Oil Pressure Issue LM7
Thread Starter
Teching In
Joined: Feb 2025
Posts: 22
Likes: 4
From: Chicago
Oil Pressure Issue LM7 So this week my truck acted up a couple times
here is what happened.
2003 Silverado 1500
So first I went out to start my truck at 8 am, first 15 seconds sounded like lifter tick then went away. Hasn't done it since.
BUT I got a random idle Misfire where every like 10-15 seconds it will just quickly Misfire once. Raise the rpm by like 400, and drop right away within like 1 seconds.
Then out of nowhere my oil pressure dropped below 20 while driving and i got oil pressure light for literally 2 seconds and then it went back to 35ish psi pol pressure.
this all didnt happen on the same day. The tick was about 5 days ago. The Misfire i noticed 2 night ago. And yesterday while driving it did the oil pressure light bs.
compression is good. Oil was changed about 1000 miles ago with Mobil 5w-30 and nice K&N filter Do you guys have any idea what this could be an early sign of?
here is what happened.
2003 Silverado 1500
So first I went out to start my truck at 8 am, first 15 seconds sounded like lifter tick then went away. Hasn't done it since.
BUT I got a random idle Misfire where every like 10-15 seconds it will just quickly Misfire once. Raise the rpm by like 400, and drop right away within like 1 seconds.
Then out of nowhere my oil pressure dropped below 20 while driving and i got oil pressure light for literally 2 seconds and then it went back to 35ish psi pol pressure.
this all didnt happen on the same day. The tick was about 5 days ago. The Misfire i noticed 2 night ago. And yesterday while driving it did the oil pressure light bs.
compression is good. Oil was changed about 1000 miles ago with Mobil 5w-30 and nice K&N filter Do you guys have any idea what this could be an early sign of?
Last edited by GremlynnK; Feb 26, 2025 at 08:32 PM.
Thread Starter
Teching In
Joined: Feb 2025
Posts: 22
Likes: 4
From: Chicago
Should it have thrown a code if it had a hiccup or is malfunctioning? I did the scan, all I have is a p0300 Misfire but how would that affect my oil pressure. Like I Woukd understand if i had like misfire and a history code for Oil pressure or something.
I mean these ECUs overall ain't that smart. It doesn't even say which cylinder misfiring. Just p0300 Engine Misfire.
I mean these ECUs overall ain't that smart. It doesn't even say which cylinder misfiring. Just p0300 Engine Misfire.
TECH Senior Member
Joined: Jun 2016
Posts: 22,289
Likes: 3,615
From: Central Cal.
A P300 likely means an intermittent misfire among different cylinders, rather than just one.
A bad pressure switch doesn't throw a code. Replace it and put the engine on an analyzer to narrow the misfire down.
A bad pressure switch doesn't throw a code. Replace it and put the engine on an analyzer to narrow the misfire down.
Thread Starter
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Joined: Feb 2025
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From: Chicago
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So those trucks have a 3-wire short flat Pressure Sending unit, from stuff I've read part of that circuit goes through the PCM. If it gets low Oil pressure it kills the Engine as a fail safe to prevent it from locking up. Regardless of killing Spark or Fuel, there's the answer to your misfire possibly.
Could research it more and see if that's the case, symptoms here are telling me that little Sending Unit is going out.
Could research it more and see if that's the case, symptoms here are telling me that little Sending Unit is going out.
