Weird problem with Brake light and OBDII

Simple facts:

I replaced the cold air intake, cleaned the MAF with MAF sensor cleaner, replaced EGR Valve, and forgot to reconnect the MAF sensor for 1 day. The next day after I caught my oversight, I took the battery cable off to reset codes, etc. and reconnected MAF plug and battery connections..... Then.....

Next day I get Battery light :-( I had 10 month old upgraded alternator and 1 year old battery.

So check everything and alternator tests bad, battery tested good, so I replaced alternator.

Battery light still on. So I recheck battery it tests bad just 2 days after testing good!

Replace battery, and battery light is still on.

Go to Autozone to test alternator and battery again, everything checks out ok, so I asked them to check the OBDII codes, and MY OBDII plug has NO power to it!

So I have a battery light and no power to OBDII plug, all fuses looked ok, and battery/alternator are testing ok.....

Check the horn fuse in the interior fuse panel, that supplies power to the obd port.

Also there is a rubber or plastic boot that isolates the positive post on the alternator from the housing (ground). If thats cracked or missing you will get a good sized electrical short. That would also explain why the fuse for the horn/obd port blew. Alternators are really sensitive to short circuit so it may also blow your new alternator if thats the issue, or another short somewhere between the battery, alternator and fuse box.

I'm not surprised the battery went right after the altermator, a bad alternator puts tons of stress on a battery either by overcharging and causing dryout or an internal short, or over discharging and causing a cell to reverse polarity.


The battery light can also be caused by a poor reading from the alternator, so when it was replaced a loose connection, or broken wire at the connector.

Good luck!

How about your belt tensioner? If thats going you may not be getting quite enough out of your alternator. if you have a volt meter you can check the voltage at the battery yourself, when everything is off your battery should be around 12.6-12.8. When the engine is running you should be around 13.6-14.0. The battery light will also come on if you are over or over a normal voltage range. If you are under your abs light, and brake light will sometimes come on. If you are way over your check engine light will come on.

Ryan.....maybe a short in your computer?

Quote:

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Originally Posted by etlsport

Check the horn fuse in the interior fuse panel, that supplies power to the obd port.

Also there is a rubber or plastic boot that isolates the positive post on the alternator from the housing (ground).

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I will check but the horn is working perfectly.

I installed the alternator myself and everything is great under there.

Quote:

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Originally Posted by etlsport

How about your belt tensioner? If thats going you may not be getting quite enough out of your alternator. if you have a volt meter you can check the voltage at the battery yourself, when everything is off your battery should be around 12.6-12.8. When the engine is running you should be around 13.6-14.0. The battery light will also come on if you are over or over a normal voltage range. If you are under your abs light, and brake light will sometimes come on. If you are way over your check engine light will come on.

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I have had problems with the belt tensioner in the past, but I am getting 13.8 consistently when running.

Quote:

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Originally Posted by VX crazy

Ryan.....maybe a short in your computer?

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Yeah that is what I was thinking, I just have no idea how/why or how to fix it :-(

How was the brake light related to the problem you were having? What does it do/not do?

I was getting valve clatter because of incorrect back pressure, and thus changing the EGR valve should have helped, but it seems that it was more like I needed to do the EGR cleaning thing, and I did that today and it seems to have helped a ton!

So right now only problems that I can see:
-obdii does not have any power to it
-brake light is constantly on

We will see if valve clatter and back pressure issue is resolved, I have tried everything so far:
-tune up with new valve cover gaskets and plugs
-new timing belt/tensioner/bearings/water pump
-new EGR valve and gasket

I really hope this is not just a sticking lifter like so many 3.5's develop. I called the local shop that solely deals with engine removal and rebuilding/reinstallation and he said that Isuzu 3.5's are known for failed lifters.

Mark, maybe I heard wrong from the guy but I thought that is what he said, but then again he was the guy answering the phone and admitted he never worked in the shop.

When I had the valve gaskets replaced and tune up done I asked the mechanic to check the valves to see if they need adjustment, but he said everything looked fine, but I doubt he checked at all. I will call them back and talk to the owner I know him pretty well and is a honest guy.

Is there a place where I can read up on or print out a how to for me (or the mechanic) to check the valves and adjust them? Is this in our manual? Thanks!

I am still having the valve clatter problem, but it is now only after I have been driving for a while. I can always tell when it is going to do it because everytime I let my foot off the gas the RPM's drop all the way to 500rpm and then bounce back up over 1k like they should while driving, the TOD doesn't know what to do when this happens either and normally I get a flash of all 3 lights on TOD, and this is when I am getting the valve clatter only.

But the battery light is still on and I still have no OBDII..... I am getting very frustrated with the VX. I have done nothing but pour money into it trying to make it a reliable ride and things keep happening!!!!!

I can admit it, I'm at something of a loss on this one, although I keep coming back to the solid state EBCM (Electronic Brake control Module) for some reason.

Out of curiosity, is your EB-13 (20A ABS fuse) blown?

I don't know I will check

All fuses are ok, but now VX will not go further than 80-100 miles before shutting engine down. I have been stranded on the side of the road 3 times in the last 4 days. If you let it sit for a while and then unPlug the MAF sensor and the EGR valve then it will run again, but will still sometimes cut engine out still.