ohyeahcrx

Ok so my truck is throwing some codes. 51 and 52. 51 is TPS and 52 is knock sensor. My truck has also been having issues, when i revv up past 2k RPM check engine light comes on and it runs really crappy. So I did some research and found out that some guy was having the EXACT same problem and the solution was his knocksensor wasn't in all the way. So he tightened it up and it fixed the problem. So I decided to try that. I know the knock sensor is around the fuel filter so thats where I start. But im not exactly sure what it looks like. But in my search for the KS I come across this sensor thats to the right of the fuel filter, with what looks like a 3 wires in a flat line comming out of it. I follow it down and see that its been cut. So what sensor thing is that?

It is approx. to the right of the fuel filter would go. The thing with the white plug in it. (Not my engine. cant get a pic cause of all the intake mani stuff in the way.



Sorry its so long but help!!!

bipolarandproud

Mine has 1 wire for the knock sensor .
I believe this is it .

ohyeahcrx

Ahh thats the knock sensor? Does the wire connect to a cluster of them that roughly goes under the intake mani, then get put in a large wire loom? Cause i believe that that is cut aswell.. its hard to tell where everything goes to because theres alot in the way. ill try and take a picture.

bipolarandproud

I'll try to find you a picture.

bipolarandproud

Yeah it does go to a cluster of wires .including the fuel injector wires , temp. sensor ,tps wires etc .all in one harness .

ohyeahcrx

Thats the best I can get of one of the cut wires and the knock sensor. I relize now that the top one is the knock sensor and i kept trying to get the bottom one in the picture. ha dang.

muddpigg

iTrader: (1)

for the tps pull and check resistance. http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml . check timing if tightening knock sensor doesn't work. I used a hammer, vise, and multimeter to check knock sensor but some say that method don't work. I got a value change so deemed it worked.

bipolarandproud

That looks like the one .Reach your fingers on the knock sensor the little plug in thing might still be on there. The wire could have been pulled loose from it . It unclips from the sensor IF it's there , Then your can solider it back on . I've had to do mine plug like that it's one copper wire with some kind of silver looking insulated wire around it .

bipolarandproud

Good looking out Muddpigg I forgot to get to that .lol

ohyeahcrx

Ok cool thanks guys!!

Ill check them out tomorrow and see if those work and what not. Ill be sure to keep you updated!

bipolarandproud

Ok bro ,I hope you figure it out .

ohyeahcrx

Alright so heres the situation.

One of the cut wires is not cut, it has come out completly from the clip that clips in to the knock sensor. heres a poopie diagram

///////// 0000 ____________
\\\\\\\\\ 0000


////////
\\\\\\\\ = Knock sensor

0000
0000 =clip that goes in to the KS

________=wire that is no longer connected to the clip at all

The wire looks like it was ripped right out of the KS clip. can i just stick it back in or what..

abecedarian

The knock sensor wire should be a 2-wire conductor that looks sort of like cable tv coax- one center wire and another braided shield wrapped around it- to a single wire plug. The shield should be grounded somewhere back by the firewall so make sure that you don't accidentally connect the shield to the center conductor as that can cause the 52 as well.

As for the 51- it has 3 meanings: TPS IDL contacts open, A/C switch is on or neutral safety switch is engaged when diagnostic jumper is inserted.

muddpigg

iTrader: (1)

mine's a single wire, but also an '86 so my codes are different and maybe ya'll got the coax wire.

ohyeahcrx

FIXED!!
No more knock sensor code!! Yippie! haha
I just more or less re built the plug. since it didnt have a wire coming out of it i semi took it apart, put one in there, and connected it to the wire that was cut and bam no more code 52!!

Now time to focus on 51.
That link muddpigg posted, I can check that with the TPS still connected to the TB and everything right? I think I have a tester thing, so hopefully ill do that later today.

and for the A/C switch do you mean on the climate control, everything is off?

muddpigg

iTrader: (1)

Rock on. Don't know if you will accuratelly (sp?) check it on rig.

ohyeahcrx

Realy? Cause ive heard that its bad to take it off. Is that true or just lies? haha

abecedarian

One thing I've done a few times when playing with the throttle position sensor, is loosen the two screws and slowly turn the top of the sensor towards the rear of the vehicle while listening for a sudden idle change. If I don't hear one, I rotate it back towards the radiator and listen for the idle to change. Once I hear it drop, I snug the screws down enough to hold it in place but loose enough that I then tap it back and forth without it moving large amounts. Then I tap it to get just slightly past the spot where it just lowers the idle when it's tapped it forward. Then I tighten the screws up, pull the efi fuse for a minute or two then start it and see how it goes.

muddpigg

iTrader: (1)

Oh your right you don't need to remove to check resistance values, but think I pulled the whole thottle body and gave it a cleaning at same time. But the trick Abe above mentioned would help if you did. But probable won't help you 2000rpm issue, but measuring resistance should help to eliminate it as the cuase of your issue.

I'd bet its a high vacuum switch/line leak or an EGR issue. But don't get ahead of yourself. Vacuum issue may be why the AC code is being thrown too. Keep troubleshooting, we all might learn something

ohyeahcrx

Ahh yes. The knock sensor issue is what was causing the run like poop after 2000 rpm. So now it runs fine (even though when i did drive it it wasnt a long drive or anything, just like around the block.) but after a while of driving the check engine light came on. I checked the code and it was 51 (TPS) but when the check engine light came on there was no change in how the truck drove or anything. Normally is there some kind of difference that is felt when the EGR or something is the issue? (granted if its the A/C switch i know I wouldnt feel a differnce haha)