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1998 Chevrolet Suburban P0300 and P0420: Engine Won't Start, Only Fuel Pressure & Codes

Model: 1998 suburban Fault Code: P0300 Posted: 2007-11-27 14:23

My 1998 4x4 Chevrolet Suburban gasoline-fueled engine suddenly stopped running. The only fault codes I'm getting are P0300 (random misfire) and P0420 (catalyst efficiency below threshold). The truck turns over but does not fire. I've already checked the fuel pump, which shows over 30 psi on the gauge (though the gauge maxes out at 30), and replaced the fuel filter as it was clogged. I'm wondering what other diagnostics to try before taking it to a shop. The vehicle is a 1998 Chevy Suburban with a fuel-injected engine, so any advice specific to this model would be greatly appreciated.

Related fault codes
P0300P0420
Comments (5)
Anonymous 2007-11-27 14:26

Have you checked for injector pulse or spark? These are key indicators of ignition system health.

Anonymous 2007-11-27 14:41

I'm not familiar with injector pulse, but since the truck has spark plugs, it's likely a spark-related issue. Could be a problem with the ignition system.

Anonymous 2007-11-27 14:44

Are you confirming that the ignition system is active? Do the spark plug wires show any visible spark when tested? If you can't verify injector pulse or spark, it might be best to take it to a professional rather than attempting repairs yourself.

Anonymous 2007-11-27 14:52

Yes, thank you! I checked what I could and agree with your assessment — it seems beyond my DIY skills. The codes didn't narrow things down enough, so I decided not to spend more time troubleshooting and just sent the truck to a shop. My truck is now being towed. P.S. I'm new here today and really appreciate the quick responses. I've bookmarked this site and will return when I have smaller issues that I'd like to fix myself. Also, I heard about a Master Code Book with more detailed diagnostics than standard code readers — do any of you know reliable sources or websites for such a book? Thanks again!

Anonymous 2007-11-27 14:59

Most regular users don’t need a master code book. The fault codes it provides are often not useful to DIYers. A basic OBD-II code reader is usually sufficient. Welcome to the forum!)