My brother'* Bonneville threw a "SES" light today so I pulled the codes for him. The codes were 43 (spark misfire) 34, (MAF sensor wires loose( I think this code was set when it was unplugged for a second to make sure the connection was good)) code 66&67 (can't find any matching descriptions for these.)

I'm not sure what is wrong with the car. The light only turns on once and a while though. The car does run rough at idle at times. If the engine is revved in neutral when the engine is hot then you let off, the RPMs will drop to around 800 and the engine will start to missfire. The RPMS will fluctuate rapidly from 800 RPM to 1000 RPM and back and forth very quickly. I'm not sure what it is. What are codes 66 and 67? My repair manual does not mention these codes. Could the ECM be going bad in it? The gauges are acting wierd on it too. The oil pressure gauge will fly all over. It'll jump from 120 PSI, down to 60 and back again constantly, much too quickly to be an accurate reading. The temperature gauge also seems to be innacurate.

What year and trim level does he have?

92 SE

Code 43 is the knock sensor circuit. Could be a problem with the knock sensor, PCM, or PROM. Once again, you need a good diagnostic to determine which one of the three it is. Where did you guys match the code 43, the 93 service manual and the Chiltons both show knock sensor?

Here are a couple of helpers: The voltage between the knock sensor wire and ground should be 4-6 volts. The resistance between the disconnected knock sensor and engine block should be 3.3 to 4.5 kilo-ohms. Over 6 volts, means the wire is too close to secondary ignition wires. If it is not in-between the two resistances, it is likely a bad knock sensor.

I agree with you guys on the other ones. 34 is the MAF circuit. 66 means you have low freon. 67 means there is a problem with the cruise control switch on the turn signal, or possibly a problem with your brake switch for the cruise control. 67 needs a good diagnostic.