Codes 121 and 542
#1
Junior Member
Thread Starter
Join Date: Feb 2013
Location: Goldsboro, NC
Posts: 2
Likes: 0
Received 0 Likes
on
0 Posts
Codes 121 and 542
Well Im new here. I have a 1994 F150 5.0 auto. I've had it for about a year. Ive searched all over for this problem and can't find anything that helps me out. I've been having a problem with the truck idling low then jumping up. It will do this mainly when stopped. I used the jumper wire for the diagnostic test. I got 121 twice and 542 twice. Nothing for the continuous codes. Not sure what I did wrong here. I tried to look into the 542 code pcm to ground, but can't figure where to start. Any help would greatly appreciated.
#2
Senior Member
Start with the pmc to make sure the bolt on the pmc is not loose. Than there is about 5-7 ground wires though out the truck. Clean all ground wires. 121 could be the tps or bad ground also. Google your pmc,year,model and engine size. It has 3-5 pins in it that go to ground.