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Old 10-07-2019, 08:50 PM   #3
Vuegreenline
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Join Date: Oct 2019
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Default Re: 2007 Saturn Vue Green Line (Hybrid) 12V battery not charging redux. Also, cut wi

Thank you, Bern. I spoke with the seller today, and he finally told me that he bought it that way, and it ran fine. The problems started when he changed the battery. I did some work on it today to try to find out if the alternator-generator is actually working, as I don't like to replace parts that work. Since the cables from the alternator-generator are not exposed, I didn't know how to test the output, so I took everything apart so I could put my voltmeter on it.
See pics. I turned the engine over and measured the voltage on the three black, white and red cables. The voltage on my crappy-but-functional Harbor Freight meter varied from about 19 to 22VDC. The voltage on either side of the MEGA black fuse was 14.1V. The voltage on the blue cable going back to the hybrid battery (which was replaced under recall in 2010) was 41V. The 12V battery was of course 14.1V. Then, after a while, I heard a change. The engine sounded different, more muted somehow. The voltage on the alternator-generator cables dropped to 2.3 to 3 volts. The MEGA and 12V battery voltage dropped to 12.2V, and the blue cable to the hybrid battery varied between 12 to 22V. Obviously, the 12V battery was no longer charging; I was running the engine on the 12V battery, and voltage was dropping fast. What I still don't know is if the problem is the alternator-generator, the BECM, or something else. I suspect it's the BECM, since it's the most expensive part, and I can't find any used ones. However, this article:
underhoodservice.com/power-assist-servicing-saturn-vue-hybrids
points out that malfunctioning temperature sensors in the hybrid battery can cause the BECM to 'shut down the system,' meaning the charging voltage from the alternator-generator. Oh, yeah, here are the codes I'm getting:
U0111, P0AFB, and U1897. U0111 is 'lost communication with battery energy control module A,' and P0AFB is 'Hybrid/EV battery system voltage high.' After a brief search, U1897 is also 'lost communication with battery energy control module.' Tomorrow morning I plan to turn over the engine and see if the battery charges for a while before failing. Is there any way I can be sure it's the BECM, or the temperature sensors in the battery pack, or something else?
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