98 Buick Lesabre p0203 p0303

I bought a 98 Buick LeSabre Limited about 2 weeks ago from the original owner it ran great with 124,000 miles no problems very clean. Now suddenly i get a miss and get 2 codes P0303 and P0203. i changed the plugs and wires because they looked to be originals. The Injector was inexpensive so i went and replaced that, it didn't help anything. After doing all that i went and listened with a scope and screw driver on the injector i noticed its not firing, so i disconnected the injector and used that cyc 3 plug on my cyc 5 and it wouldn't let that injector fire either. so i know that's its not getting the signal to fire. the cyc 3 plug is getting voltage but it doesn't go up or down with it running. I've read conflicting stuff saying it could be the cam position sensor or the PCM. I'm at a road block and not sure what to do, I'd rather not keeping changing stuff till i finally figure it out so i found this nice site and would appreciate any ideas on my problem. thanks to any and all who can help me.

I'd doubt pcm for the reason that it's contained to just one injector driver circuit. It is possible but on tht car I'd be more prone to expect a wiring issue then single driver failure in the pcm.

If the wire or "circuit" is good from the injector to the pcm is good then the pcm is bad. The new PCM MAY have to be programed before the car will start if this turns out to be the problem.

It was weird because it was working then the next day it had the problem right away. How should i check the circuit from the PCM to the injector. Are there any diagrams on the PCM so i can identify the correct wires. Also how do i program a new PCM? or should i just get a junk yard PCM that works for that car.

got this from a servicing GMs 3800 site "If an injector reads good, use a noid light to check for an injector pulse from the PCM injector driver circuit. No pulse? The problem could be a bad injector driver circuit in the PCM, or no input from the camshaft position sensor (CMP), which the PCM uses to fire the injectors. The CMP sensor is mounted on the front timing cover. "

If it was a cam sensor you would not have the P0203, This codes sets because the PCM saw a open/shorted condition on this injector circuit. Also if the noid light does not light this does not mean that the injector is bad it means that you are not getting power and or ground to this injector. The wire color should be GRN/BLk and at the pcm the blue connector pin 73. The PCM will have to be programmed by the dealer or someone with a dealer level scan tool and access to the gm website.

If you're checking the wires for continuity and or resistance and it's still leading to a bad pcm take it to a dealer and get it properly diagnosed. I've seen noid lights not flash because of high resistance in the circuit after a continuity test says the circuit was complete. Complete but unable to flow the current required to fire the injector. Pretty easy test with a scan tool that will actuate the injector. If you don't know how to test it, read a wiring diagram, use a dvom or a noid light etc then get it diagnosed before wasting money on a pcm.