Well, to begin with, mechanical and clogging issues with an injector will not throw a code, so you're definitely dealing with the electrical side. The first thing I'd do, assuming no test equipment, is to see if I could isolate the problem.
Step one in this is to check which kind of injector connectors you have. If you have the type with a wire bale to hold them tight, it is difficult to pull the connectors, so it helps either to remove the wires temporarily, or at least to practice pulling them before you do the test.
Step two is to get the engine running at idle, if it can. Now pull one injector, and observe what happens. The engine management system is pretty good on maintaining idle speed. If the injector was working, the engine will bog slightly, then recover. If the injector was not working, there will be no change in idle speed. Between tests, reconnect the injector and give the engine a little throttle to burn off any unburned fuel before testing the next one.
Once you've done all 6, you should now know which injector is not firing. I'll assume for the moment that it's only one. Now, with engine off, swap the connection from that injector with its nearest working neighbor. Restart the engine, and repeat the test. If the same injector as before fails the test, you know the problem is with the injector. If the failure follows the harness, then you know the problem is with the harness.
Your job now is to trace the defect in the harness, or to replace the faulty injector. I've had (and heard of others) problems with the +12 volt supply to the injectors. This is a steady +12 that is fed to the injectors whenever the ignition is on. The injectors are switched on and off on the negative side by the PCU. The +12 is distributed through a series of splices in the harness, and a bad splice can cause this problem. So can a bad connection or corroded pin on the PCU. A good multimeter can help a lot with this.
If the problem is with the +12 in the harness, you can bypass the bad part by going into the harness further back, splicing in another piece of wire, and jumping over the bad splice.
