You need to be able to see what your PCM thinks is going on. If your scanners won't communicate with the PCM...... That is where I would be looking.

 

your OBD2 link should have power going to it, not sure which pin off the top of my head, but if it doesn't have power, your scanner won't work. Check into that before you go swappin computers....butttt, if you're havin all the problems you are it could still be a PCM issue

edit: Pin 16, which should be a pink wire, should be your hot wire. It draws power through fuse #17 in the fuse panel inside. I got this info from a 97 wiring diagram so should be right...

found a pic of the connector to help show the pinout... this is from a camry I believe but it'll do the trick here...

 

Ok, so I have 12V at pin 16 and Ground at pin 4. There is NO wire going to the back of pin 2. What am I looking for at pin 5 exactly? I checked it for power and ground and it has neither. The OBDII scanner does power up however gets a link error when it tries to connect to the pcm.

This all started when my old battery was dead. The truck labored when starting however once running it was fine. After jump starting the vehicle this all occurred. Now there is a serious draw on the new replacement battery. On a full charge it will be dead next morning. No lights are on and I cannot see anything running to indicate the draw.


Does anybody have a diagram for the 98's PCM? I am getting power to the PCM and the OBDII port however still no link on scanner and no spark or fuel. The thing that has me stumped on top of the no spark or fuel is the constantly draining battery. Thanks

 

I just posted that pic to show where the power was on the pin.... the pins might be different for our trucks but my diagram showed pin 16 was hot.... Gimme a second I'll see if I have a diagram for the pcm

 

Oh ok, Thank you for helping. I appreciate it.

 

Ok try this.... I've never uploaded a pdf document before so if it doesn't work I can email it to ya....



https://docs.google.com/fileview?id=...ODczMmUw&hl=en


I got this from another member here, Diefenbaker, so credit goes to him for actually finding this lol...

If you have power at pin 16 then that takes my idea out of the mix.... maybe you do have a bad pcm... hope not though

 

Thank you very much. That is a great set of diagrams. I am more lost now than ever lol. This is one of those times I wish I had a friend with the same truck to swap PCM's. Any more troubleshooting ideas before I dish out the cash on the PCM? Thanks again

 

Any ideas? I checked all grounds to PCM as well as power leads. I noticed one thing that seemed odd. With plug 1 removed from the PCM I was able to see ground at pins 31 and 32 however notice that I had connection between pin 22 and 31/32. I show 22 as a 12v lead. Would this make sense or does that show that something in the PCM went bad? Thanks guys

 

i am having problems with my 98 1500 5.9 4x4 i changed the passenger side exhaust gasket and lost spark the truck started up after i changed it and then i shut it off and lost spark i have changed the coil , crank sensor and the plate under the dis cap still nothing i have checked fuses all are good when i turn the key on everything works fine the FP turns on all the gauges work just no spark any ideas please help randykottwitz@yahoo.com thanks

 

If the computer isn't sending a ground reference to trigger the coil it won't fire. Did you check to see that you have voltage to the coil when keyed ON. The other thing is wether or not the injectors are firing,because if the injectors and coil are not firing,then the ASD relay could be bad.The injectors and coil positive have the same power feed.