Question = the fist code was bank 1 running to lean changed plugs wires now this code comes up mass circuit voltage low what could that be.
JK: You could have a vacuum leak. Suggest checking for that First next, check all fuses, then check the wires at the MAF sensor connector. Sometimes they break inside the colored insulation. Pull slightly on each wire at the connector. If a wire is broken, then the insulation will stretch. This will give the P0102, which may also have given the lean code.
1998 Pontiac Bonneville SSE. Engine size: 3.8 L. Check engine light. Code P0300 cylinder 6 misfire. Replaced Fuel filter, fuel injector, spark plugs, spark plug wires, upper and lower intake manifold gaskets, ignition coil pack, ignition control module. What else could be making that cylinder misfire?
With all the parts replaced I have to say that this is not an ignition problem. You need to find out if the PCM (powertrain control module) is actually controlling the fuel injector allowing it to fire. Each field injector has one wire that is hot with the key on at all times, usually a pink wire, and the other wire is what the PCM uses to ground the fuel injector. There is a special injector test light called a "noid" light. You can also use a normal test light. If the PCM is controlling the injector, then I would have to suspect it is an internal engine problem. Possibly a broken valve spring or bent Pushrods. If there is any engine noise around the cylinder that is misfiring then that would suggest a mechanical problem as I just mentioned. If there is engine noise on that cylinder, remove the valve cover and inspect the rocker arm for being loose. You may also want to do a compression check before you do that.
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