Anyone on here a GM service tech, or PCM guru?

[Samckitt]

The SES light on my 03 silverado flashes every once in a while. Never stays on, just blinks 8 or 10 times then OK for a while. The manual says something about if this happens when pulling a trailer to slow down. I am not pulling a trailer, & if I slow down it will continue.

Any thoughts?

Thanks

[LateNight72]

The SES light will also flash if the PCM thinks there is an immanent possibility of the catalytic converter getting damaged.

So a possible misfire?

[Samckitt]

I don't feel any misfire. On any other vehicles I have (no LS motors), I can feel it.

Maybe I will change plugs & see if it fixes it, wires too.

[Vegas69]

An emission fault like a misfire will keep the light on steady through that drive cycle. If it isn't present at next start up it will clear. You need to get it on a scan tool. There should still be a record of the fault even if it's intermittent.

[Samckitt]

I thought my wife said something about pulling a trailer in the manual. I was driving while she read it. But I just went out & got it & it says:

If the light is flashing.
The following may prevent more serious damage to your vehicle:
Reduce vehicle speed.
Avoid hard accelerations.
Avoiding steep uphill grades.
If you are towing a trailer, reduce the amount of cargo being hauled as soon as possible. (That is the only part I remembered)

If the light stops flashing and remains on steady, see "If the light is on steady".

If the light continues to flash, when it is safe to do so, stop the vehicle, turn key off wait at least 10 seconds and restart the engine. If the light remains on steady, see "If the light is on steady". If the light is still flashing, follow the previous steps, and drive the vehicle to your dealer or qualified service center for service.


Also on the same page:

Light flashing - A misfire condition has been detected. A misfire increases vehicle emissions and may damage the emissions control system on your vehicle. Dealer or qualified service center diagnosis and service may be required.
Just as Todd said.


So I will try the plugs & wires & see if it continues. It is not all the time & not on all trips.

[6'9"Witha69]

When was the last time you cleaned the TB?

[Samckitt]

Cleaned the throttle body....... Uh....... :-)

[LS1NOVA]

Have someone scan it for codes, some auto parts stores do it for free and go from there. Rarely see a plug wire bad. A little fuel injection cleaner wouldnt hurt though.

[6'9"Witha69]

Yeah, get some TB cleaner from the local auto place (like an STP) and clean it out.

[Samckitt]

Well yesterday I cleaned the throttle body, replaced the air filter, olugs & plug wires. And the flashing check engine light continues. Seems to be occurring more often when going downhill, when there is a slightly less load on the engine.

I guess I am going to have to take it to the dealer & spend the rediculous fee for diagnosing it.

[MonzaRacer]

Have someone scan it for codes, some auto parts stores do it for free and go from there. Rarely see a plug wire bad. A little fuel injection cleaner wouldnt hurt though.

OK So who taught you diagnostics?
Plugs wires never go bad? HUH! So for the last few years of replacing plug wires that will glow while engines run or the cars show so many misfires it maxes out the counters, I must have been doing wrong.
Now as for the issue, when a ses light flashes the offending problem is ACTIVE, like a misfire, injector fault, torque converter slipping, etc.
Regardless of the make, get it to a true diagnostic tech, and let them drive it under similar conditions, get it to do it for them.
Now if it has set codes great, it should also also have freeze frames saved pointing to the issues.
Another thing is dont forget the original parts are pretty darned good on nearly stock vehicles.
Had a Camaro come in the other day with a "tune up" from one of the stores in our chain, big problem the standard tuneup is Champion plugs, and the LT didnt like them one bit. It also still had bad cap/rotor/dist/waterpump and other mechanic should have never touched it.
Repaired the water leak and installed good parts(well its got a set of MSD wires)most of them OEM and tada the miss that was mild before but now would barely let it run because the mechanic "threw" a "tune up" at it.
Sam give me a shout if you continue to have issues.
Lee Abel
AFTERMARKET PERFORMANCE

[Samckitt]

On Monday it was doing it like crazy for a while. There was a couple of miles that I drove that it blinked constantly. I was beginning to think I made it worse instead of better. As it was blinking & I was cruising at around 60, I put it in neutral, shut it off for about 10 seconds & started it back up. From then on it was fine, & I don't think I have seen it do it since. Next time it does I will go straight to someplace like Autozone & have them check it & see what they get. Thanks

[MonzaRacer]

Sam Ill give you my cell, if you ever want it scanned with real scanner and someone who knows whats going on I work for Bloomington Pep Boys and have a new Snap On Solus Pro sooooo.
Check your pmS.

[Samckitt]

OK so today I was out & about when the SES light started blinking again on the truck, & I was close to Autozone, so I stopped in & had them get the codes.

Here they are:

P0300:
Cylinder misfire detected - random cylinders.
Explanation
The PCM monitors the crankshaft speed and has detected a misfire condition.
Probable cause:
Ignition system fault - spark plugs, ignition wires, coil
Vacuum leak
Injector fault
High or low fuel pressure


AND, (this one is odd)
P0650
Malfunction indicator lamp control circuit fault.
Explanation
PCM has detected an improper voltage level on the MIL circuit with the light commanded on.
Probable Cause
Open or short circuit condition
Failed driver circuit in the ECM


Remember I have changed the plugs, wires, Air filter. Have a fuel filter, just haven't changed it yet.

[LateNight72]

Could it be a short in the wiring harness? Especially since you are getting that P0650 ?

[paul67]

check the o2 sensors they could be carboned up ,how many miles has it done ,also have you changed gas stations,or fuel grade.

[TBART70]

Very common to have an intake vacuum leak (usually on cold start/ then a random miss fire till it warms up). It can get bad enough to do it all the time. Spray carb cleaner at the intake and watch to see if the front O2 sensors stick rich ( obviously needing a scan tool ). If you can get a scan tool, look at the long and short term fuel trims in freeze frame data. If they are high at the time of the miss it is possible that there is a vacuum leak.

[Samckitt]

check the o2 sensors they could be carboned up ,how many miles has it done ,also have you changed gas stations,or fuel grade.

It has about 120k on it, I don't stick to one gas station, I buy it wherever, always usually use the same grade.

[TBART70]

did you fix it?

[Samckitt]

I haven't done anything more to it other than put some fuel injector cleaner through it & haven't seen the flashing SES light. So is it "fixed"? Not 100% sure yet.