Jim Grant's Tech Tips
‘98 GMC Jimmy, Trouble Code
Q: Can you tell me what code #P0301 means? The vehicle is a ‘98 GMC Jimmy V-6 4WD. The service engine soon light was on but has since turned off.
Diagnostic Trouble Code (DTC) # P0301 is the computer reporting a misfire occurring in cylinder # 1. This means that for some reason #1 cylinder did not correctly burn the air & fuel mixture in that cylinder. The cause could have just been a bad start to the day, worn ignition, engine components, vacuum leak or fuel system problem. There has been a problem with the fuel injection system in certain GM type trucks and SUV’s from ’96 up to ’02 and some ’03 year vehicles equipped with 4.3, 5.0 & 5.7 liter engines. When the problem first starts occurring it is often on start-up. The engine will idle and run rough but often times the condition clears up after a short distance of driving. This condition can turn on the check engine light and in some cases even case it to flash. However, once the problem leaves the engine runs fine and the check light will often go out with in a day after. The computer will store an engine misfire related code. This problem can be intermittent at first and build with frequency. The problem is the result of carbon buildup in the fuel injection system and engine. This has become enough of a problem that GM is extending or should be said issued a special policy for California emission equipped vehicles which extends the coverage to 10 years or 200k miles whichever is greater. Just a note to the readers, California emission equipped vehicles are sold in many areas of the US. In the event your vehicle is not covered by the “special policy” you should ask your local repair facility or GM dealer about carbon treatments for the fuel system. Regular treatment of the fuel injection system with a quality additive can minimize or even prevent system problems if treatment begins early.