: Random Stalling with ZERO CODES...???? Please Help!

07-09-11, 05:43 PM
I've been researching the feeds and have found some answers, but thus far nothing has worked...
I have an '05 STS with 79000 miles. Just last weekend, the car started stalling without warning, no shaking, just dies. It's happened intermittently, in any circumstance (idle, accelerating, at a stop, incline, any gas tank level, at any speed, etc...). My sister's BF is a car genius, and plugged in his scanner, and zero codes resulted... No Check Engine Light, nothing. It could stall once while driving or 9+ times and sometimes not at all, and I haven't been driving long distances (more than 10 miles) lately... I'm not excited about taking it to a dealer (not under warranty anymore), as they'd likely charge me out the whazoo for a diagnostics fee and leave me with no solution... We've checked the battery (6mos old), its connections, fuses, what we could under the hood, etc... It still stalls. The only light I've seen on the CID is "Service Vehicle Soon" and that was once last weekend, when this stalling started to occur... The push-start button has two orange lights, one on the bottom right that lights when the ACCESSORY is only on, and the other on the bottom left when the ENGINE is on. Since this stalling started to occur, the left light is not lit when the ENGINE runs... I'm wondering if this has anything to do with the stalling, or if the bulb is merely out...
Does anyone have any advice?!? PLEASE! Other than the random stalling, the car runs fine and smoothly... Just randomly dies and immediately starts right up again...

07-09-11, 08:23 PM
Hmmm. I find it difficult to believe there were no codes when you had a recent service vehicle soon light. There will likely be something stored as a history code, even if there is nothing current. What type of scanner was it? It may not be telling you the whole story, especially if it wasn't designed for CAN bus vehicles.

Does it just outright stall, or does it chug first. Could be an occluded fuel filter or a fuel pump that's intermittent. Like I mentioned, make sure the scan tool is working correctly first.

07-10-11, 04:19 PM
Thanks for your help!
It doesn't chug first... It's just like a microsecond of a bad connection or loss of power...it just dies... Although the radio still stays on and lights too, so it's not a total loss of power... It just stalls without warning, then starts right up again, and then runs smoothly, until it stalls again... ??? I did read about the compatibility issues with scanners (OBD vs. Scan-Bus), and my sister's BF, who's the car genius/certified mechanic (although he mostly works on BMW maintenance nightmares), his scanner is an OBD... Although he says it should read something from being plugged into my cadillac... I've thought about trying to make it to Autozone, to use their scanner, but he says they would have the same type of scanners... He's looked under the hood, checked a bunch of connections, cleaned some corroded knobs, checked the battery connections, etc...Either way, I'm trying to avoid going to the dealer and having to blow a bunch of $$$ for them to not find a solution... I've been constantly searching these forums to see if any of the possible solutions will work...
Thanks, Ddalder!

07-10-11, 06:47 PM
No disrespect meant to your sister's 'genius' BF but find a real mechanic that understands Cadillacs. I understand your desire to avoid dealers but most do know more about our cars than the uninitiated. Many independant shops have the equipment needed to service these cars but many don't.

Once you get the codes associated with your trouble this forum is a great resource. Make sure to note any aftermarket changes to your STS because many have common side-effects.

07-10-11, 07:24 PM
Thanks, Echas3

No disrespect to dealers... I'm just going by experience... All good advice, and I haven't done any after market changes, other than new tires, brakes, and battery...


07-10-11, 08:23 PM
What I can tell you is that even the GM Tech2 Scan Tool requires an add-on module to communicate with GM vehicles that use the CAN bus architecture. For this reason I mention confirmation of the tool being used. The thought that the other scan tool should retrieve at least something from the car I believe to be inaccurate. My GM scan tool won't either (without the CANdi module) simply because of the bus architecture and communication protocols are vastly different.

More of an FYI than anything, some vehicles do have a combination of legacy type 'Class 2 Serial' modules and CAN bus modules. Inter-communication is achieved by way of a 'Gateway' module which will be one of the many modules installed in the car. The designated 'Gateway' module (which can vary between different GM models) will facilitate communication between older class 2 serial modules and new CAN bus modules by handling data conversion and relaying.

Hopefully you can get this all sorted out :)

07-11-11, 02:06 PM
Thanks for all the advice!
So, because I haven't received any codes on the OBD scanner, I decided to go to Autozone and use their Scan-Bus Scanner/compatible with GM/Cadillac, and again, No Codes... I know it's not a Cadillac dealer, as I'm trying to get an idea of what the problem is before going there... The guy at Autozone said there aren't any codes because my "Check Engine Light" is not on... It hasn't been on, other than my gauge reading "Service Vehicle Soon" when the random stalling occurred over a week ago... So, I'm not sure what is wrong now... I'm grateful the car hasn't stalled in almost two days, so we'll see. I'd like to be able to drive though without feeling like it could stall at any moment and not have to drive in the slow lane constantly paranoid...
Any advice...?
Thanks, All!

