Problem with my 1997 Oldsmobile Aurora 4.0.The
service engine soon light is on. Sometimes it turns
off but only for about 5 miles and then comes on
again. I used a computer reader and I found 4
codes :P0404 P0300 P1645 and P0404 again.
I put an injector cleaner in my fuel and now I'm
thinking to replace the EGR valve. Do you think that
is going to solve my problem or what else should I
do?I'm also running out of time because in about 2
weeks I have to do the emission test on my car.I
would really appreciate your advice. Thank you.
OK, lets go one at a time. First check ALL fuses
underhood and in the fuse block under the rear
seat. P0300 misfire. Need to find out which
cylinder. You need to see live data for that. A code
reader cannot do that. 4.0l v8 are well know for
corroded ignition coil towers. Just pull plug wires off
coils one at a time and look for corrosion on coil and

Also could be a burned plug wire at the spark plug.
The ones in the back are usually the culprit. P0404
is EGR pintle open position error. The
pcm(computer) is not seeing the correct feedback
position. Either egr is bad, or just full of carbon.
Could try to remove valve, tap on the ground to
clean out any carbon. Or use compressed air. Since
it came up twice, sounds like it is current and
history code.

P1645 is the evap system purge control valve
circuit. Possible bad solenoid, or connection
problem. If you can use a volt/ohm meter, check for
12 volts at pink wire to make sure you have correct
voltage in.

The problem is; how long have these or some been
there, or did they all come at the same time. If
happened after radiator replacement, then would
suspect a harness got moved or pulled causing a
loose connection. Aside from all these things, some
normal places of poor connection/broken wires is
the harness going into the firewall below and toward
the pass. side of the master cylinder.

Clear all codes and grab and move that and other
harness to see if that causes the light to come on.
The egr wires, evap. Solenoid wires, and injector
wires all go in that harness and travel under the
throttle body. It is possible that these are all or
some related. That was a common problem area.

If you are familiar with auto repair, could do some of
these things yourself, if not, would suggest a good
repair facility, since there are several things,
different systems having problems. Over the years
have had any one of these parts go bad (egr valve,
purge solenoid, coils, wires, plugs, injectors)Let me
know if i can be of more assistance.
1997 Oldsmobile Aurora P0404, P0300 And P1645

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