Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum banner
1 - 14 of 14 Posts

·
Registered
2005 chevy trailblazer_ls
Joined
·
7 Posts
Discussion Starter · #1 ·
hello
im looking for some help. I have an 05 TB with I6. My battery light comes on randomly. I have load tested the battery (OK) and replaced the alternator. And it still comes on, i cant pin point a specific thing that i or the TB does to cause this. But ill see the volt guage drop down to around 9 volts the lights will dim and the battery light comes on. This only happens when i am off of the gas or idling in traffic. but when i get back on the gas the guage goes back up to around 13v and stays there for a wile and then it happens again. the TB does not stall, the eng does idle down like it is going to stall but doesnt. alternator connections are good and tight , battery cables are tight and clean. i cant figure this out. any help would be great.

thanks
joe
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
Do you have a meter? What's the voltage ON the battery when this happens?

The gauge is driven by the PCM, so somehow the PCM is seeing low voltage. That could be a bad ground, OR an oxidized fuse power connection to the PCM. I would start by unplugging and replugging all PCM-related fuses in the front fuse block.

You checked battery and alternator cables - what about the grounds where they connect to the fender?

Was the alternator replaced in response to this problem? Who diagnosed that?

It could also be the start of the dreaded ignition switch failure, which is a cheap and easy DIY fix. Run a search.
 

·
Registered
2005 chevy trailblazer_ls
Joined
·
7 Posts
Discussion Starter · #3 ·
i havent checked the voltage i will, the ground cables are good also, i took the advise of a person that i thought knew what he was doing and changing the alternator well there was $120.00 dollars down the drain but i know it is not the alternator now. ill chech the pcm fuses.
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
How often does it do it? Can you catch it in the act and check a PCM fuse with the meter to see what the voltage is on the fuse? (Many fuses have poke holes to check the voltage on them when they're running) And finally - what's the voltage gauge read when you're idling at 600 RPM with the head lights on and again when they're off?
 

·
Registered
2009 chevy
Joined
·
6,431 Posts
Hey Bill, we might have a contest here.

jbranner, I'm reading that this problem only happens when idling and at this time, the rpms are dropping off.

I'll suggest, a dirty throttle body.

And, if it's not the problem, a clean one is not going to hurt.

We have a very detailed step-by-step in the Articles section, take a look-see.
 

·
Banned
2004 gmc
Joined
·
26,181 Posts
That's where my question was heading with the "head lights on and again when they're off", BUT I admit to not thinking it's the primary reason since there was no report of the engine stopping.

Joe - just so you don't think we're nuts - Ray and I (and some others) do this from time to time - we try to be the first to accurately call a new member's problem and try to save them a bunch of money with an accurate fix first time.

Not like your "friend" did by recommending the alternator. :no:

Anyway - cleaning the throttle body is NEVER a bad idea on our trucks. Some folks need to do it every 30K miles.

http://forums.trailvoy.com/articles.php?do=viewarticle&artid=91

I try to think of us as Trailvoy's diagnostic team:

 

·
Registered
2005 chevy trailblazer_ls
Joined
·
7 Posts
Discussion Starter · #12 ·
sometimes the guage on the dash will read 13-14 volts and sometimes around 9 volts when at idle, but not all the time. it does it more when the engine is hot than when cold.
 

·
Registered
2003 gmc envoy_slt_xl
Joined
·
270 Posts
sometimes the guage on the dash will read 13-14 volts and sometimes around 9 volts when at idle, but not all the time. it does it more when the engine is hot than when cold.
Just go and clean your Throttle valve body. Poor idling causes the battery light to blink as there's not enough rotation to fully charge the battery.
Any electrical fault will triger the SES light. Do you have any?
 

·
Registered
2006 chevy trailblazer_lt_ext
Joined
·
254 Posts
Hey Bill, we might have a contest here.

jbranner, I'm reading that this problem only happens when idling and at this time, the rpms are dropping off.

I'll suggest, a dirty throttle body.

And, if it's not the problem, a clean one is not going to hurt.

We have a very detailed step-by-step in the Articles section, take a look-see.
That's what happen to me. I got a "dirty throttle body" code and then I noticed that at idle the volts went down to about 10-11, which it has never done before. The truck ran great otherwise. I had my mech clean it, took the ground off the battery overnight to turn the SES light off and everything was fine.
 
1 - 14 of 14 Posts
Top