4l80e limp mode bypass. I just finished a 2 year rebuild and took the Humvee for a test drive after getting it registered. I have an 87 chevy V20 with the 350 and swapped my TH400 for a 4l80E and used the E-Z TCU transmission controller and it worked fine for a small while and now I can start it and it works fine and then after a short time of use it goes into limp mode and wont come out till I turn it off. Chevy Forums FREE technical assistance for your restoration and repair. Hi having a intermittent problem with my 4L80E dropping into limp mode. I bought the truck non-running / not driving. If you're getting reduced engine power, car can't go fast The smog technician accidentally triggered limp mode on my beast ( 1995 suburban k1500 ) by not reconnecting the ECM wire (located under passenger side glove box). It will shift 1-2 then go into limp mode when it trys for 3rd. The reason I bring this up is I now have a 98 k2500. 0 4L80e np246 with a supposed good 4l80e (1997) w/torque converter, and it appears to be stuck in limp mode. Once Limp Mode engages, the engine will only run at very low rmore The official GM 4l80e book/PDF has amazing (and overwhelming) detail. 7hb1, qlcc, nsdke, jhwy, 1x9gc, c1gv, c4va, pn3v, ziqbwd, uyimh,