Short story plug-in scanner it lights up and says cannot communicate make sure the key the is on and it is
longer story car was given to me because the block was broke where the starter bolts up low mileage car excellent condition about 50,000 miles it's a 2000 model Vortec 4.3 space 6 cylinder the wiring was completely removed computer taken out battery out engine and transmission out parts put in good used block and everything reassembled when started battery light did not go out and I had a check engine light went to put scanner on and no communication with computer have checked cigarette lighter fuse and it is good any help on how to establish connection so I could read the codes would be greatly appreciated note when I say wiring removed I am referring to computer unplugged and kept in a dry spot and circuit breaker panel removed plus wiring to the engine and transmission this was all sprayed with electrical cleaner/conditioner before reassembly

 

If the scanner starts up and displays messages then you probably have a good power and ground at the ODBII connector. That leaves:

1. Scanner not capable for that year
2. Wrong scanner set up
3. The class 2 data bus is corrupted and the PCM data to the DLC has been impacted.
4. The PCM, its power or grounds are hosed

Probably the best place to start is the class 2 bus. You can locate the blade connector that puts everything on the bus and leave only the DLC and PCM. If you have a scope you can also look for a data stream.

George

 

i think it's #3 the battery light is on the gas gage dont work temp gage dont work engine light on also it starts and runs seem's good smooth but have not drove it yet . i see flashed computers online for $120 thanks for any help

 

Sometimes the class 2 data lines go down because one of the modules on that bus has failed. I would not buy a PCM until you take everything off the bus except the PCM and the DLC connector to see if the code reader can connect. It might be a module but not the main computer.

George

 

would that be the sp201 splice pack and where is it i have looked around the cosoul area and the left of the brake release this is a 2000 chevy blazer 2wd lt and had the engine out now wont connect to scanner, fuel gage, temp wont work and red battery light on . i really need help thanks PS. it runs and shifts great

 

Yes the splice pack and blade assembly is under the dash on the left side, this video shows a guy accessing it:



Every gauge except the oil pressure gets its data on that same class 2 data bus so the scanner problems and some of the gauge problems may have to do with that bus. If not then we need to look at the signal wires coming from those two sensors to the pcm.

What is your resting battery voltage and what is it when the truck is running?


George

 

the comb came out very easy when i opened sp201 i tried to scan with comb out it but it would not connect .

i did not try to start it but when i drove it the gadge said 14 volts even though red battery light was on

 

When you remove the comb it disconnects almost everything from the class 2 data bus and almost none of the modules can talk to each other. You will need to connect just the VCM/dark green (B) to DLC/purple (A) and see if you can connect the scanner. If you have a scope look for data traffic on the bus.

While your at the DLC measure the voltage between pins 16 and 5 and then 16 and 4 with key on.





George

 

thanks for the info george we are having a cold as hell front so no chance to try it all out but going to make a jumper wire set like on the video

 

i had some things stop me from working on my blazer today i had the comb out of splice block and jumped purple and dk green still no connection could i run a jumper wire from the computer to the data port