# Code P1124 engine won't start.



## M-train (Mar 4, 2014)

Its an 03 Altima 2.5S [QR25DE] auto tranny. I completely rebuilt the engine last week.

I also changed out the hard to get to crankshaft sensor, as well as the cam sensor. 

I tried to crank it yesterday, and it wouldn't start. I got a code P1124 which is the throttle body shorted out, or bad relay. 

I also rechecked the timing chain alignment, and it was where it should be. 

So will a bad throttle body [fly by wire, no linkage], or bad tb relay keep this thing from starting?

Oh, and I also did a compression check, and it passed.


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## rogoman (Dec 16, 2004)

First thing to do is check for spark on all cylinders and fuel pressure. If they're OK, then the injectors may not be firing. Check all the engine grounds and harness connectors. 

With a P1124 code set, you should still be able to start the engine. However it will be in 'failsafe' mode.


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## M-train (Mar 4, 2014)

How do you check for spark?


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## M-train (Mar 4, 2014)

Ok, I have another running 03 Altima 2.5S auto. 

So today I changed out the throttle bodies, and the old throttle body worked fine on the gold Altima. [the Silver Altima is the problem, but both have new rebuilt engines].

Then I changed out the new mass air meter from the silver car to the gold, and again on the gold car it ran fine 

Then I changed out the throttle relay from the silver to the gold, and again it was fine. 

This car, the silver car did run when I bought it. However if you goosed the gas pedal it would die. You could drive the car just a bit by modulating the throttle. 

The code I got before I pulled the engine was a faulty mass air meter. There was also a problem where someone didn't get the hose that joins the throttle body back on so there was a huge leak there. 

While I was pulling relays I found some water had gotten into the wiring. So I pulled ALL relays, and connections, and blew them out with compressed air, and then put just a drop of oil on all of the connections before putting it all back together. 

Now when I connect the battery the outside headlights stay on! I've tried everything to get them to go off, but the only way I can find is to pull the neg batt terminal.


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## SPEEDO (Jun 9, 2003)

they have greese just for electrical connections (dont use oil) I wonder if the sensor on the gas pedal (talks to tb) might have a issue, have you changed it with the other car? was the vehicle in a flood?


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## M-train (Mar 4, 2014)

Vehicle was running when I bought it. The only code I got before I pulled the engine was for a faulty mass air. 

I changed out everything from a running Altima of the same year, and that car ran fine with the interchanged parts. 

I'm still wondering about the timing. 

Before taking the engine apart I pulled the crank pulley to align with the top mark on the block [after the timing cover was off].

I then marked the teeth that were directly opposing each other on the cams. I didn't use the colored marks on this engine. 

Question, is it easier to pull the timing cover, and upper oil pan with the sub frame dropped?


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## M-train (Mar 4, 2014)

Update:

I mentioned that the outer headlights on both sides won't turn off until the battery is disconnected. 

After a bit of research I found that the BCM might need to be reset, and the changing out to a new BCM won't cure the problem unless its reset by Nissan, as the computer won't recognize your ignition keys.

I wonder if that is the problem as I took great pains to get the timing right when the engine was apart. 

Here is the link.
2006 Nissan Altima Replacing BCM: Computer Problem 2006 Nissan ...


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## rogoman (Dec 16, 2004)

M-train said:


> How do you check for spark?


Very simple to do. Get a spare spark plug and pull each coil pack one at a time; plugin the spare spark plug and lay the assembly on some ground point so that the spark plug base is grounded. Have someone spin the engine while watching for a spark.


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## M-train (Mar 4, 2014)

I'll give this a try later on at dusk so I can better see the spark.

Question, I read somewhere that after 5 failed attempts at starting the computer will enter into "shutdown mode" as a security measure. 

If this is true, then it won't matter what I do as its not going to start. 

Do all 03 Altimas have this?


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## M-train (Mar 4, 2014)

Ok, it does have spark on all plugs although a weak red, not a bright blue. 

I really hate to take it to the dealership as they have a pretty bad rep for rip offs.


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## M-train (Mar 4, 2014)

Anybody?.......


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## M-train (Mar 4, 2014)

Well, today I pulled the compression tester back out, and tested ALL of the cylinders [not just one as I did first time round].

Number 2, and number 4 cylinders were way down. Number 2 was at zero, while number 4 was a whopping 30 compared to the other two at approx 150.

So, I just going to pull the engine to see what is going on.


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## rogoman (Dec 16, 2004)

With a properly rebuilt engine, the compression should at least be in the range of 153 - 181 psi; once the engine is run-in, the compression should be around max. Try putting some oil into the cylinders to see if the compression comes up; if it comes up, there may be sealing problems with the rings. Otherwise I would venture to say that the timing chain may have been incorrectly installed resulting in bent valves. This can be verified by a leak down test.


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## M-train (Mar 4, 2014)

I don't think there are any bent valves as I ALWAYS turn the engine over by hand BEFORE starting with the starter just to make sure there is no interference. 

This should be mandatory for any engine builder, like me. 

I'm thinking its the exhaust valves, as I didn't have access to a valve machine [My father has a valve machine, but the stone is gone so I ordered a replacement last night]. 

I hand lapped the valves, and checked everything for leaks with gas, but it bugged me. 

I tried a few drops of oil down the cylinder when I did the comp check, and unfortunately it didn't help. 

Hopefully today I will know something.


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## M-train (Mar 4, 2014)

Annnnnnnd the answer was "D" none of the above.


It turned out to be a broken exhaust cam........which is a bit better as I don't have to pull the head.


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## rogoman (Dec 16, 2004)

Good to hear that you've found the problem. At least it looks like it's not catastrophic. After you replace the cam, it'll be a good idea to do another compression test on all cylinders before you try to fire it up to insure good compression.


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## M-train (Mar 4, 2014)

Yes, I definitely will do that as I DON'T want to pull the engine again.


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