Toyota Repair: No Communication with scan tool

Question
QUESTION: Hi

I have a 1998 Toyota Celica Gt, 2.2 L ...time for the emission test.
Took it there and they couldnt communicate with the computer.Stopped at 2 different Autozone to verify and neither one could communicate with the PCM.
Fuses are all OK. Check Engine light does work with bulb check but not on while running.Vehicle for the most part runs and starts fine....only on 3 occasions ,right after start up it will run a bit rough and wont clear out with acceleration but if i shut it off and immediately restart it, it idles fine.
What are the next steps to checking the DLC to get it to communicate
thanks in advance
Joe

ANSWER: Hello, check the pin connections at the DLC, make sure there are no broken wires at the back, look for damaged pin sockets, use a test light and check to see if at least one terminal has voltage with the key on, it comes from the computer, you could also have a  faulty computer due to the issue with the check engine light not turning on when the key is on, access the computer, it should be under the glove box or the right kick panel, check the computer connectors also for corrosion or bad contacts.  

---------- FOLLOW-UP ----------

QUESTION: Hi Ted,
Thanks for the fast response. I must've not made myself clear .
The check engine light works fine,meaning it comes on with key on  and/ or start up then goes out once running.

I did check connector, i pushed wires in from the back of the DLC and now i can communicate with the scan tool.Thanks you!!

Now my other symptom i need your assistance with ,if you can.

The concern is , intermittently, i'll start the car, starts up fine, but it will run rough and if i try to clear it out with acceleration, it wont'..just sits there and kinda sputters/runs rough.......but if i shut the ignition off and immediately restart it, its fine,runs smooth and accelerates well.
It may do it once and not occur again for 2 weeks,then may do it 2 days in a row and not again for a week or 2.
It does have new spark plugs, cap , rotor and wires.
There aren't any codes stored in the computer.
Any idea what may be causing this ?

Thanks in advance

Joe

Answer
It's hard to say what causes an intermittent condition like this, try replacing the coolant temperature sensor for the computer, there are two sensors one for the gage and one for the computer, it has a connector with two wires on it, both are located at the end of the cylinder head.