helping a injujed friend get his car running, it fired up and ran kinda rough, and got to replacing plugs after scanning for p0300, multiple misfire, after the fun plug replacement, it wont stert, when cranking tach moves a bit, my generic scanner says no codes, but the auto enginuity cant select protocol, thinks ignition is off, when cranking ck engine light is on, security light goes out, so i got a wiring diagram of obd2 plug, and last circuit number 30 on c4 being tan, UART, was open to the number 9 obd pin, i ran a jumper wire, but still no pcm communication, can someone recommend something else im missing?

 

Did you check continuity across pin “E” in connector C105, and also pin “A12” in connector C200A/C200D. Those are the two harness connectors between the PCM pin 30 and the DLC pin 9. The factory service manual can show you where the connectors are located. Free download:

https://www.mediafire.com/?40mfgeoe4ctti

 

thanks for the link, i dont see anything in between that circuit on mine, do i use the 1996 firebird link?

 

I looked at the DLC wiring diagrams on Shoebox's LT1 site:

Scroll down for 96/97 DLC

http://shbox.com/1/DLC_wiring.jpg

The 1996 F-Body (Camaro/Firebird) factory service manual file is “1996-SvcMan-Bookmarked…..”. The 96 and 97 are 99+% identical.

The DLC for the LT1 is shown on page 8A-50-0 in the electrical section. The correct identification of the connector closest to the PCM is “C105”. I'll correct that in my post above.

C105 - “Behind RH wheel well and attached to PCM bracket” (see page 8A-201-15, figure 28)

C200A/B - “between LH kick panel and steering column” (see page 8A-201-25, figure 49)

 

pulled apart and checked continuity with c105 and c200, meter shows continuity, put them back together and showed good at dlc to pcm, ran scan again and still not showing anything, data stream shows baro and cts, cranks but no start, disconnected ebcm to see if maybe it was corrupting scan, no change, ill do the same with derm tomorrow also see if data is picking up crank rpm

 

If the tach moves up while cranking most likely the PCM is receiving the low resolution pulse signal from the Opti = RPM and crank position data.

Do you have spark? Do you have a noid light to check for injector firing while cranking?

 

after initial startup and missing, scanning multiple misfire, and changing plugs, everything went dead, i checked spark and injector activity, when i get back on it ill recheck again see where its at, update later today, thanks again

 

When it's cranking, is there any signs of cylinders firing, backfiring, coughing? Or total silence?

 

zero, when this surfaced i smelled fuel, but after rescanning and realizing something else was happening, went to check spark and fuel, i also rejoined 2 wires at pcm harness damaged by rodent, besides that and plugs, hasent run since.

 

well heres where im at, checked all injector pulse plugs, i got through one side dead, and when switching to driver side, i also checked coil for power, there was no spark because no power at pink wire, the module had power next to it, i didnt check crank sensor sharing same circuit, but added a jumper wire from module, in the meantime drivers rail had noid light flickering, in thinking i agrivated a connection mesing with everything, plugged coil in and car fired up, ran smoothly with new plugs, after 10 minutes of warm up, revved it 5 times and it stumbled and quit like it was starving for fuel pressure, i can hear pump on, next ill get a pressure gauge see whats up, also dlc is still not active???

 

Sounds like it may a problem with splice “S107” in the harness from Ignition Fuse 11. Or the “jumper” came loose.

And both the pink wire for the ignition and the pink wire for the injectors passes through “C100”.