New guy, here. Thank you for taking the time to read this.

I recently got a 2001 Chevy Silverado 5.3 to use as a work truck. 198k miles, decent shape. For the past 5 years, it was only driven at low speed to the grocery store once a week or so. No codes being throw, but the service engine soon light is on. It has a few issues that I'm not exactly sure how to go about properly diagnosing. The gentleman that previously had the truck was an elderly diy kind of fella, so there are some wiring issues. I have read countless posts with similar issues, but just different enough that I felt like I should specify all of the problems I'm having (even though some are almost certainly unrelated to the big issue).

Oil and filter changed, new gas put in but didn't drain the tank, runs pretty well


The issues:

No license plate lights (easy fix, just listing everything I can think of)


Hood light burned the 5amp fuse out


Bit of a rough idle intermittently (not really bad, just a little rough. It smoothed out for a while then got rough again. Old gas burning through possibly? Injector cleaning coming soon


The ABS and brake light are permanently illuminated and the brake lights did not come on when I hit the brakes.

When the previous owner installed the trailer brake, he put the whole thing in with romex wire. Odd, but ok. It conducts and is (I suppose) good enough for now. However, the constant positive line was torn out of the brake switch. I opened up the connector, crimped it back and reinstalled the pin. Then I reconnected the line to 12v. Boom, trailer brake works and brake lights are working great.


The fuel pump sounds like it is constantly on and is loud

Now I'll be the first to admit I'm no master mechanic, but I've rebuilt quite a few engines in cars, trucks and motorcycles. NEVER have I heard such a noisy fuel pump that absolutely never shuts up. One caveat: the gas gauge fluctuates intermittently, so I think the sending unit needs replacing. I really doubt that can cause the pump noise, but it's worth mentioning. Another thread that had transmission issues (see problem below) said that his problem was a bad fuel pump? When he replaced it, the truck was back to normal. Seems odd, but I've seen weirder things I suppose.


The big issue-The shifting is slow and I have no overdrive

I can put it in first and take off, shift to 2, all good. 3rd only seems to grab at low rpms and when in drive it will get to around 4k rpms at 60mph or so. I think I felt 2 shifts, but it's really hard to tell. However, I can get to 20mph and put it in 3rd and it will drive. Just no OD. The trans fluid is red and does not smell burned. From what I've read of people with similar issues, changing fluid and filter did not fix it. I have ordered the input speed sensor (even if it doesn't help, it can't hurt). Soon I plan to drop the pan and check the solenoids. Could it be a clogged valve or bad solenoid? Fluid being ok seems to indicate it may be electrical rather than bad clutch packs, but I'm not entirely sure. Perhaps this is symptomatic of the noisy fuel pump like the other fella said??


Sorry for the biblical-length post, but I wanted to make sure you had full context. Could they have jacked up something in the electrical when installing the trailer light? Could it have been bad enough to cause the transmission issue?


The plan (probably not all necessary, but needs maintenance anyway):

Change spark plugs

Change tranny fluid and filter (not as a fix, but it needs to be done regardless)

Check 02 sensor

Check fuel pressure (if low, replace pressure regulator and FTP sensor)

Replace fuel pump

Check MAF sensor

Check knock sensor


So, what do you think? Am I missing something? Any input is greatly appreciated.