Starting in limp mode

Masterblaster

New member
Jun 17, 2026
1
0
1
Illinois
Hello fellow LB7 owners,

I have an 03 2500HD with 266K that is starting in limp mode. Batteries and alternator are new and tested. CP3 pump has pressure. Fass pump is working and is a little over a year old. Every morning when I go to start it will start in limp mode. If I shut her off, open and close the door, a lock it, wait for the dome lights to dim, unlock it and act like I’m getting back in and start she fires up normal (most of the time). Thought the fuse box was corroded but it’s nice and clean underneath. Has anyone ever experienced this? I’m at my wits end with this. When she starts she runs perfectly. No loss of power, no smoke. It’s strange
 

2004LB7

Super Moderator
Staff member
Dec 15, 2010
8,597
3,094
113
Norcal
Welcome

Limp mode will always have a code associated with it unless it's been tuned and codes turned off without dealing with the reason for limp

Get us a code and we can help you. There is at least a dozen reasons it can go into limp mode. So we need the code