Flashing check engine light - no codes
 

2 nights ago I was driving the SS when the check engine light started flashing. I stopped within a few seconds (was driving slow on dirt road), but the light was no longer lit. Put the code reader in - P0300 P0301 P0302. This is not the first time I've got these codes recently.

Yesterday, I swapped the 1 and 2 coil packs with the 3 and 4 coil packs, and cleared the codes to see what happens.

This morning on the way to work, the flashing CEL again for a couple seconds, then the light went out again. Checked for codes, but there were none, and no codes pending. I don't know what to make of this.

Let it roll! The computer will need a few run cycles to clear things up and determine if there are any problems .

Can't agree on that one. While it does take several drive cycles to clear standard CELs. Nothing good comes from it flashing. Albeit, I'm hoping it's a hiccup and goes away. At least you shut it down right away. How good is your reader? I have a cheapo and it will not see everything a good scanner has.

Flashing CEL, I'd say get it to a good scanner. Than see what comes up.

This is the reader I have. I'm using torque lite.

My understanding is: flashing means there is imminent danger of catastrophic failure of the engine. Steady is mostly protecting the cat.

P030x do not store necessarily. It will let one go, but set on the second (I think).

So then, Dan and Don you're suggesting to read the codes which aren't there and address the issues of these codes?
Similar to throwing parts at it?
I'm thinking if there is an issue the computer will tell you!
Now one thing that needs to be confirmed is are the grounds clean and tight!
The harness connections to the coils, injectors, all clean and tight?

No. But it's hard to believe a catastrophic failure is not setting a code. I would think the car would go into limp mode if the CEL was flashing. A simple occasional miss won't cause a flashing CEL.

Maybe you need a sophisticated code reader to look at the ABS and SRS/SIR systems.

It's a virus. That's doctor talk for "I don't know".

The car won't necessarily go into limp mode. It should, but I've had a flashing CEL before. It means stop immediately and figure it out. I know you're aware of this RJ, since you did shut it down.

It is concerning that no codes are stored. If it was indeed a failure it would most definitely store that code. I'm going to stick with Don on this one, it needs a doctor's visit!

How's your battery? And as blue suggested, check out those grounds. Charge level and grounds do play havoc on our systems but I wouldn't think you'd get a flashing CEL. Possibly if all the dash was flashing. Which it isn't.

Keep us posted buddy!

From the google results, flashing CEL is usually misfiring, flashing to protect the cat. So it looks like Don has the right idea, just backwards. I also think Don's onto something, it may not be engine related. After all, If it was engine related, why wouldn't it throw a code, I'd take even a pending code! And why would it flash for only 2 or 3 seconds and go out? Most driver's would likely not even see that in time to know what the heck it was.

Maybe it wasn't "flashing", but instead was thinking about lighting up 2 or 3 times in rapid succession. Still doesn't explain why there was not even a pending code. Or does it?

I actually haven't stopped driving it, drove to work and back today(~70 miles round trip) no light, no flashing, and still no codes. So with the trip home from work yesterday, that's just over 100 miles with no apparent issue.

I'll try to get to a tech2 after work tomorrow, But I'm kinda thinking like Oldblue, that if it were a serious engine problem, there would be codes, or at least flash that dang light long enough to really notice it!

I'm not poo-pooing or ignoring anyone's advice, I did post asking for help. But if I leave it at home, I won't get home from work in time to get it to a Tech2. There's a dealer in the town between home and work that I should be able to get to before they close.

Thanks, everyone, I'll post results back.

I'm kind of thinking ABS those codes do not show up in a normal scan, you need a ABS capable scanner. Normally the trans will set something.

Anyway, it is odd.

Yes, odd indeed.

Turns out my mechanic has a nice snap-on scanner that can check every system, and he was open late enough so he could scan today. But still nothing, no ABS, no airbags, nothing but old history(before this latest flashing the other day).

So I'll just have to keep monitoring it. I still don't even know what caused the misfires, But I'll take it one day at a time. Maybe it was misfires, but not enough to trigger a code?

? Keep us posted!!

Roger, Roger!!


https://40.media.tumblr.com/ea6bad99...4k5o1_1280.jpg

But my name is Steve! Just don't call me Shirley.

2 misfires in a drive cycle will set a CEL the first sets pending. If it happens in 2 consecutive cycles it goes "permament"/"historic". That's what puzzles me. Misfires are a "imminent cat killer" so they only get one chance.

To kill a cat??? Or slang term for catalytic converter???

only if they are playing a piano.

There are a number of codes that can be set that will not force a "limp-in" mode situation, but none would normally be associated with failures bad enough to cause a flashing SES light.

The other odd thing is that any issue bad enough to make the light flash is inherently bad enough to set a "hard" code, meaning that even if the situation causing the light to flash resolves itself, the light should remain illuminated and just go solid after the event.

This, along with the fact the car did not go into "limp-in" mode leaves me inclined to agree with RJ_RS_SS_350 that it may have been a series of soft codes identifying an intermittent problem rather than the "stop now" flashing of a qualifying event.

The only other option I can think of is that you're experiencing an ECM/Electrical problem, That's about the only way I can think of it occuring a second time and not have a single "pending" code.

The fist time it did set the 300 301 302 codes, but, yeah the second time, nothing. He said the reader communicated with every module on the vehicle and showed no issue at all.

Bonus!! Drive her McIver!! But keep an eye on the CEL!!

Got the flashing CEL again last night, this time it gave me pending codes. It's the same P0300 301 302. So swapping the coil packs did not change the codes. I'll try some new spark plugs and see what happens.

AC Delco Iridium , spark plugs!

