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Rb25det Neo - Code 21 & Cylinder 1 Dead

syncade

By syncade,
in Engines & Forced Induction

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syncade Contributor

syncade

Posted
Posted

I recently acquired a consult -> USB cable and discovered Code 21: Ignition Signal Circuit. Im from the USA and i put this rb25det neo into an s14. Im running the car on a Stagea R34 Automatic ECU. I did a search on the forum and did read some other threads with a similar problem, but none helped. The motor has been running for a few weeks, but I cant get cylinder 1 to fire. I rotated the coils and plugs around so thats not the problem. Power voltage to coil 1 is your normal 12-13.5V, but the trigger voltage was only .3V (all other coils were ~.8V). I know my problem is either in the ECU or Wiring Harness, but i also read a thread on here where someone had a bad ground? Should i test the continuity to coil 1?

What do you guys suggest. Ive pretty much tried everything I can think of. I dont have access to try someone elses ECU or Wiring harness, as there are only a handful of these motors in my entire country. How often do these ECUs go out? I tried to test the voltage coming out of the Ignition Signals to each coil (directly on the ecu), but I couldnt get a reading for the life of me. Besides this one problem, the motor starts, idles, and drives as good as it gets (with 5 cylinders that is).

Please help me out here gents!

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https://www.sau.com.au/forums/topic/239162-rb25det-neo-code-21-cylinder-1-dead/
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naga Collaborator

naga

Posted
Posted

I don't think you can check the ecu trigger signal using a multimeter gotta use oscilloscope. I've done this on my car coz it was misfiring.

post-2214-1223473736_thumb.jpg

The signal should have a sawtooth sorta pattern (i think it's current control). If you don't get a signal it's proabbly either the wiring for the trigger signal is stuffed or the ecu itself is stuffed. You can check the wiring by just checking teh resistance from teh corresponding ecu pin to the coilpack connector for your dead cylinder.

How do you know the cylinders not firing anyway do you get blacksmoke out the exhaust?

syncade Contributor

syncade

Posted
  • Author
Posted
I don't think you can check the ecu trigger signal using a multimeter gotta use oscilloscope. I've done this on my car coz it was misfiring.

post-2214-1223473736_thumb.jpg

The signal should have a sawtooth sorta pattern (i think it's current control). If you don't get a signal it's proabbly either the wiring for the trigger signal is stuffed or the ecu itself is stuffed. You can check the wiring by just checking teh resistance from teh corresponding ecu pin to the coilpack connector for your dead cylinder.

How do you know the cylinders not firing anyway do you get blacksmoke out the exhaust?

I know because ive disconnected the coils during idle and the motor doesnt change at all. I rotated the coils and plugs, so I know its either wiring or the ECU. How would I check the resistance on the wiring to coil one? Just complete the loop by running a wire directly from the coil to the pin on the ecu?

Thanks for the help my friend, I do appreciate it.

KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted
I know because ive disconnected the coils during idle and the motor doesnt change at all. I rotated the coils and plugs, so I know its either wiring or the ECU. How would I check the resistance on the wiring to coil one? Just complete the loop by running a wire directly from the coil to the pin on the ecu?

Thanks for the help my friend, I do appreciate it.

Do you have a pinout diagram? This may be the one although there are variations:

http://www.skylinesaustralia.com/forums/in...st&id=31087

syncade Contributor

syncade

Posted
  • Author
Posted
Do you have a pinout diagram? This may be the one although there are variations:

http://www.skylinesaustralia.com/forums/in...st&id=31087

Yes i have the pinouts, thanks though. Im very surprised nobody has ever had this problem before?

666DAN Grand Master

666DAN

Posted
Posted

Open the ECU and check out the two large power transistors bottom left (plug facing you) up against the side, heatsinked to the body of the ECU.

I'm guessing the one of them will show signs of burning out, will be brown/charred and very brittle....to the point when you remove the heatsink to get a clear look it will break.

That's my guess, I've seen it before on R34 ECUs, hopefully I'm wrong.

jeffworld2 Veteran

jeffworld2

Posted
Posted

4x now i have seen error 21 keep a car off the road for months with the owner scared to drive it, 4x now i have switched to new coils and its been fine.

that being said, if your cylinder is dead completely, it may also be the wiring to that coil

syncade Contributor

syncade

Posted
  • Author
Posted
4x now i have seen error 21 keep a car off the road for months with the owner scared to drive it, 4x now i have switched to new coils and its been fine.

that being said, if your cylinder is dead completely, it may also be the wiring to that coil

I dont think it is the coils, as when I rotate them, the same cylinder wont fire. Im guessing at this point it must be wiring.

jeffworld2 Veteran

jeffworld2

Posted
Posted

so disconnect the ecu, isconnect the bad coil clip, and use the pinout diagram and a multimeter on the contnuity setting to get a simple answer of wether or not the cables get to the other end or not. with ecu and battery off, you can poke wherever you want and cant hurt anything.

check that one pin goes to ground, one goes to the battery, and the other will be the trigger for example if there are 3.

use a bit of speaker wire or something to go up from the ecu to one of the pins, and then find the other end on the ecu.

syncade Contributor

syncade

Posted
  • Author
Posted

Well i have continuity between the ecu and the coil on all 6 coilpacks, so I'm definitely thinking it is the ECU at this point correct?

And BTW, it's cylinder 6 that wont fire, not cylinder one. I was backwards on my counting order.

  • 9 years later...
  • 1 year later...
Rusty Nuts Experienced

Rusty Nuts

Posted
Posted
8 hours ago, bistratoaie said:

I seem to have the same problem and cylinder 6! Anyone got any solution?

I just read everything in this post, seems to me all the answers are there. It boils down to continuity or fried ECU.

  • 5 months later...
bistratoaie Explorer

bistratoaie

Posted
Posted

Turns out piston #6 had shat itself and got a little hole in it as fuel was just dumping into the sump, have done a rebuild with new forged pistons, rings, bearings etc and she's running beautifully. Ignition circuit also goes hand in hand with knock sensors I believe, I had an ignition fault code 21, and tried everything to sort it after buying new splitfires, spark plugs, coilpack harness, AFM all that jazz, turns out one of my knock sensors was crushed and that was my ignition problem solvered ☺️

  • Like 1
KiwiRS4T Grand Master

KiwiRS4T

Posted
Posted
On 6/30/2019 at 11:45 PM, bistratoaie said:

Turns out piston #6 had shat itself and got a little hole in it as fuel was just dumping into the sump, have done a rebuild with new forged pistons, rings, bearings etc and she's running beautifully. Ignition circuit also goes hand in hand with knock sensors I believe, I had an ignition fault code 21, and tried everything to sort it after buying new splitfires, spark plugs, coilpack harness, AFM all that jazz, turns out one of my knock sensors was crushed and that was my ignition problem solvered ☺️

It occurs to me that a compression test might have been a good idea. Is that how you found the fault?

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