Pcm not communicating

[Ethan Teeters]

So I bought another mustang as a project... it's a 1999 v6 5-speed ford mustang. The car will crank but won't start. Also the fuel pump doesn't kick on. Theft light is flashing, and the pcm is not wanting to communicate to a snap on tablet. I first began to replace the fuel pump and filter, and nothing still didn't work.
Then I found out that the theft light was flashing. I had someone come out with a snap on tablet and we got a new key and started setting it up. But the pcm was not communicating with the tablet. So i went and got a brand new pcm for the car, installed it and it started to communicate.I ended up manually hooking the fuel pump up to a battery. To fix the fuel pump not kicking on. I Turned the key on and the fuel pump started working. The car started right up with the fuel pump manually connected to a battery and a brand new pcm. Turned car off and the pcm stopped communicating. Even kept the fuel pump hooked up to the battery but it wouldn't start. The theft light turned back on. I'm really stuck on what to do, I'm 17 and i only know so much. Please help

 

[alwayshi]

I had a similar problem to this recently. Ended up being a bad CCRM. I’ll find the thread for you to sift through. Burns helped me diagnose and check a lot of stuff.
So before I post the thread. Check your fuses if not done so. And by check, I mean pull and literally check each one, then check for continuity and/or power

 

[alwayshi]

Electrical - CCRM / Inertia switch / something else?

Hello everyone, I currently have a 2000 GT 4.8L that I just supercharged. Car has been idling and running fine before the supercharger, and including now (as of right now I'm datalogging, no full pulls, staying out of boost). Today, my tuner came to make some adjustments and I started the car...

www.stangnet.com

 

[wmburns]

Please understand there are several "conditions" that could cause your reported symptoms. The first recommendation I would like to give is to resist the urge to "part change" to a solution. Instead, perform some targeted tests and go where the results led.

Go though the "crank with no start" check list. Pay attention to what the check engine light is supposed to do during cranking. Pay attention to exactly what the theft light is supposed to do. Again, understand that a PCM power/ground problem can CAUSE an apparent anti-theft (PATS) problem.

Also note the role that fuses F2.34, F2.2, and F2.8 can play in this. Confirming the power state of these key fuses would put you way down the road to understanding where the problem really is.

Crank with no start check list:

1997 mustang wont ignite

Hello lets start with I have a 97 mustang gt v8 standard I had new engine transmission ect put all new well last month i shut the car off and had no power at all bought a new battery and alternator got all power back but it wont ignite brought to mechnic for a month all sensors codes ect are fine

www.allfordmustangs.com

 

[FoxBodyChris]

I have the same exact issue with mine. I drove the car for three years every day not one issue. I put a Holly term x and on3 turbo on for a summer and decided to go back to stock this summer and now I got all ————- on my odometer no communication to pcm and fan runs low with key on. I installed new pump and just got a new ccrm because of people saying that was the problem. I checked all the fuses and connections at ccrm, inertia switch and pump. All get power. If I dump gas into the intake and it will fire but have no injection pulse I guess. I’m ready to just stop waisting money and get the edelbrock carb intake and MSD mod 6 ignition kit. And rip all the ecu’s CPU’s gpu’s, ccrm, pump driver out