SR20DET Limp Mode

[weirdchris555]

Hey everyone. I was wiring up my consult last night and ran into an issue on my redtop sr20det. The car was fine before this. I have nistune but everything has been working fine prior to this. I ran the wires over from the consult port to the ecu and left them there. I havnt tied into the ecu wires yet. Well I go to start the car and it runs fine. Then after a couple minutes of running it kicks into limp mode. I checked the code on the led on the ecu, but its constantly on. I have no idea where to begin. It happens after reseting the ecu too. I waited all night and it ran fine for a couple of minutes, but if I try to reset it by pulling the battery for a couple of minutes, it starts right up into limp mode. Please help me. Thanks

[OutlawLui]

check your maf, might have a bad connection

[weirdchris555]

Ok ill check it out. Worried something happened when I was tracing wires because everything was fine before all this.

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[weirdchris555]

Would having no O2 sensor throw the car into limp mode? I did a continuity test from the connector in the engine bay to the ecu pin for the O2 sensor and I'm getting nothing (ran through all 3 wires on the engine bay connector because I couldn't look up which was the signal wire). I had the car running in limp mode, then reached down touched for loose wires and as soon as I got near the O2 signal wire or the Coolant Temp the car kicked back in to normal mode and then when I let go kicked back into limp mode which in turn flooded the engine killing it. Also doubt its the MAF can rev past 3 grand.

[cotbu]

No! It would be open loop mode, not limp home mode! You're ecu you would never get the OK/ready from the 02 sensor and probably not getting the OK/ready from the coolant temp sensor either. Both would make your car run like shit!(too much fuel) but I wouldn't consider it the limp mode you'd have from a faulty mass air flow sensor.

Since you know you have at least one problem, fix it and see what happens or just stop them from shorting out!

[weirdchris555]

Easier said than done. Lol if there's a short its in the pin. Ill check it out later. Also just to verify this is limp mode.

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[OutlawLui]

Disconnect your maf plug, , inspect it closely and make sure each of the tiny small female plugs are not damaged, if they are than that could be why your getting shitty contact to the maf and going into limp mode. check the maf and o2 grounds for continuity with your multimeter and check your maf and o2 power wires to make sure your getting voltage wen your ignition key is on without staring the car

[weirdchris555]

Yep I just finished doing all that. The MAF had a good ground, got a good power, and had like 10 or so volts on the third wire when the car was just in the run. The o2 seemed to be grounding itself off, so I just went around and made sure everything was good with the ecu wiring and then checked the sensor again and it was not shorting out anymore. I havnt checked the temp sensor yet. I think its a poor connectiom at the ecu plug for at least the o2 sensor and possibly the coolant.

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[cotbu]

Not limp mode, fucked up wiring! How hard was it to fix the short again, since you know the wires you've touched!
You also have low voltage, mafs should have closer to battery voltage, so should the injectors. 10v at idle or even KOEO is low

[weirdchris555]

I still don't understand why you keep saying its not in limp mode. IT IS. There is no code, the LED is always lit when checking the codes, the fuel pump doesn't prime, running 9.5 A/F ratio etc etc. Its limp mode, directly from the FSM. Now as to why, thats what I am figuring out. Today I am checking the pins. If there is no connection and the ecu sees 0 volts from certain sensors (read zero, not some low value or high value etc), its going to kick to limp. Went and rechecked my MAF i was wrong, it was closer to battery voltage.

[cotbu]

It's not limp mode! By your standards and thinking, a fried ecu, a blown head gasket or blown piston is limp mode. I won't say it again. You have wiring issues, and or a faulty ecu. You are running in the knock map because there are major issues with your car. I can help you. Your problem is not the mafs, limiting your rev too 2500rpm nor do you have codes that say....... well anything! There is no limp mode that stops the fuel pump from priming. I guess you can say, any car that is running messed up is in limp mode!

Then again I would say check the ecu for codes!!!
Take your ecu and put it in another car with the same harness, and try to pull codes

[weirdchris555]

Here's a question for ya. I just ran through diagnostic 24, checking the MAF. So as I previously said, the positive voltage is good. I then went to check the continuity between the ground on the engine bay plug and pin 17 which is the MAF sensor ground. There was continuity. I proceeded to check the sensor wire continuity for the MAF and it was connected to the correct pin 16. I went back to the ecu plug and checked first the ECU ground which is pin 39 and that was a good ground.

Now comes the good stuff. I went to check the ground between what is title "Sensor Ground" which is pin 21, and there was no ground. I was wondering because I am not too sure but are all the sensor grounds run to that pin 21 which is sensor ground? I also checked the signal for the 02 sensor and that had continuity. The weird thing is like a couple of minutes later I double checked the 02 ground and it was fine. So I went back to check the "Sensor Ground" and it was no good.

If someone knows if all the sensors run to that "sensor ground" pin, that would help greatly since I think thats my problem child.

So to summarize, MAF has good continuity to 12 Volt power, to the ecu MAF ground pin 17, and to the MAF sensor signal Pin 16. The O2 has good Power, good ground to the chasis, and good signal wire to pin 19. Pin 21 titled "sensor ground" does not have continuity to a ground.

Just checked the TPS, Coolant temp sensor, and the cas. The coolant and the cas both had good grounds and continuity to the correct pins. The TPS on the other hand did not have a ground whatsoever but did have continuity to the correct pin for the signal. I may try grounding the tps later today as this would cause the issue at hand.

[weirdchris555]

Just as an update I got it out of limp/fail safe mode. I ran through every sensor except the knock sensor checking ground, sensor signal etc. Everything checked out. Went and started the car and it started fine. It was idling fine with a slight misfire occasionally so I went to pull the codes and there were none. Took it for a slight drive and it was running on the rich side. After driving around for a couple of minutes, I parked the car and it fell on its face in the parking lot and died. It had switched back to limp/fail safe mode which I verified by checking the ecu light constantly lit. I am straight up stumped.

As a side note when the car was completely cooled off, there was quite a bit of pressure under the radiator cap...weird.

[GhostlyCoupe]

I had this problem was well recently. It took a lot of digging to find the info about this issue.

The ECU will go into "solid red LED on" mode if it's not able to read the external ROM's containing the tuned maps when using a Nistune/whatever daughterboard.

I was able to fix mine by removing the card and reseating it.

You may not be as lucky and there may be a bad solder joint at the connector that was added.

[GhostlyCoupe]

Originally Posted by cotbu

It's not limp mode! By your standards and thinking, a fried ecu, a blown head gasket or blown piston is limp mode. I won't say it again. You have wiring issues, and or a faulty ecu. You are running in the knock map because there are major issues with your car. I can help you. Your problem is not the mafs, limiting your rev too 2500rpm nor do you have codes that say....... well anything! There is no limp mode that stops the fuel pump from priming. I guess you can say, any car that is running messed up is in limp mode!

Then again I would say check the ecu for codes!!!
Take your ecu and put it in another car with the same harness, and try to pull codes

The SR20DET does indeed have a "limp mode" . It defaults to pre-stored values under certain conditions which are hard coded into the ECU and illuminates the red LED on the ECU.

This is particularly annoying because when an SR20DET ECU is in this "limp mode" the consult port does not function, nor will the self-diagnostic modes (flashing lights) making it that much harder to diagnose.

[weirdchris555]

Originally Posted by GhostlyCoupe

I had this problem was well recently. It took a lot of digging to find the info about this issue.

The ECU will go into "solid red LED on" mode if it's not able to read the external ROM's containing the tuned maps when using a Nistune/whatever daughterboard.

I was able to fix mine by removing the card and reseating it.

You may not be as lucky and there may be a bad solder joint at the connector that was added.

Hmm I'll have to check it out. Maybe it got jostled a tad. Im pretty sure the solder is good. Like I said it was working fine until I went to wire up the consult. Thank you, I'll look into it.

