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Impala C0900 - fix info

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11K views 1 reply 2 participants last post by  J.D.  
#1 ·
Thread for info purposes

2008 Impala LS 3.5L

C0900 means the EBCM is detecting a higher than normal voltage.

I've searched the internet to solve this issue, C0900 code was the only code the car had. The check engine light was not on, the Service Traction Control System would display very intermittently and only for a brief second.

I couldn't find info on any of this and replaced both front ABS vehicle side wiring harnesses. Did not fix the issue.

Long story short, I checked ALOT of things and what I finally did was the following:
Hooked a multi meter to the battery and monitored voltage as I tried to get the car to flash the traction message. When it did flash the message (and make an annoying chime), the voltage spiked into 16v for a split second.

Keeping in mind I did not have any other errors, DTCs or messages regarding battery charge. I cleaned all of the grounds and battery cables prior to this.


At this point I replaced the alternator. And boom... no more issues. I double checked my battery voltage, tried to get it to "over charge" briefly turning on the headlights and rear defrost at the same time. And everything cleared up. So it seems the voltage regulator built into the alternator was having issues.

I hope this helps someone out there someday!
-I apologize for lack of pictures.
 
#2 · (Edited)
I'm in the same boat now the only difference is that my car is a 2010 CTS Caddy (and I haven't replaced my abs sensor wiring, lol). Mine just started doing this exact same thing right after replacing a failed alternator with a remanufactured one from Autozone. 1 single abs code c0900-07, service traction control, service stabilitrak pops up on DIC momentarily. I've now learned the hard way that it's best to use oem ac-delco alternators on these cars that utilize rvc systems (whether new or reman.) rather than going with the cheaper auto part store ones! So, I am curious, what brand of alternator did you put on your car that solved your issue? Did it ever happen again? I do have the lifetime warranty on the one I purchased from Autozone but I don't wanna waste my time swapping them out over & over again if I really just need 2 break-down and purchase a new oem alternator?