First Post...Awesome Forum!

[markinnh]

Hello,

Have a 89 K3500 350 TBI. I am sure the knock sensor wiring is melted...we use this as a plow/sander and last year the manifolds back to the mufflers were cherry red many times over....its an awesome snow moving machine!...if we only had a nickel for each ton of snow this baby has shrugged off! But I digress...heres the question, i can follow the wiring diagrams in my dare I say haynes manual to get the wiring back for the knock sensor, but the book shows the auto timing sensor unit that i must unplug, on the firewall. I cannot locate it on the firewall, i have read here that it is sometimes inside the cab, but where is it ???

Any help would be huge at this point. We are trying to eeeeak one more season out of the old girl and could use a little help.

Thanks

[bracketshark]

It should be a light brown wire with a black stripe located under the black plastic cover, nearer the distributor than the Passenger fender,it is on the firewall . I have a 94 pickup and its located under the glove box inside the cab, it can be acessed without dismantaling the glove box. I changed a motor in a 93 suburban once and this wire was located under the passenger side seat just under the carpet. Its a small wire and connector. Good luck

[markinnh]

The wire and connector is NOT on the firewall. There is NO relay cover like on our other chevys of this era. There are what look like two fuel pump relays, one of which is not plugged in (unknown) we are getting voltage from the knock sensor at the ecm, could this be a connector laying on the manifold?...i do not see the wire in the schematic in a (haynes) manual. Is there any online resource for more accurate schematics?

If I am getting voltage from the knock sensor, does this mean that the wire is connected? I do not see a specific input on the ECM for this timing sensor i am looking for.

[J-Ri]

Check inside like bracketshark said, they can really be anywhere. The connectors are all over the place. I think the guy on the assembly line had lots of extra wire and was looking to get revenge on mechanics. As long as it's a light brown wire with a black stripe, I would try unpluging it wherever you find it. If you can't find it, you might end up having to cut the wire where it comes out of the ECM and put your own connector in.

[markinnh]

Hey Folks Im Baaaaack!
still stumped on this truck. found the wire...it had been cut and butt connected near the PCM...cut it again, no change in the timing...still on 0 degrees, connected....still on zero degrees...signal is coming from ESC module....we did find a semi crushed braided fuel line...could this cause the flatness/no power issue?....also it has been suggested that there is a squirrels nest in the muffler....hmmm also no codes are set but what does it mean when with key on, without entering code read mode(blinks 12 (one...then 2) if the serv eng soon light blinks very fast? like once a second...i can enter code read mode and get my three rounds of 12 then nothing....any ideas?...is this a telltale sign of a bad ground or?