...and yeah I gave up trying to explain limp/fail safe mode to that kid. Its so unfortunate that consult nor ecu codes work in that mode

[cotbu]

This is particularly annoying because when an SR20DET ECU is in this "limp mode" the consult port does not function, nor will the self-diagnostic modes (flashing lights) making it that much harder to diagnose.

This is not limp mode, there is no way for the ecu to protect the engine, if you drive with the ecu in this condition you will blow your engine! Yes, if you have a failed daughterboard installed it can cause the ecu led to stay lit, that is not limp mode.
If you install an ecu that is broken it will not automatically revert to limpmode. If you have detonation with the ecu and the led is lit it will not switch you over to the knock map. Not fucking limp mode

The SR20DET does indeed have a "limp mode" . It defaults to pre-stored values under certain conditions which are hard coded into the ECU and illuminates the red LED on the ECU

Yes the ecu does have a limp mode, if you can't read any data from the ecu it is not limp mode, if you have a board installed and you have jumpers set what makes you think it would read from the stock tune. just pull the chips out and you revert back to stock right?

Not a fucking kid! but glad you found new help good fucking luck!

[weirdchris555]

Listen. I am very greatfull for your help. I guess I just don't understand what you are saying. According to both the FSM and Nistune's own communications error pdf my ecu is in limp mode. There is no consult communication in limp mode, nor is there any ecu codes. It just stays lit. Maybe there is a fundamental definition difference between you and me? I have no idea. I'll look at it in the morning its been a long week.

[cotbu]

You listen, the terminology is wrong, fsm, nistune or whatever/ whoever, this is not limp mode!
Fail safe mode would not even be correct as a zilvia.net tech. I would prefer you don't use limp mode to describe your problem. That's all, you just don't understand why, feel me.

I think I know what you problem is, Seriously and I will do it for free, and an apology. Not to me but to the members of the forum. j/k
You probably have a messed up ecu, and some serious wiring issue.
We need to fix and verify or vice versa the ecu issue. You can't put a known working ecu's in your car. Do I really need to explain this????? You have to put your ecu in a known working ecu's vehicle or make a test bench<--- maybe not!
After you determine the condition of the ecu, you can send it to me or post HQ images w/macro and I edit them with pretty colors of things that need to be repaired. Now we'll go through your harness step by step and make repairs. I will hate you after this and only love you again, once you get your car running in tip top shape...! You'll hate me either way, be for warned!

I am rambling on but, just let me know if you want the help and we can start you recovery.
Speaking of recovery, I had this one guy keep yelling at me his phone was "bricked"! Just because he couldn't get into recovery mode, with 3button combo
and because the usb dongle/jig didn't put him into download. I showed him an alternate way to get download mode and he said it worked though a text to me! lol!

GhostlyCoupe, should know first hand that, sometimes they get it wrong!

It worked ! The value data scan had for the tp value was wrong

sorry for the rant and ramble but I know I can help!

[GhostlyCoupe]

Originally Posted by cotbu

You listen, the terminology is wrong, fsm, nistune or whatever/ whoever, this is not limp mode!
Fail safe mode would not even be correct as a zilvia.net tech. I would prefer you don't use limp mode to describe your problem. That's all, you just don't understand why, feel me.

I think I know what you problem is, Seriously and I will do it for free, and an apology. Not to me but to the members of the forum. j/k
You probably have a messed up ecu, and some serious wiring issue.
We need to fix and verify or vice versa the ecu issue. You can't put a known working ecu's in your car. Do I really need to explain this????? You have to put your ecu in a known working ecu's vehicle or make a test bench<--- maybe not!
After you determine the condition of the ecu, you can send it to me or post HQ images w/macro and I edit them with pretty colors of things that need to be repaired. Now we'll go through your harness step by step and make repairs. I will hate you after this and only love you again, once you get your car running in tip top shape...! You'll hate me either way, be for warned!

