P1127 1.8L cam and ECU
Thread Starter
Senior Member
Joined: Nov 2007
Posts: 429
Likes: 0
From: Toronto, Canada
P1127 1.8L cam and ECU
I hope Stocker can get on this thread, as I'm seeing something similar to him:
https://www.hyundaiaftermarket.org/f...in-last-night/
I had the same problem as Stocker: P1127. And I think I know what's wrong, but I'm not sure exactly how to fix it. Check this out ...
As you probably know, I installed the beta2 block and cylinder head on my RD1 tib. I had the machine shop work on the head. When I put back my engine about 2 years ago, I changed my ECU to the 1.8L. No CELs. I drove for maybe 6 months, no CELs. Then I decided to open up the cylinder head cover and replace my beta2 2.0L cam with the beta1 1.8L cam. I just wanted to try it out.
After I put everything back together, I decided I didn't like the 1.8L beta1 cam on the beta2 head (too rough, too loud), so I took it off and put back my beta2 cam. (remember, I still had the 1.8 ECU). Immediately after, I got P1127.
After a bunch of diagnosis, the only thing that fixed the P1127, was replacing my 1.8ECU with my original beta1 2.0 ECU.
I'm pretty sure that the problem is how the cam was replaced. Could it be that it was put back on with it being slightly off, somehow?? When the machine shop put it on for me, I had the 1.8L ECU and no problems. When I messed around with the Cam, that's when I started to get that code.
https://www.hyundaiaftermarket.org/f...in-last-night/
I had the same problem as Stocker: P1127. And I think I know what's wrong, but I'm not sure exactly how to fix it. Check this out ...
As you probably know, I installed the beta2 block and cylinder head on my RD1 tib. I had the machine shop work on the head. When I put back my engine about 2 years ago, I changed my ECU to the 1.8L. No CELs. I drove for maybe 6 months, no CELs. Then I decided to open up the cylinder head cover and replace my beta2 2.0L cam with the beta1 1.8L cam. I just wanted to try it out.
After I put everything back together, I decided I didn't like the 1.8L beta1 cam on the beta2 head (too rough, too loud), so I took it off and put back my beta2 cam. (remember, I still had the 1.8 ECU). Immediately after, I got P1127.
After a bunch of diagnosis, the only thing that fixed the P1127, was replacing my 1.8ECU with my original beta1 2.0 ECU.
I'm pretty sure that the problem is how the cam was replaced. Could it be that it was put back on with it being slightly off, somehow?? When the machine shop put it on for me, I had the 1.8L ECU and no problems. When I messed around with the Cam, that's when I started to get that code.
Super Moderator
Joined: Sep 2001
Posts: 10,795
Likes: 5
From: Pflugerville, TX
Vehicle: 2000 Elantra
www.hyundaitechinfo.com > DTC section > ELANTRA(RD) >2000 > G 2.0 DOHC > Engine > Engine Control > DTC - P1123, P1124, P1127, P1128 (AIR-FUEL CONTROL) > Diagnostic Procedure
Unless you put the MAFs on backwards and then reversed it at the time your P1127 went away, the computer may very well have taken a dump. It happens, but the timing is a frustrating coincidence. I don't recall exactly what I did to get rid of the P1127. I know I have been running the 2.0 computer several years now and that may have been the reason I changed back from the 1.8 computer. I don't recall it running different or getting better fuel economy with the different ECM, but just thinking about having a CEL pop up all the time makes me want to change my computer even now - so yeah, that probably was it.
The intermittent P1128 I mentioned in that thread, by the way, was a bad O2 sensor.
Unless you put the MAFs on backwards and then reversed it at the time your P1127 went away, the computer may very well have taken a dump. It happens, but the timing is a frustrating coincidence. I don't recall exactly what I did to get rid of the P1127. I know I have been running the 2.0 computer several years now and that may have been the reason I changed back from the 1.8 computer. I don't recall it running different or getting better fuel economy with the different ECM, but just thinking about having a CEL pop up all the time makes me want to change my computer even now - so yeah, that probably was it.
The intermittent P1128 I mentioned in that thread, by the way, was a bad O2 sensor.
Thread Starter
Senior Member
Joined: Nov 2007
Posts: 429
Likes: 0
From: Toronto, Canada
Thanks, Stocker! Could be a coincidence that the 1.8L ECU took a dump immediately after I removed the 1.8cam and replaced it with the 2.0beta2 cam, but man, talk about COINCIDENCE!! I was thinking that maybe it was the way I put the 2.0cam back - I remember reading that the engine isn't exactly leveled, so I was thinking that maybe I positioned the 2 notches on both cams, facing slightly towards the back of the engine when it should've been directly upwards.
I could live with the 2.0L ECU, but I got better mileage with the 1.8ECU, that's why I really wanted to put it back on (but without CEL's, of course)
I could live with the 2.0L ECU, but I got better mileage with the 1.8ECU, that's why I really wanted to put it back on (but without CEL's, of course)
Super Moderator
Joined: Sep 2001
Posts: 10,795
Likes: 5
From: Pflugerville, TX
Vehicle: 2000 Elantra
Well if you think about it, there is no better time for the computer to fail than when you have been handling it. All it takes is one time rubbing your plastic-clothed self on the plastic carpet to make enough voltage to kill the computer with one touch to the connector. ESD sucks.