Hi! This is my first time ever posting on a forum - please forgive any unknown etiquette on my part. I have a 2015 Chevy Malibu LTZ 130+k miles with an undiagnosed issue(s) that is stumping the mechanics I take it to. My car starts and initially runs fine with the check engine light OFF. As I am driving I will feel slight vibrations in the steering wheel and gas pedal. As I continue to drive the vibration will continue and then my engine light will start to flash (from being off) and I will get an alert on my dashboard to check Stabilitrack. I will then turn off my traction control (I was told to by husband who has no idea what is actually going on), which will make the Stabilitrack alert go away. The check engine light continues to flash for another 10 seconds or so then turns itself off. All while I am driving. Once I turn my car back on (whether 10 seconds, 10 minutes or 10 hours), the check engine light is back off but the issue will repeat itself, usually at least once a drive. I am at a complete loss, my mechanics are at a loss and I would appreciate any insight, advice or tips.
A flashing Check Engine light indicates a major engine misfire is occurring, and continuing driving the vehicle while this is happening can cause major damage to the vehicle. This includes to the engine and catalytic converter(s).
So, what needs to be determined is what is causing the major engine misfire.
Until then , do not drive the vehicle.
Tester
Flashing light= misfire.
Mechanic sees no stored codes? Odd
What were his words? Hmm, that’s odd?
He said he can’t fix what he can’t see?
The car has had very minimal use for the last 3 weeks, first waiting for an opening at the mechanic and then while they tried to diagnose - issue started a couple weeks before that. This usually happens once a drive, could occur multiple times a day (I drive 15 miles to and from work) but not multiple times a drive. The mechanic I used cleared some code related to the ABS but that obviously wasn’t the issue as it happened again the moment I picked my car up yesterday. They put it through the computer again this morning and he said no codes came up in the system. I have my car now scheduled at a chevy service station. I know ZERO when it comes to vehicles and maintenance but I know catalytic convertor issues are expensive, I sure hope it is not that!!
My gm has phantom issues.
Never a flashing cel. Never runs rough.
I get stabilitrak warning. Abs light. Traction control off,
Next day all lights are off.
Changed egr valve. Was told that might fix issue.
Had 1 code for wheel speed sensor. Changed wheel bearing. Same issue.
Wire harness to wheel bearing? Possibly.
One thing that can cause an intermittent misfire and yet not turn on the Check Engine light and set a code is a faulty crankshaft position sensor.
Tester
Thanks for the help! Hopefully the chevy service station will be able to figure out what is making this happen. It is frustrating that the problem is intermittent, I’d rather it just be broken!
Thanks for this info!! I will look into this and relay this to the chevy service as well.
The Stabilitrak message is secondary to the engine misfire that is triggering the flashing Check Engine light. From ChevyTrucks.org:
Anytime the engine isn’t providing a consistent engine speed, Stabilitrak and traction control automatically disable . Basically anytime you experience a misfire, rough idling, or some other performance related issue that causes RPMs to jump around, these systems will disable automatically
If you get the reason for the misfiring fixed, the Stabilitrak and traction control messages will stop appearing as well.
If the Chevrolet dealer can’t figure it out maybe you should take it to a good independent shop. If you don’t know of any ask everyone you know for a good auto repair shop. Eventually you will hear a couple of names repeated. Try one of them. Also, your car is common enough that any shop can handle it. You don’t need dealer service
I actually did this, I’ve been to 2 independent mechanics and neither were able to recreate the issue or diagnose - although, neither mentioned a misfire either though so I’m not sure I went to the best of places… the last mechanic referred me to the dealership and now I almost feel like going to the Chevy service is my last option but I will continue to ask around!
That first sentence really hit close - I can almost force the issue to happen by just trying to coast or reduce speed without the brake. When I actually hit the accelerator or brake everything feels nice and tight but when I am coasting is when I can feel the engine or something start to shudder (for lack of a better phrase) almost like when there is slack in a pulley and it kind of jolts until it tightens out again. That is the best I can describe of the vibrations I am feeling.
That sounds like a description of a misfiring engine to me. I expect the posters above are spot on,engine is misfiring for currently unexplained reason, and the the stabilitrak warnings are the result of the misfire problem; i.e. the first order of business is to solve misfiring problem.
The engine computer is constantly monitoring the engine’s rotation as you drive. “Misfire” means the engine computer doesn’t measure the normal momentary bump in rotation speed that it should when a cylinder fires. When a cylinder fires, a spark at the tip of the spark plug causes a charge of air and fuel to ignite. So a misfire problem is usually caused by either a faulty spark, or a faulty fuel supply. First job for your mechanic is to determine if the cause is spark or fuel. Until that’s determined, will be very hard to fix.
There are a few other causes of engine misfires, but those would be unusual for a 2015 unless it has overheated or been run low on oil.
Just FYI- clearing the codes is just like erasing the blackboard. The problem is never resolved by erasing codes. If the problem exists, the computer starts a counter. Each time the diagnostic program is run on the engine control computer, if the problem remains, it increments the counter. When the counter exceeds a preset value, the computer illuminates the check engine light, alerting you to the problem. For misfires, this is really bad for the engine and catalytic converter in your exhaust system. So when those are detected, the computer immediately starts flashing the check engine light to get your attention there is a bad problem.
Whenever the check engine light illuminates, diagnostic codes are stored in the computer memory. They are persistent unless purposely erased through equipment connected to the diagnostic port or by disconnecting the battery. If they can’t find any misfire codes (e.g. P030X where X is the cylinder misfiring) either they are not looking in the right area or there is another issue with the ECM itself which would be a very rare situation.
Your best bet is to have another diagnostic from a highly recommended mechanic or dealership service department. Be sure to tell them all the conditions you know that will reproduce the problem (e.g. coasting from 50mph, it always exhibits the problem) and let them do a proper diagnosis. Another example, if it needs to be cold to reliably repeat the problem, then tell them that and leave it overnight so they can test drive in the morning.
Good luck!
This is a great breakdown and explanation for me, thank you!!! I plan on giving all of this information and advice over to the mechanic so hopefully we have a starting point for this blind quest! I really appreciate everything! I plan on updating this once the problem is known and fixed in case this helps anyone experiencing the same.
Your explanation really helped me to understand what everyone is saying, thank you! I plan on giving all this information, what I see and feel (I even took a video to prove this is happening as noone else could get the issue to happen, but of course it is just of a light flashing, not much help!), and how to recreate the problem to the chevy service station. Thank you again!! I plan on updating this thread once the problem is known and fixed, in case anyone else is experiencing the same and could benefit!
You don’t need to explain to a mechanic what a misfire is, you do need to find one that will drive the vehicle for the distance necessary to replicate the problem. The information describing when the malfunction occurs is usually absent from the repair order and technicians normally don’t go for extended drives, especially if the customer is waiting for the vehicle.
This is exactly why I have composed a brief description of the problem and conditions I have noted that will make it happen and left that on the passenger seat or taped it to the dashboard for the mechanic that will be doing the work to see. More than once I have gotten the car back with a note thanking me for providing it. You can’t trust the service writer to capture the details accurately, if at all on the repair order.
This is a major failing of the service process at too many big repair shops where the customer interaction is removed from the people doing the work. The other is returning a NPF without at least consulting the owner for more details before giving up. I don’t fault mechanics, they are not incentivized to spend time solving problems, they are paid to do repair work on identified problems. Even then, the amount they get paid means they have to work fast and efficiently to make it worthwhile for them.
+1
My analogy is that simply erasing the codes is like touching-up X-rays in order to conceal a tumor or a broken bone.
I missed part where 2 shops could not find code. Did I hear that right?