Limp mode question

[98k2500]

I had an an 08 Tundra a few years ago. It would throw a code about every other day. When the CEL would come on it would go into limp mode. I'd clear the code and it would go out of limp mode.

The reason I bring this up is I now have a 98 k2500. I changed the distributor a few days ago and the CMP is at 0.8. I now have no SES light on. Before I changed the distributor the engine light was on and it felt like the truck was in limp mode. I haven't had a chance to drive it yet.

My question is now that I don't have any SES light on should I expect it to be out of limp mode, if it was in fact in limp mode?

 

[thegawd]

limp mode is caused by low or no volatge to the trans. it is usually caused by a faulty ignition switch where every time you turn the key may give you a different response. this is due to carbon build up on the contacts inside the switch. but it can be caused by a blown fuse, faulty wiring or a simple as the trans plug has come unplugged. there is only 1 wire that brings 12v+ to the tranny. it's on pin E of the big round plug. it should always read the exact same voltage as the battery if it's not then you probably need a new ignition switch. Pin E is a pink wire, it also supplies power to the heater part of the O2 sensors and if this wire shorts it will pop the fuse and put you into limp mode.

Limp mode is the following in a 4L60E:

a check engine light with like 6 transmission codes.
No Speedometer
No PRNDL gear indicator light on the dash
you start in 3rd gear but can manually shift from 1st or 2nd to get moving.

Al

 

[98k2500]

limp mode is caused by low or no volatge to the trans. it is usually caused by a faulty ignition switch where every time you turn the key may give you a different response. this is due to carbon build up on the contacts inside the switch. but it can be caused by a blown fuse, faulty wiring or a simple as the trans plug has come unplugged. there is only 1 wire that brings 12v+ to the tranny. it's on pin E of the big round plug. it should always read the exact same voltage as the battery if it's not then you probably need a new ignition switch. Pin E is a pink wire, it also supplies power to the heater part of the O2 sensors and if this wire shorts it will pop the fuse and put you into limp mode.

Limp mode is the following in a 4L60E:

No Speedometer
No PRNDL gear indicator light on the dash
you start in 3rd gear but can manually shift from 1st or 2nd to get moving.

Al

Is it the same on the 4l80E ?

 

[stutaeng]

I've read this limp mode on the 4L80e. Read here: https://www.gmt400.com/threads/4l80e-stuck-in-limp-mode.46392/page-2

Also read the ECU reduces power if the transmission temperature gets too hot, not sure.

On the newer vehicles I would imagine limp mode would have more logic programmed into it, such as going into limp mode if engine coolant temperature gets too hot, etc. These trucks didn't have that kind of programing back then.

What engine code do you have?

 

[thegawd]

I dont have any experience with the 80E... I'd imagine the same causes but different symptoms.... Stuataengs posted the info right there...

Al

 

[98k2500]

I've read this limp mode on the 4L80e. Read here: https://www.gmt400.com/threads/4l80e-stuck-in-limp-mode.46392/page-2

Also read the ECU reduces power if the transmission temperature gets too hot, not sure.

On the newer vehicles I would imagine limp mode would have more logic programmed into it, such as going into limp mode if engine coolant temperature gets too hot, etc. These trucks didn't have that kind of programing back then.

What engine code do you have?

The code I had was p1351. I just bought this truck to fix it up and I am new to these trucks so I'm just learning about them.

When I drive it down my street it did not have any power and engine ran rough. It was misfiring pretty bad. I replaced the spider poppet injectors with the mfi ones. Then I replaced the distributor and engine is idling much better. Still has a slight misfire.

I'm going to take it for a spin when I get home today but if it still doesn't have any power I need to figure out if it's in limp mode or if it's a different issue.

 

[stutaeng]

Check out this video:

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Maybe the ICM is bad, causing the miss?

 

[98k2500]

Check out this video:

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Maybe the ICM is bad, causing the miss?

I'll check into this. Thanks.

There is also two gren wires coming out of the wiring harness that has the connector all smashed up. The wires are pretty long coming out of the harness on the driver's side but they reach all the way to the front of te truck. Not sure yet we're they go to.

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[stutaeng]

Um, not sure what that's for. It's not connected to anything? The front-most connectors are the coolant level and MAF sensors, but those are routed though the firewall...

 

[98k2500]

Um, not sure what that's for. It's not connected to anything? The front-most connectors are the coolant level and MAF sensors, but those are routed though the firewall...

Nope, they were not connected to anything. Ill keep looking though. Has to go somewhere