What would make the ECM go into limp home mode?

[The Yeti]

Why would the ECM go into limp home mode and how do you fix that? I am having an issue with my Typhoon running excessivly rich with no codes. It has a built engine with 50lb injectors and Phil long chip. Ran great until last week when I installed a battery box for the battery that was already relocated in the trunk. I am at a loss and ready to sell the truck. I can't drive it because it runs so rich and bogs down under any acceleration.
I have removed the ECMb fuse and the negative of the battery for 2 days and it runs perfect first start up but from then after the truck runs like shit, pig rich stalling out and not being able to rev under load. I am assuming it is limp mode. It runs so rich I have black stains on my driveway and garage from the tailpipe- no lie.

 

[KDBL1TY]

Re: What would make the ECM go into limp home mode?

Sounds like you need to check your fuel pressure, start there and look at plugs, fuel pressure regulator . I dont have all the high tech computer stuff. Im old school check the knowns and move forward from there. No codes is whats really weird.

 

[WyoSyclone]

Re: What would make the ECM go into limp home mode?

Have you tried taking the chip out and re-seating it? If it's truly in limp mode, I would say there is something wrong with the chip, or the ECM....

 

[ShuggsRR]

Re: What would make the ECM go into limp home mode?

Mine was in limp home mode because of a weak alternator. Another time was because of a loose ground from the battery

 

[typhoon92]

Re: What would make the ECM go into limp home mode?

I would try changing out the 3 bar map sensor...

 

[cloneman315]

Re: What would make the ECM go into limp home mode?

did you have a ugly chick in the passenger seat to maybe make it go limp?lol x 2 on the map any codes?check coolant sensor for the right reading,on datamaster etc

 

[turbodig]

Re: What would make the ECM go into limp home mode?

Do the paper-clip trouble code check. If it flashes the normal code 12, the ECM and sensors are fine.


A scan tool of some variety would help loads. You can buy a cable for $60. You can download software for free. Blindly swapping parts is going to cost you much more than that.


80% of backup ECM issues in these things has to do with a bad, loose or improperly installed chip (ie, piggyback module with no MEMCAL plugged into it.

The other 20% is generally a dead ECM.

 

[The Yeti]

Re: What would make the ECM go into limp home mode?

Do the paper-clip trouble code check. If it flashes the normal code 12, the ECM and sensors are fine.


A scan tool of some variety would help loads. You can buy a cable for $60. You can download software for free. Blindly swapping parts is going to cost you much more than that.


80% of backup ECM issues in these things has to do with a bad, loose or improperly installed chip (ie, piggyback module with no MEMCAL plugged into it.

The other 20% is generally a dead ECM.

I used a scanner yesterday and only got code 12 (normal). Again it ran great after leaving the battery and ECMb fuse disconnected for a day and the next startup= same crap, died on first startup, have to hold the gas pedal to the floor to start it up and do the same to keep it idling. Idle spikes 400 rpms or so until it warms up.
Nothing, literally nothing was disconnected from the system when I installed the battery box. I just lifted the battery up still connected to the system and dropped it in. Very frustrating...

 

[cloneman315]

Re: What would make the ECM go into limp home mode?

check that coolant sensor to see if it is reading right in the scan tool,not just a code,

 

[cloneman315]

Re: What would make the ECM go into limp home mode?

did one of those grounds come unplugged on the fender?

 

[SY2932]

Re: What would make the ECM go into limp home mode?

did one of those grounds come unplugged on the fender?

Ditto. If the truck was running fine before you messed with the battery box, I would give anthing associated with that a very good looking over. Bad electrical grounds will give you headaches so big, even excedrin won't help.

 

[TYTILIDIE]

Re: What would make the ECM go into limp home mode?

Why when people cant figure out whats wrong with their trucks do they always threaten to sell it? I say sell it if you dont want to get dirty. From the sound of it you havent done much to figure it out. There could be 50 things wrong with it and the fact that there is no code means squat. In fact, 70% of the time something has gone wrong with my TY I never got a CEL. I'd get used to it. What scanner are you using? Do you have a laptop with Data Master?

 

[midnightbluS10]

Re: What would make the ECM go into limp home mode?

Why when people cant figure out whats wrong with their trucks do they always threaten to sell it? I say sell it if you dont want to get dirty. From the sound of it you havent done much to figure it out. There could be 50 things wrong with it and the fact that there is no code means squat. In fact, 70% of the time something has gone wrong with my TY I never got a CEL. I'd get used to it. What scanner are you using? Do you have a laptop with Data Master?

I concur. I'd never sell my Blazer...even after the whole month and something it took me to get it running after I screwed it up.

 

[bezerk]

Re: What would make the ECM go into limp home mode?

have you tried, that when the engine is warm take out the 2 fuses and try it again?

 

[GAShan]

Re: What would make the ECM go into limp home mode?

Ignition module in distributor may be bad.

 

[The Yeti]

Re: What would make the ECM go into limp home mode?

Selling a vehicle is a reality when it is running poorly and in this case is undriveable. I love my Viper but daily driving an excessivle modded one is out of the question, that is why I have a not even midly modded Typhoon. I am going to trace the ground back but from memory it is just below the battery on the frame attached securly.
I pulled the ECM down today, got a ribbon cable running into the center console area- I assume it has to do with the chip as it goes into the ECM case. One of the previous owners left the security system and amplifier wiring all over the place, so I guess I will clean it up while I am down there.
Anyone have a spare ECM? Resetting it works now for about 20 minutes of driving or 2nd startup if less driving until it goes pig rich.

 

[The Yeti]

Re: What would make the ECM go into limp home mode?

have you tried, that when the engine is warm take out the 2 fuses and try it again?

Yes, it runs like crap until I keep the fuse removed for atleast 10 hours. The ECMb fuse is the only one that seems to make a difference, I removed the other one for about 12 hours and nothing.

 

[The Yeti]

Re: What would make the ECM go into limp home mode?

Why when people cant figure out whats wrong with their trucks do they always threaten to sell it? I say sell it if you dont want to get dirty. From the sound of it you havent done much to figure it out. There could be 50 things wrong with it and the fact that there is no code means squat. In fact, 70% of the time something has gone wrong with my TY I never got a CEL. I'd get used to it. What scanner are you using? Do you have a laptop with Data Master?

Dude, I am on here to try and solve the issue. I don't know what half this scan stuff is you all are talking about, the only thing I have done to pull codes is use a scanner from autozone and it blipped the check engine light for just the 12 code. I have a laptop, what is data master and where do I get it/download it from and where does it physically plug in? I was hoping to find someone in FL to give me a hand, I mainly work with Ford and Mopar and my shop, I was hoping my Typhoon would not need to fall into that catagory.

 

[bezerk]

Re: What would make the ECM go into limp home mode?

i meant. the ecm goes into learning mode when you reinstall the ecm fuses. i was saying that once your engine is at operating temp. take fuses out for a few seconds, and reinstall them and maybe it will leanr it selve to be good.
also you need a scan tool to see what kind of values you have

 

[The Yeti]

Re: What would make the ECM go into limp home mode?

Okay, help me tell what I am looking at. I dropped the ECM and removed the cover. Chip says V5-50, I'd have to assume that is Phil Longs chip. (Remeber guys, I did not build the truck-I bought it and since have been improving it along the way). Also there is a ribbon cable going to under the cup holder and looks molded but I assume is not. It has a LED with a 1-like 6 and some numbers and a knob that moves into multiple positions to change the LED. Never knew what it was and left it alone but now that the truck is apart I will ask: