Author Topic: 1986 gmc 6.0/4L80 oxygen sensor and trans codes??  (Read 600 times)

Offline 86charcoalsierra

  • Newbie
  • Posts: 19
1986 gmc 6.0/4L80 oxygen sensor and trans codes??
« on: April 10, 2020, 05:00:18 PM »
I have a 1986 GMC sierra I recently did a swap on from a 305 with turbo 400 to a 6.0/4L80 out of a 2002 Chevy Silverado 2500hd. this is the first swap I have done so I'm pretty new to this. I left the original harness on the 6.0 and just wired in the essentials to get it to run and drive no modifications were done to the harness except splicing in power wires ignition wires from the original 1986 harness. I'm using the fuse block out of the 2002 Silverado. I recently drove it around for about an hour and a half with a heavy foot. my coolant temperature stayed around 200 which is normal but my transmission temperature got up to 225 I'm thinking this is kind of high not dangerously high but I'm told it should run at about 175-200 is this true? I have a trans cooler in the radiator thinking of going with an external. what are yall transmission temperatures usually run on a nice sunny day? also, I am getting these codes p0706-trans range switch performance, p0753 1-2 shift solenoid control circuit, p0758 2-3 shift solenoid control circuit, and p1860 torque converter clutch solenoid control circuit. I'm wondering if I forgot to wire something in does anybody has any idea. truck runs good shifts smoothly but when I step on it doesn't feel like its downshifting it just goes instead of downshifting and then going.

I'm also getting oxygen sensor codes p0134 and p0154. I got the rear o2 sensors tuned out and I'm getting voltage to sensors. does anybody have a wiring diagram for the o2 sensors so I can check for ground and signal. or any idea what else might be causing these codes. thanks in advance for any help.

Offline JohnnyPopper

  • Site Supporters
  • Senior Member
  • ******
  • Posts: 1009
  • Old Goof
Re: 1986 gmc 6.0/4L80 oxygen sensor and trans codes??
« Reply #1 on: April 10, 2020, 05:34:32 PM »
Can't help with the codes, sorry.

About the heat, did you service the trans as in oil and filter? Overheating can be caused by poor circulation.

I bet you miss that quick 305... ::)
1957 Apache 3100 235 Inline 6, 3 on the tree
1973 C-20, 3+3 454 4BBL TH400  Water Injection
1978 K-10, 350 4BBL TH350 NP203 M.M. Part time Kit/Hubs
1980 C-10 under construction