I have an '05 Trailblazer L6 with 47K miles.

A month ago I had headlights dim and voltage drop and figured I needed to replace the alternator. I had an independent shop do it, because the local dealer closed.

Afterreplacing it, I got a service engine light with the lights going dim and same voltage drop (below 14v on the gauge). This happened whenI let off the accelerator as the engine was warming up (before the engine got up to 210 degrees on the gauge).

I took it back to theshop and they said it had water in the EGR hose, cleared the codes(don't know what they were) and said try it. Well I did and the symptoms are back.

What am I dealing with? I've not worked on this engine before. I used to have a Grand Am that did this and was a clogged passage between the EGR valve and the back side of the throttle body (intake).

What do you guys think?

KY Blazer [&:]

 

This is a very common problem with the GMT360 platform vehicles. My Rainier would do it a LOT. One thing that the dealer will tell you is to wait after you start your truck. You need to allow up to 30 seconds for the AIR (Air Injection Reaction) system to run its self test. The AIR pump draws a lot of current when it kicks on. If the self test is allowed to complete, I was told that it will soft start (lower speed, lower current draw), but if the test is cut short, it will kick on full speed whenever you are coasting. Due to the computer controlled regulators in these alternators, the PCM cannot adjust the alternator output fast enough to overcome the draw.

I was able to stabilize the voltage a lot more by wiring in new grounds from the battery to the frame and then over to the engine block. Once spring gets here, I am going to grab a junkyard alternator and see what I can find after disassembling it. I have not run a new positive cable to the alternator yet, but I am planning on it when I replace my thermostat, which is coming up soon.

Not the best of outlook for you, but I can definitely feel your pain.

Concerning the CEL, have you had the code read? If so, what was it?

 

If swarts answer doesn't pan out.

Typically dim lights indicate a ground problem. Check your negative cable for corrosion at the battery, cable, block, frame connections.

 

That was the first thing I thought too Tim, but my truck still does it. It is much worse when you just jump in and drive.

 

I've had it to an idependent shop twice (dealer out of business)and they replaced the secondary air injection pump. I took the vehicle back and got a svc. engine light again and when I took it back they finally came up with technical service bulletin 06-06-04-017 that is for the revised pipe placement for the tubing going to the pump.

Then the shop owner tells me what a turd the Trailblazers are and agrees to finish the job on a call back with no additional charge this coming week (parts on order). He printed off a list of the TSB's and there are over 100 of them! Are we driving GM junque? [&o]

 

Look at any vehicle, GM or otherwise, and you will see a laundry list of TSBs. They are just documents to help technicians identify specific problems.

The light dimming issue is a annoying one for sure, but I would not call these vehicles "turds" or "junque".

 

Actually the light dimming isnot an issueexcept when the pump starts, and if what the shop is telling me is valid, will be solved when they replace the tubing in the TSB.

I'vedone my own mechanic work (brakes, o/c, general service) for a long time except for electronic stuff where you need an analyzer.Hell I work on my own airplane and can't fix my cars anymore!! I was trying to get an ideaif this type vehicle (or platform) is more ofa "garage queen" than other SUV's, or if the shop owner is just pissed off for having to do a call back on my Blazer b/c one of his mechanics didn't research theproblemb4 throwing parts at it??

I'd like to find out I can drive this thing for a few years before it starts hitting me in the bank account.

I love how it goes on snow & ice and the hwy mileage is around 18mpg if I don't lean on it too much.

Thanks,

KYBlaze

 

The problem with many mechanics opinion is that it is only based on vehicles which have had problems and is no where near indicative of the product line as a whole. Considering that a local shop may see not even 0.01% of the entire production lot of a certain model, it is difficult for them to be able to classify one model as junk over any other. Not to mention that every car manufacturer has lemons every once in awhile which for one shop may skew their view of a vehicles reliability.

I am VERY happy with my Rainier (Buicks version of the Trailblazer), dimming headlights aside. I have the issue with mine even without having a problem with the air pump as many others do as well although it is greatly reduced by allowing the truck to run for 30-40 seconds before putting it into gear. I will be attempting to remedy this issue come spring time once the pick-n-pull yards open back up.

 

I'll let these guys put the tubing on for the TSB and if I still have the lights flickering, I'll see about improving the grounding.

Thanks for the objective response.

I'll post the results.