Cascade Crew

Wolffy · Member Joined: 22 Jan 2004 Posts: 375 Location: Spokane

i put a new motor & tranny in my 95 tahoe & am now getting that error
i disconnected the battery to clear it already & got it again
i was getting a 2nd error code saying the timing was in error, but that was prolly from when i first started it & it was out & now set correctly & no more code for that
before the new motor/tranny i wasnt getting any error codes
any ideas/suggestions?
from what i can find so far the ESF might also be the knock sensor?
thanxs

EDIT all new tune-up parts installed
the gas is about 6 months old, gonna put in injector cleaner & fill the tank tommorow & see if that helps

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

Yes, that code is for the knock sensor. Knock sensors have a torque spec, I would suggest re-torquing it before replacing it.

check resistance of knock sensor from knock sensor to the engine block as a ground. It should be about 3.9K ohms. If it is less than 1.5k ohms, or more than 10k ohms replace sensor, it is bad.

Did you put same size motor in as before, btw? What about PCM?

Wolffy · Member Joined: 22 Jan 2004 Posts: 375 Location: Spokane

yup same size motor
diff year block & of course bore size, thats it

What about PCM? whats that?

Wolffy · Member Joined: 22 Jan 2004 Posts: 375 Location: Spokane

i had a thought last night, yeah kinda scary for me too, lol
i wondered if the knock sensor on the original motor was used or not, so i looked and there was still 1 on it, not sure if it got switched over or not (a friend helped me, not sure if he maybe did it, cause i didnt, im gonna check w/ him today)
if it wasnt, then maybe the one on the motor is bad

Sellmanb · Member Joined: 30 Nov 2004 Posts: 727 Location: Tigard, OR

I would suggest switching to the original knock sensor that you know works. From what I can tell, knock sensors are pretty ECM/PCM specific. ECM/PCM are essentially the engine's computer.

blue89 · Posted: Thu Oct 11, 2007 7:45 am Post subject:

I'm pretty sure the vortec and LT1 are the same computer. If they are, the knock sensors are funny. The LT1 knock sensor has an actual sensor in the block, but then a module in the PCM. You can get an updated LT4 knock module that goes in the PCM that is less sensitive to normal engine noises. I guess its a common swap. I'm thinking about doing it to my LT1 since I get knock counts when it shifts gears (wtf). I also have a 97 Vortec 350 Tahoe so I have some interest in this thread.

And to correct the ECM/PCM thing. The ECM is the Engine Control Module. It controls just the engine. The PCM is a Powertrain Control Module. It controls the engine and tranny. If its an auto tranny tahoe it has the 4L60E or 4L80E which are controlled by the PCM. It controls hydrolic pressure, up/down shift points, and the amount of time it takes to shift. Shift points are set by MPH, so if you change tire sizes or rear end ratio's, your tranny will shift differently. Make sure you have the PCM adjusted if you've changed any of that.

Wolffy · Member Joined: 22 Jan 2004 Posts: 375 Location: Spokane

thanxs good information to know about tire size changing the PCM
but my tires are stock size
and my 95 tahoe isnt vortec, that didnt come out till 96

blue89 · Posted: Fri Oct 12, 2007 6:13 am Post subject:

what engine and computer is in it?

Wolffy · Member Joined: 22 Jan 2004 Posts: 375 Location: Spokane

i checked & the Knock sensors were diff part #'s
so i put the old one back in, cleared the comp & all is good now