07-11-11, 08:19 PM
As stated above, not many code scanners will check the history. DD knows his stuff.

Take it to someone that knows Cadillacs and has the right tools.

07-12-11, 09:40 AM

I had a 96 Jimmy that would do the same. Drive down the road, all of a sudden, engine dies and your coasting, then it starts right back up. It happened a few times and no codes. I replaced the Crank Position Sensor and problem was resolved.
It was as if there was no signal from the CKP, therefore engine= off, and no code. I know it's not a Caddy (which I believe have two CKP), but maybe some food for thought?

07-12-11, 12:05 PM
Also, If your IAC valve is gooked up it will not show a code.

07-12-11, 12:23 PM
Just to throw in my 2 cents, there are many systems of codes on the Cadillacs that will not set the Check Engine Light. That light is only for PCM codes. The Service Vehicle Soon message would indicate a problem from another system, possibly an electrical fault (it could very well be a problem with the start switch or something else). The car will diagnose so much on its own, you really do just need the right tool to read the data. The old models had a built-in diagnostic system, it's unfortunate that GM discontinued that.

I wouldn't discount anything as a possibility, but the PCM has self-checks for the IAC and will set the CEL if it detects the idle out of range or not being controlled by the signals.

07-12-11, 10:11 PM
With all due respect to the folks at Autozone, it sounds to me like the staff member doesn't have a complete understanding of the vehicle systems.

Some GM vehicles have two lamps. One is an engine light (GM calls this an MIL or Malfunction Indicator Lamp) and if present, the other is a "Service Vehicle Soon" lamp. Most often the MIL relates to emission faults. Systems that illuminate this can vary from model to model and be depnedent on whether the vehicle also has a "Service Vehicle Soon" lamp. The only real way to get to the bottom of things is to know for certain what code(s) have caused the indicator to illuminate.

When a vehicle is scanned, a GM Tech2 will actually specifiy which of the codes (if there are several) that requested (or turned on) the MIL. What the folks at Autozone haven't told you is that (as mentioned), there are many faults that won't actually turn on the lamp and the codes are only discovered when the vehicle is scanned following a customer complaint for a specific problem.

Generally, only current codes will cause the MIL to illuminate. Once the vehicle no longer perceives a problem, the code will become a history code and the indicator typically won't appear. Some scanners won't/can't check for history codes. I've scanned many vehicles to find a boat load of codes but no MIL or Service Vehicle Soon lamp. Over time (usually based on a preset number of ignition cycles where no fault is detected), even history codes will clear on their own. Of course the longer you wait, the more likely it will be a history only code won't be there once it is finally scanned.

Bottom line here... there are a number of things that can cause the symptom you describe. The only way to be absolutely certain whether there are codes or not is to make sure the car is scanned with a tool known to read all GM codes including any stored in history. I'm not saying you do have codes but I wouldn't trust a non-specific tool without more information about its capabilities.

The other point to consider is that only some DTC's (Diagnostic Trouble Codes) are required to be the same between all vehicle manufacturers to meet applicable legislated standards. There are many codes that can set which are manufacturer specific. There are also sypmtom codes (as GM calls them) which allow an additional two character code to be associated with the DTC. This provides additional data about the fault without the need to assign another DTC.

For example:

DTC B101E - ECU Software Performance
- Symptom 4A - Checksum Error
- Symptom 4B - Calibration Not Learned

Previously, this would have required two separate DTC's. Now, it's one code with two different "sub" (or symptom) codes.

So as vehicles become more complex, a single DTC number may only offer a part of the puzzle. Scan tools need to be more complex to function correctly and, as mentioned, manufacturers have the ability to implement more "unique" codes not applicable to other makers. I question auto part retailers keeping their technology "current". There is a large cost with this and I'm not convinced it's economical given the variety of manufacturers and models and their target market.

07-14-11, 02:08 PM
Thanks ALL for your advice/input!
I'm grateful, because my cadillac hasn't stalled in 5 days...! Don't get me wrong, I'm still driving in the slow lane, just in case it stalls... I'm consciously paranoid that it is going to at any moment... I am grateful for all the input, and if it stalls again, I'm going to a cadillac dealer to diagnose and fix the problem, which I'm hoping they'll be able to do...

09-14-15, 02:30 PM
My 05 STS just started stalling yesterday. Runs great, then shuts off without warning. twice yesterday and six times today. We have a Snap on Versus and Solus Edge scanner and neither scanner pick up any codes or irregularities. Did you find anything conclusive with your experience? I appreciate any help you can give me


09-14-15, 05:56 PM
V6 or V8?

12-05-15, 05:05 PM
I just bought a '05 STS with the N* V8. I'm experiencing the same issue. Any help and definitive is greatly appreciated.

12-05-15, 11:53 PM
Loose intake manifold bolts? Don't over-tighten, I think it's only 11 inch-lbs.