleared it the day i posted it and havent seen it again since (knock on wood) and two cause i meant to address this when i installed my headers which i STILL havent done so i just havent looked into it
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