Also make sure to check the gap, while it's been said they are pregapped I've found that the gap was more. If you still have a problem try closing up the gap, try .025-.026 and see if that helps.

If you touch the whisker it will break!

Forgot to mention that.... yes it will, you have to be very gentile.

Thanks donbrew.

Well, I'm not Jewish, so I am gentile. :wink:

I'm not Jewish, but I am ..ah.. well, you know, I was born in the 50's in a military hospital, it was automatic. So I'm almost a member of the tribe, but still gentile.

Gotta love spell check some times:lol:

Oye voy!

After reconfiguring my PVC system to phase 3 of testing, I was on my way to the hardware store when I realized I had forgotten to hook up the MAF sensor wiring. Pulled over and reconnected it, had driven about half a block.

1 or 2 more key cycles (only a mile or 2) I got a solid CEL, P0301 misfire. So I don't know if it's from driving with the MAF disconnected or if it is injectors. I put the new plugs in 300 miles ago.

It's been 150 miles with no codes or CELs. Just had a smog check.

I've been having an issue with my catch can setup, causing excessive crankcase pressure. Small amount of oil was blowing out the oil filler cap. I wondered if there might be a correlation, so I read this thread again, checking the dates of my first flashing CEL/misfire codes. My problems in this thread started while I was still in phase 1 of testing, before I had the issue with the crankcase pressure. And I passed the smog check before I corrected the pressure problem. So no correlation.

Well, the P0300 P0301 P0302 issue has started again. Once or twice a month over the past 2 months. Driving just over 70 miles a day. Since moving the coil packs and changing the spark plugs didn't seem to change the codes, I don't think those are the source of the codes.

While making a new thread about catch cans, I came across a post I had made in February, 2016. In it, I mention I've only had the fuel pressure code the one time(I think, memory ain't the best, certainly haven't had it since then). I cannot recall what the specific code was.

Also, when I change the oil, the oil level is good. When I check the oil level at a later date, say, months later, the oil level is high. I've seen threads that say this is normal. But it could also be the HPFP leaking fuel into the crankcase.

Does the oil smell like fuel?
Have you run Seafoam thru the oil ?
Could the misfire codes be loose connections?
Sometimes the simple things get overlooked while our imagination looks for a bigger picture problem, think about how many think it’s the ECM or BCM when it’s usally a loose fuse or relay or ground wire.
When was the last time you cleaned the throttle body? Or ZmAF ?
These can all cause a misfire.

Does the oil smell like fuel? Maybe, hard to say. It's stronger than the new oil I have. It's been a long time since I've huffed gasoline vapors :nuts:
Have you run Seafoam thru the oil ? No, never.
Could the misfire codes be loose connections? If you mean at the coil packs, they are snapped in tight. Moving the coil packs to different cylinders didn't change the code.
Sometimes the simple things get overlooked while our imagination looks for a bigger picture problem, think about how many think it’s the ECM or BCM when it’s usally a loose fuse or relay or ground wire.
When was the last time you cleaned the throttle body? Or ZmAF ? When the valves were coked, and I removed the manifold. But it really wasn't dirty even then. Have never cleaned the MAF. It looked clean last time I looked.
These can all cause a misfire.

I'm certainly not ready to buy a new HPFP, this happens so infrequently, it's going to be hard to nail down. I just had forgotten about the fuel pressure code, thought it might be relevant.

But really, it seems to be NOT plugs or coils. If it were a bad electrical connection, I would expect to see it more frequently. So at this point, I'm leaning towards a fuel issue.

Ugh, I hope it's not injectors or fuel rail, I'd have to remove the intake manifold again! Well, that would allow me to make a progress report on the intake valves.

Hmmm, another commonality is this: The last few times it has set the CEL have been at the same location, slight downslope, coasting in gear, right before the parking lot at work.

Hold the dripping dipstick in a flame, if it ignites it's gas.

Higher oil level is only "normal" when hot or parked on an incline.

I am betting on the HPFP, It is pretty sophisticated the way it regulates pressure. I think it is not reacting fast enough when you let off the pedal. So it is dumping fuel into the cylinders

We don't need another "blame the BCM" thread!

"The last few times it has set the CEL have been at the same location, slight downslope, coasting in gear, right before the parking lot at work"

That would be on trailing throttle - perhaps indicating it is running too lean?

I was thinking if it was running rich, the plugs should show that on a reading of them.

My understanding is that, when coasting in gear downhill, the fuel is supposed to pretty much shut off. Is this true?

It doesn't light up the CEL when doing the same down a longer, steeper downslope (1 mile, 7% grade)

It's so infrequent, not sure if evidence would show up on the spark plugs.

At least it's not flashing anymore.

So, you didn’t read my suggestions
Check for .....

Yes, I did.

The oil on the dipstick doesn't burn, so I guess there is no fuel in the oil, so the HPFP is less suspect.

No Seafoam in the oil.

The connectors that snap into the coil packs are snapped in nicely. What other connections should I check? I'm gonna have to see if I can remember if I've messed with any connectors since just before this started.

Haven't messed with fuses, relays, or ground wires. The climate here is such that no corrosion forms on these.

I could try cleaning the MAF. I think if it were that, though, it wouldn't be just these same 2 cylinders every time. The throttle body is a real pain to get to, to clean it, or even just to inspect.

OK, looking back, this started shortly after removing the intake manifold, shell blasting, catch cans. So, I had several things disconnected. The throttle body had just been cleaned.

I guess I'll get some MAF cleaner, and some Seafoam for the gas tank(maybe the injectors are dirty, although I try to always use Top Tier Premium, usually Costco).