Den20

Secondary air system problem

12 posts in this topic

Hi everyone, I'm a new member. 

 I've been searching all the forums for a solution to my problem to no avail, so I thought I should ask - someone else must have come accross this.

 

The cars 2008 legacy. The secondary air system has'nt worked for ages but its all still there except I unplugged the air pump. Originally I could clear all the codes, and they wouldnt come back for a few days, but after a while p2433 wouldn't clear. (Thats pressure sensor high). I was thinking the sensor might be defective but now I've looked in to it I have found the signal wire aways has 5v on it, even when disconnected from the sensor. So its not due to a sensor fault. Im pretty sure its not a short circuit to the 5v power supply wire (145k ohm resistance between wires) Its got to be comming back from the ecu and I guess the question I have is how to fix that?

 

It would be good to get rid of the check engine light and have the car fully functional again.

Thanks. Any help is appreciated.

Den20

 

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Have you pulled the air pump fuse?

 

Been a while and not sure if it’s exactly where you are but think there’s a pull up resistor in the ECU for that. Vaguely remember a few people trying to reallocate some of the unused wires/pins in the ECU after doing the delete in the software to connect to a wideband or something like that and running into issues as it always read 5v regardless of what they did.

 

Other thing to do is get someone with a Tactrix cable to disable that code entirely, then it’ll never come back.

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Thanks for your reply Andy. I pulled the air pump fuse but it will be a few days before I can look at the ecu. Is a pull up resistor one that can be unplugged or something?

We have tried to get some one to delete the codes but they apparently werent able to delete that particular one because it was an active fault. I suspect they might have actually deleted all the other sec air system codes because they no longer come up.

Ill let you know how I get on withe the ecu.

Cheers

 

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So if you reset the ecu then turn the ignition back on but engine not does the code come straight back?

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Yes thats right. I can clear it and check engine light goes out but its back in about 10 seconds. The fault comes up just with the igniton on as well as when the motor is running.

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So when you say delete, do you mean they just wipe the history of it? Not sure if whatever they’re actually is a permanent fix. 

 

What you need to do is to pull the ROM from the ECU with ECUFlash/ROMRaider disable that code there then flash the altered ROM back to the ECU. That’s probably the only way to stop it coming back for good. 

 

That doesn’t mean it’s mechanically the right thing to do though. 

 

What part of the country are you in?

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By delete I do mean disable.

 

 I live in Ohakune and we (my wifes car) took it to Ellite motors in palmerston north about a year ago and they said they couldnt disable that fault "code" it while it was active. I dont think they were considering re flashing the ecu. I agree thats probably the way to go. Can you recommend anyone or know of anyone central north island who could do that?

 

I would still like to know why it has a high signal even when disconnected. That seems to me like  an ecu fault. My intention when i thought the pressure sensor was faulty was to disconnect it and use resistors to fudge a mid range signal eg 2.5v. 

 

Do you know if the sensor does anything other than proving tbe secondary air system is working correctly.  Most people when they disable this system seem to retain pressure sensor for some reason.

 

Thanks for your help with this.

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What kind of timeframe were you considering for resolving it? Not sure who’s down that way besides @Joker who tends to only play around with cars almost older than me. He might have an insight into some clued up members/shops in that area

I’m somewhat down those ways every month so could sort it on the way through, only takes 10-20mins if things go to plan.

 

How mechanically inclined are you? For the amount of time required to fudge around with it to keep it in place, buying the blockoff plates and deleting the lot isn’t actually that much worse. Means there won’t be any valves open bleeding air/exhaust gases through when not running.

 

You need to retain the atmo sensor which is in the drivers side solenoid as the ECU uses that so without it it never knows if you’re above sea level or not.

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We've lived with this for over 2 years and the only issue is its stuck in sport mode, and check engine light is always on - so there is no hurry at all. (The check engine light is probably not so good for resale). Its very kind of you to offer to sort it out thanks - I wouldnt want to put you to any trouble. My son has the tactrix cable and the software, I believe he has reflashed own car so ill see what he thinks about it first- after all what can possibly go wrong?

 

With 5 v on the signal line the ecu "thinks" atmospheric pressure is 150 kpa absolute (romraider shows that). Actual atmospheric press is less than 100 kpa (abs) yet we haven't had any running problems which is why I was thinking that sensor didnt do anything important.

 

I've pulled engines out a few times, re built one and overhauled transmissions on older models, but you know removing that manifold to do the blanking plate looks like a mission  that id rather not embark on. The manual starts off by telling you to degas the air con! The valves might leak a small amount but its almost undetectable where the pump was connected so id be happy just to leave the blanking job for now. 

 

 

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22 hours ago, Andy_Mac said:

older than me

 

LOL Newest car I've ever owned in my 2001 Holden

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Ahh yes so that is an issue that deleting won’t fix then. The code is looking for differential pressure so the code will go away but it’ll still read the wrong atmospheric pressure. You won’t be stuck with sport with the delete. Imagine the only lingering issue could be incorrect fuel trims which you’ve had for the while time anyway.

 

No reason to degas the aircon

 

That’s my post from when I did it including links to walkthroughs.

With access to a Tactrix cable the whole thing becomes a heap easier. As long as he knows what he’s doing with regards to connecting, flashing and disconnecting you’re sweet. Can corrupt the ECU if done incorrectly, but it’s alot harder to get wrong than right.

You could get him to pull the ROM and delete it himself in ROMRaider or email it my way and I can do it then send the altered one back.

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