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Discussion Starter #21 (Edited)
I just reconnected the EGR vacuum line, and the engine idles the same.
I think it was coincidence that it started idling again when I disconnected that.
At this point, the idle is no different with or without the EGR line connected.

I feel like the engine may currently be operating in the Limp Home Mode.
I still only get the one DTC (P1155), and I have zero throttle pedal response.
It's idling at ~700 RPM and smells really rich. And one other interesting detail:
When I step on the gas pedal, the RPM's drop like some type of load is added.
The TPS reading doesn't change at all, just the RPM dips down to about 600.
There appears to be some type of load being added (electrical, maybe?).
Also, while it does currently idle, it clearly is not controlling the idle speed.
If I turn on the A/C, the RPM's drop way down and it stalls again.

Is there some method to confirm if it's actually operating in Limp Home Mode?
 

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Delete the EGR and see what you get.
 

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Discussion Starter #23
Delete the EGR and see what you get.
I have completely disconnected and plugged the EGR.
But that makes no difference. Everything still operates the same.
I'm starting to think something is screwed up with the ECU.
Is there anything I can check to confirm if the ECU is still good or not?
How can I tell if I'm in a Back-Up or Limp Home Mode?
 

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Get yourself a scan tool.
 

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Discussion Starter #25
Get yourself a scan tool.
I do have a scan tool. It's an Actron Auto Scanner Plus.
That's how I'm reading the DTC codes and data parameters I've reported.
What else should I do with the scan tool to help shed some further light?
 

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No one wants to spend a lot of money, but at some point it may be best to take the vehicle to a certified technician who can accurately diagnose and fix the issue. I'm not saying that to be a smart a**, just my opinion.
 

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Discussion Starter #27
No one wants to spend a lot of money, but at some point it may be best to take the vehicle to a certified technician who can accurately diagnose and fix the issue. I'm not saying that to be a smart a**, just my opinion.
I had a mobile mechanic come to the house this morning to check it out.
My hope was that he would have a more elaborate scanner than mine, which he did.
Despite that, he wasn't able to diagnose the problem, after two hours of looking.
I'm not sure who is actually a "certified technician" any more these days.
When it comes to Hyundai, I suspect that term only applies to the dealership.
The dealership will likely just start replacing parts and then charging me for them.
 

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Discussion Starter #28
I found a used ECU online that came out of the exact same model as ours.
Also literally all of the numbers on it exactly match all the numbers on mine.
I'm considering buying that one to try swapping it with mine to see what happens.
I realize that's quite a gamble, but I think it might be worth a try.
If that doesn't work, I guess I'll have to flatbed the car to the dealership.
All the problems started when the alternator died and the battery got run dead.
I can't help but think the ECU somehow got electrically impacted by something.

Are the ECU's plug and play, or would it need to be programmed to my car?
I don't see any way to readily open it up to swap out a calibration chip or prom.
Anybody have experience with swapping out their ECU..?
 

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Are the ECU's plug and play
I believe they are in the USA, because your cars don't have transponder key immobilisers.

If I helped you fix it, why not...

Your support is greatly appreciated
 

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What are your fuel trims doing? Throttle? Any load parameters are what we need to see.
 

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Discussion Starter #31
Hey, just to put some closure on this one, it was the ECU.
We located a used one on line for $80, and it finally arrived.
We installed it today, and everything is running great again.
Thanks Guys!
 

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Hey, just to put some closure on this one, it was the ECU.
Thanks for taking the time to post back and confirm the fix. The question you need to ask yourself now is what caused the damage to the original ECU. Because if there is some underlying issue it will likely damage the replacement ECU too.

If I helped you fix it, why not...

Your support is greatly appreciated
 

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Discussion Starter #33
Thanks for taking the time to post back and confirm the fix. The question you need to ask yourself now is what caused the damage to the original ECU. Because if there is some underlying issue it will likely damage the replacement ECU too.
Yes. I agree. The problem started after the alternator replacement described above.
My son ran it completely dead, while attempting to make it to the next exit, so we had it towed home.
It seems like somehow during that event, the ECU got scrambled.
 
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