03 Chevy Silverado 1500 Z71 4.8l V8 156,000 miles. the check engine light blinks when hitting around 60 miles a hour on the freeway and will then stay on and blink every now and then with different intervals between blinking while also blinking for longer sometimes and shorter other times. I don’t have an OBDll scanner but I went to o Reilly and used theirs and the codes were: P0300 misfire, P0332 knock sensor 2 circuit low voltage bank 2. I replaced the spark plugs and wires with NGK ones that were bad so I took it to a mechanic and they put in new AC delco ones and the problem came back so I’m wondering what other things I could try to fix. I’ve been reading through some other forums on here and have seen suggestions for lifters, coils, 02 sensors, cleaning throttle body, worn pushrod and rocker, fuel injector, valve. Thank you!

 

when it blinks, it means "stop driving now, because you're doing expensive damage"

There are many things that can cause misfiring, so before replacing half the parts on your truck, you need to do some troubleshooting to narrow it down.
This means using a diagnostic tool to look at live data, like cylinder misfire counters, O2 and fuel trim data, intake airflow, etc, measuring fuel pressure, timing, compression, testing for spark, and so on.

 

Okay thanks Joe I’ll take it back to my mechanic and ask him to test for all those things you’ve mentioned. I appreciate the quick reply.

 

If your mechanic doesn't find any thing. He can try doing a Crankshaft variation learn procedure with the scan tool.

 

Okay thanks I’m here now so I’ll show him what you’ve said, he found that the intake manifold gasket was messed up and allowing more air than normal Into the engine and the knock sensors and their wires were messed up so he replaced both and the gasket and the light still comes back. Each time he’s fixed it he’s driven it for 40 minutes on the freeway and it doesn’t come on till the next time I drive it on the freeway?

 

run the scan again. You could have multiple issues going on.

 

It gave the knock sensor code and misfire code again, they said they’ll replace the sensor since it’s under warranty and they’d check where the wires run to see if there’s any damage and also said they found the fuel pressure is low it’s at 50 instead of 55-60 and drops to 49 when held steadily around 2,000 rpms which could be the issue.

 

yeah check the wires is what they should have done first. Not a great shop.

 

Okay yeah I left it so they’ll check out the fuel pump and the knock sensor wires hopefully they find the actual issue