Here's a great step by step I just found: Part 1 -Engine Coolant Temp (ECT) Sensor TEST. P0117, P0118 (4.3L, 5.0L, 5.7L)

 

Occam's Hammer

The PCM sources the 5 v reference. You replaced the PCM, results the same
I'd be looking at your meter. Or the PCM grounds.

It's sort of unclear to me but you seem to be getting 10 v to chassis grd on both leads. Really cant happen unless the problem is localized to one part of pcmm and having some training in the type of circuit used.. cant see it even then. esp on two different units.

I dont have diags available but I'd check the 5v ref on different sensor ckt. One that isnt throwing codes.

 

PETTYFOG: well seemed weird to me too ive read all over that 5volts is sent to the sensor from the PCM i will later check other sensors
i do have a cheaper meter buy reads just fine tested on the battery and some outlets
my other thought was grounds too since i had one big flat metal ground undone coming from back behing my motor next to distributor didnt know exactly where it came from so i grounded it

the way i test it was directly from the diagnostics chart from this site posted by skylark
funny thing was didnt get any voltage reading when bridge both prongs and put my test leads on the wires right directly next to the prongs???????
did get 10+volts on the other testings.
so my question is??? how and where is the PCM grounded
thanks guys for all help and advice hope it is helping others

 

awesome article for anyone who has any of these two codes click on this, great step by step instructions and specific details. Just for noobies like me lol

thanks smitty looked everywhere for something like this
peace, love, and chicken grease

 

alright broke down and bought a actron CP9575 auto scanner OBDII with live data read.

ok i scanned my vehicle in steps and will give detailed ways how i did this because im new to this scanner and what info it gives me.
just note- have drove the vehicle for about 2 hours around town.... after sitting for about 3 hours i did these test)

the first scan was: I/M moinitor and this was done with key on only
misifre monitor....ok
fuel system....ok
catalyst monitor... inc
evap system... inc
sec air system... ok
a/c refrig... ok
oxygen sens... inc
oxygen sens htr... inc
EGR system.... inc

now this next scan is the live data/drive cycle monitor: with key on only
MIL status... on
ABSLT tps%... 0.0
Eng speed (RPM)... 0
calc load (%)... 0.8
MAF(LB/M)... 0.25
MAP(hg)... 28.6
coolant(*F)... -40
IAT(*F)... 91
IGN ADV(0)... 0
ST FTRM1 (%)... 0
LT FTRM1(%)... 0
ST FTRM2(%)... 0
LT FTRM2(%)... 0
fuel system1... open
fuel system2... open
02s12(v)... (.270)
02s13(v)... (.355)
02s12(v)... (.285)
ST FTRM21(%).... 0
OBD2 stat... ca

the next scan is the again the live DATA/DRIVE CYCLE MONITOR engine on only:
MIL status... on
ABSLT tps%... 0.0
Eng speed (RPM)... (600/851) dropped from 851 warming up
calc load (%)... (2.5)
MAF(LB/M)... (.70/.71) fluctuates between these two numbers
MAP(hg)... (0.6
coolant(*F)... -40
IAT(*F)... 86
IGN ADV(0)... 0(-19.0/22.5) fluctuates between these two numbers
ST FTRM1 (%)... (-1.6/.8) fluctuates
LT FTRM1(%)... (-3.1)
ST FTRM2(%)... (-2.3/2.3)fluctuates
LT FTRM2(%)... (-3.1)
fuel system1... closed
fuel system2... closed
02s12(v)... (.170/345)fluctuates
02s13(v)... (.290/660)fluctuates
02s12(v)... (.120/865)fluctuates
ST FTRM21(%).... (-1.6/3.1) fluctuates
OBD2 stat... ca

this last scan was with the engine turned off but key still one

MIL status... on
ABSLT tps%... 0.0
Eng speed (RPM)... 0
calc load (%)... 0.8
MAF(LB/M)... 0.25
MAP(hg)... 28.3
coolant(*F)... -40
IAT(*F)... 73
IGN ADV(0)... 0
ST FTRM1 (%)... 0
LT FTRM1(%)... 0
ST FTRM2(%)... 0
LT FTRM2(%)... 0
fuel system1... open
fuel system2... open
02s12(v)... (.270/.260)dropped from .270
02s13(v)... (.355/.345)droped from .355
02s12(v)... (.100/.105) increased from .100
ST FTRM21(%)... 0
OBD2 stat... ca
I noticed that the coolant temp stayed the same which it shouldnt have.

on a side note: my temperature guage worked fine and increased to proper temperature and the vehicle did not move from its spot stayed in park with these test
so with this data can someone give me some pointers, i can do more test if needed
and the same codes are showing p0118 coolant high temp. and cyclinder misfire on 1 caused from my coolant code lol
thanks guys for any help

 

Have you tested the wiring yet? Or just flat out replaced it? Sounds like it is shorted to a +12V source.

The gauge sending unit and the PCM sensor are two completely different devices on the motor. So the gauge working fine makes perfect sense.

 

. Like I mention in previous messages my wires tested good from the PCM to the connection no breaks

 

There is more to testing wiring than just continuity tests. Does the voltage persist even with the PCM disconnected? Is there continuity to the positive or negative battery post with the PCM & sensor disconnected?

Since you have replaced the sensor and the PCM, you really only have one other option for the source of the problem...the wiring (which includes the grounds). The wiring diagrams I posted earlier show the grounds and I believe give a general location. If not, post up the grounds (Gxxx) and I'm sure someone will be able to tell you where they are.

 

ive tested all wiring for continuity for my P0118 code to PCM and battery all good so my only option is the grounds for the PCM.
if anyone can help me find these that would be awesome
i dont have the time i like to check and double check these solutions bc of school and work
i have a 96 blazer 4.3 4wd
and have the letter W in my VIN (should tell you what engine i have in it)
again thanks for all the help from TN
nathaniel

 

well guys finally found my problem and i have to say it was a pain in my a** well with all the problems i now just have a misfire code probably from driving with the p0118 coolant code for several months, carbon build up, plugs, and wires need to be cleaned.... well i used 4 different sensors for the p0118 code and all did the same, light went off for couple of minutes and came back on well checked every wire from sensor to cmp and all good replaced the cmp and still same thing well the brands of sensors i used where from autozone and orielys i decided one day to by a delphi coolant sensor online, just a thought and wow to my surprise got rid of the terrible miss and bad MPG all my headache due to crappy "new" parts so guys anything dealing with sensor or electrical dont go cheap use what these guys say bc you can misjudge everything and end up in a hole.... my next task is to change hubs and ball joints got road noise and popping in front end with over 200 thousand on her and its original im sure it needs it thanks for all the help guys and advice and if anyone has any question feel free to message me peace, love, and chicken grease