1999 Chevy Silverado Code 0402, P0402

JERGEN

MEMBER
1999 CHEVROLET SILVERADO
V8
2WD
AUTOMATIC
18,400 MILES

My 1999 Silverado is showing codes 0402 and P0402. My Manual says it's the catalyst not performing at optimum efficience left bank. I can't find anything else about this code in the manual. I don't want to start changing parts without a solid doagnosis. What do you think? The truck is running fine, maybe a little high gas mileage, but I don't know if that's because of what's tripping the code or the high mileage.
What do you think?

2 Replies

BRIAN 1

MECHANIC
1,030 POSTS

Do you mean p0420, p0402 is an egr code for a 6.5 diesel. It probably needs a cat converter, the diagnostic says to check for exhaust leaks, dents in the cat or the exhaust. If no dents and the dtc is cleared and resets replace the cat. Looking at the milage on this vehicle, over time cat converters break down internally over time and are not efficient thats why this code came up. If you replace the cat if you can go with an OEM converter because the aftermarket ones normally dont work to well and are nothing more than a hollow pipe and when installed they seem to reset the p0420 code. Post back with any other questions.