I am rambling on but, just let me know if you want the help and we can start you recovery.
Speaking of recovery, I had this one guy keep yelling at me his phone was "bricked"! Just because he couldn't get into recovery mode, with 3button combo
and because the usb dongle/jig didn't put him into download. I showed him an alternate way to get download mode and he said it worked though a text to me! lol!

GhostlyCoupe, should know first hand that, sometimes they get it wrong!


sorry for the rant and ramble but I know I can help!

I guess you better call Nistune and tell them to correct their documentation where they refer to this state as "limp mode" then.

http://nistune.com/docs/NIStune_Emulator_Tutorial.pdf

[GhostlyCoupe]

Here is the blurb on lump mode from Nistune. Yes, the car will run while in this mode but it does not run well and will not exceed 3000rpm. I have highlighted the section pertaining to the issue where you can see there is indeed a limp mode that will allow the car to run when a catastrophic issue happens.

The symptoms describe the OP's issues exactly, and this is the fix. That's all there is to it.

From: http://nistune.com/docs/Installation...iagnostics.pdf

Processor limp mode
Later model ECU's have an internal processor limp mode also. When the program from the ECU chip
or daughter board is not functioning, an auxiliary processor will inject a set pulse width for each
injection regardless of other sensor inputs and ECU program. When in limp mode, this will be indicated
to the operator through the means of a LED in the ECU

Processor limp mode is entered when a major fault has occurred. Major faults occur with anything to do
with the ECU micro code being unable to run. This can be a result of the various factors where the
processor is unable to execute the code properly. If it occurs after resoldering and resoldering then
there may be an introduced problem causing the ECU to go into processor limp mode.
The processor bus on any ECU consists of 8-16 data lines and 16 address lines plus control lines. If
any of these lines is broken or shorted during the installation process, it will stop data flowing correctly
on the lines and the ECU will not be able to run properly.

Symptoms vary depending on engine (specifics covered in the relevant section for each engine) but
one thing is constant across all engines – Consult communications will NOT be active in limp mode. So
you will not be able to connect to it.



Engine running badly is defined as engine may start but idle will be poor and engine will overfuel badly,
resulting in obvious clouds of partially burnt fuel coming from exhaust. Engine may not run at all if
injectors and/or AFM are non-standard. May lean out when rev exceed 2000rpm

Signs of limp mode on common ECUs:

• Check engine light and/or ECU LED will stay on
• Will not be able to connect to the ECU using consult
• When IGN is turned on fuel pump will only pulse on momentarily rather than running for 3 to 5
seconds.
• Engine will not run correctly. Engine may start but idle will be poor and engine will overfuel badly,
resulting in obvious clouds of partially burnt fuel coming from exhaust. Engine may not run at all if
injectors and/or AFM are non-standard. May lean out when rev exceed 2000rpm

If you’ve performed the NIStune board install yourself and the ECU has gone into limp mode then
please check the following:

• Soldering of 20+20 header. Clean flux from all joints and inspect each joint using an eyeglass
and a good light. In particular look for solder bridges between pins and slugs of solder on the ECU
• Check that tracks have not been cut by pushing too hard on the desoldering gun
• Check that you have moved the necessary jumper(s) for the ECU to use the daughter board
• Check the part number on your board matches your ECU number when possible

[cotbu]

They used the term loosely there, and tell you what to check. And it is considered acceptable as they are providing the install guide and can call if fubarred, if they wanted too. This is not a Nistune specific forum, So saying limp mode and using it like the OP did is truly confusing.

The revision on that manual is over due true, but it's theirs and when they help you, they will probably refer to it.

BUT THIS IS ZILVIA!!!



I just wanna comment here,

Yes, the car will run while in this mode but it does not run well and will not exceed 3000rpm

This would indicate a mafs malfunction to me, and probably every other member as well, That would be limp mode. When The ecu diagnostic led is lit the car will rev past 3000rpm but clearly have issues, I can probably tell you other things it will do that contradict what the Nistune guide say's. I just wanna say I'm not new to this and just because it's written. documented and spewed over and over doesn't make it law!

Stop calling a F'ed up install of a daughter board, limp mode!

