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My 03 Sierra with 5.3 has a check engine lite. Scanning it revealed a code P0307 cylinder 7 misfire. I changed the coil and the code changed to a P0300 multi cylinder misfire. After a few resets it reverted back to P0307. New plugs and wires did not help. (at 96K mile they were about due anyhow) Swapping coils between 1& 7 caused the code to temporarily go to P0300 then back to P0307.
Other symptoms are rough idle, stumble on acceleration. Decrease in gas mileage.
Scan tool also says:
"CAT not ready"
"EVAP not ready"
Don't know if they mean anything or not.
You guys have any experience with this stuff?
Other symptoms are rough idle, stumble on acceleration. Decrease in gas mileage.
Scan tool also says:
"CAT not ready"
"EVAP not ready"
Don't know if they mean anything or not.
You guys have any experience with this stuff?