Computer incomplete

Computer will not reset until the codes problems are fixed and stays off after the repairs.

Start with P0340 this is the cam sensor circuit, test wires to the PCM if ok replace sensor. It can cause P0300 misfires detected.

Just to add to this answer merlin2021 most of the time a code p0340 is caused by a black carbon building up on the plugs and wire's on this car. Changing the plug's and wire's usually fix's the code and is probably why there is a random miss fire code now. There is no cam sensor on the engine only a crank sensor. Also when saying the egr etc is incomplete are you talking about the monitor's not setting?If so after you get all the code's to clear and not come back drive the car for 50 mile's on city and highway driving without turning the key off and that will usually set the monitor's on that car.

Here's the scoop on the P0340 you need to check it this way:
Circuit Description

The Electronic Ignition (EI) module supplies a signal to the PCM whenever it determines that
cylinder No. 4 fired on its compression stroke. Because of opposite coil tower polarity, the
simultaneous firing of cylinders No. 1 and 4 are of opposite polarity as well. Under the most
conditions, the waste spark cylinder fires before the compression cylinder in sequence. The EI
module can determine this polarity sequence and voltage amplitude by using capacitive pickup plates
located under cylinders No. 1 and No. 4 coil. If module senses a positive and negative sequence and
high negative spike when cylinder No. 4 is on TDC, it pulls the PCM cam signal to ground signaling
that cylinder No. 4 has just fired on compression. This signal along with the double pulse received
from the CKP sensor, synchronizes spark and fuel timing.
DTC will set if the PCM voltage on cylinder No. 4 signal wire is not pulled to ground (cam signal
pulse) when engine has been cranking for 5-10 seconds or when engine is running. Cam signal is
continuously checked when crankshaft sensor pulses are received by the PCM, except under
deceleration.
Diagnostic Procedures

1. Connect scan tool. Start and operate engine for one minute. Using scan tool, check if DTC is
active. If DTC is active, go to next step. If DTC is not active, problem is intermittent. See
DIAGNOSTIC AIDS.
2. If engine misfire is present, check for a fault condition on cylinder No. 1 or No. 4. Check
wires, plugs and cylinder compression. If engine misfire is not present, go to next step.
3. Install a jumper wire between IC module terminal "D" and harness connector. With engine
running, observe 7X counter by using test light. Connect test light to ground and momentarily
touch jumper wire. Observe 7X counter on scan tool. If 7X counter resets to zero when touched
by test light, check tightness of harness connector terminal to EI module or faulty EI module. If
7X counter does not reset to zero, go to next step.
4. Check cylinder No. 4 signal circuit between PCM and IC module terminal "D" for open, short
to ground or short to voltage. Repair as necessary. If circuit is okay, check tightness of harness
connector terminals to PCM.
Diagnostic Aids

When attempting to diagnose an intermittent problem, use scan tool to review malfunction history
information. This data can be used to duplicate a problem.

By the way Autozone can test the EI module for you, and they do it free.

Also I think around your year, Saturn had an issue with NO starts due to fualty Crank sensors, seems when hot they were temp sensitive.

Yes from about 1997 and up on the S model they were known for failing crank sensors causing no start's and were heat sensitive when they were failing. As far as testing the module at auto zone they can test it but the problem I have seen is they tend to fail when they get heated up and will test good when cool just like a starter etc will do. Also new there kinda pricey to take a guess at so what I do when I suspect it could be a bad module I pop on a used module and see if that fixes the problem. You could pick one up at pick a part. It's not a high failure part from what I have seen I have replaced more coil's then module's on that model saturn.