[GhostlyCoupe]

/facepalm

The limp mode is part of the programming in the ECU from NISSAN .. has nothing to do with the daughterboard.

Here are the excerpts from NISSANS FACTORY SERVICE MANUAL

[cotbu]

I never said our ecu's don't have a limp mode/fail safe mode! Not fucking once. The mode you and the op stated earlier are not the same as what you are posting now! The LED on OBD2 ECU's stay lit till cleared or repaired. ON OBD1 if you have an check engine light or ecu led on while the engine is running, something is seriously wrong! Most likely cause wiring or ecu! Like a fucked up a daughter board install.

Your last post is a normal operating ecu. Not some fucked solder job to a 40pin header
Cali car's are a little pickier but neither one of you newbs are from California

Originally Posted by GhostlyCoupe

/facepalm

The limp mode is part of the programming in the ECU from NISSAN .. has nothing to do with the daughterboard.

Here are the excerpts from NISSANS FACTORY SERVICE MANUAL

Stop calling a F'ed up install of a daughter board, limp mode!

[GhostlyCoupe]

I'm sure the guys over at PLMS developments will get a kick out of seeing this thread and being told they have no idea what they are talking about.

I guess you aren't getting how this works. The ECU runs mode 1 diagnostic automatically. I.E. when the ignition is turned off, it returns to mode 1. During mode one diagnostic operation with the engine ON, if there is a fault the ECU will illuminate the check engine light and the red LED and place the car into FAIL SAFE MODE as indicated by the FSM excerpt. This is NOT the same as the mode 1 diagnostic with the engine OFF which is used to check the function of the indicator and LED!

A "f'ed up install of a daughter board" causes a mode 1 malfunction, which causes the ECU to be "stuck' in mode 1 because mode 1 will not clear and allow you to read mode 2 trouble codes unless the fault is corrected. In this case, the fault will remain because the ECU cannot communicate with the daughter board so the LED stays on, and it's stuck and you cannot use CONSULT or other diagnostic modes!

[cotbu]

Stop calling a F'ed up install of a daughter board, limp mode!

An ecu malfunction is a much better term to describe this issue, than limp mode. IMHO
Like I said, if you write the book you can call it what you want!

You keep editing your post, like a 5yr old dude. me too! If you would have put this much effort in you other post,

It worked ! The value data scan had for the tp value was wrong

You probably would have figured it out by yourself
And why not ask NDS to update that data for yuuuuh chea!

PS if pete does come here and pee on me, I'd just cover my eyes and open my mouth and add that knowledge as to what constitutes as LIMP MODE
Then every time someone says they're in limp mode or can't rev past 2500rpm, I'll ask them to check if the ecu led is lit and can you pull codes or connect to consult port?

[weirdchris555]

I can honestly say I have no idea what is going on in here. Lol going to check out the car later with a short drive. It's running properly now but that was at cold startup

[weirdchris555]

Ok its out of the mode. I was finally able to connect my consult port to my laptop. There are no codes (well it says something about new_ok or something along those lines). When its cold, it runs ok and idles ok. I didn't get a log yet of cold, but when warm I did. The 02 sensor voltage was constant at 1.27. Its a new sensor too, which is leading me to the connections. I think its wreaking havoc because when its warm, my wideband is reading around 10 and dipping into the 9s and has a rough and hunting idle. Timing is jumping and so is the maf. Mehh.

[GhostlyCoupe]

Is it showing code 55?

Which ECU are you using and which O2 sensor?

[weirdchris555]

ECU number 62. Stock redtop ecu with a type 3 board installed. No codes. It was running fine with the board etc prior to all of this. Stock redtop o2 sensor (skinny) just got it a couple of months ago from nissanparts.cc When its cold it runs in normal mode. Albeit a tad on the rich side and kinda hard to start. Once it has warmed all the way up though, it goes into that 9.5ish A/F ratio mode with the LED lit. I managed to grab a log all the way up to that mode until the consult port shut down. I have no idea what is going on.