Chasing gremlins

[redline customs]

I've got a 4.2 I 6 03 tb. I just replaced the engine about 2k ago. I've had a few problems that got fixed(loose grounds). A few days ago, I got to work, sat for about ten mins, and the battery was dead. Didn't have anything running. Figured the batt was just bad so I went and got another. Came out this morning and dead too. Jumped it. Ran long enough to get it charged, stated charged for a while, but I could hear something running. Figured out it was the throttle body. Its making some kind of whining noise.After a few seconds(15-30) it will make a different noise, and one of the relays will click, then goes back to it. It kinda feels like a fuel pump relay, but may be the vibrations going through the fuse box. It only stops if I unhook the battery, or the PCM fuse.I didn't see any broken or frayed wiring but I haven't been able to follow it all the way. Also the check engine light will stay on after I turn the key off And remove it.occasionally the security light will come on also.

I took it to O'Reillys earlier and they tested the alternator, told me voltage regulator was bad. I had a spare alt that came with the new motor, so I slapped that on there. Charges fine(seems to anyways), but the noise is still present. I also had a spare throttle body( also on the replacement motor) so I hooked that up(just the plug not actually mounting it) and still It goes on. Didn't change the deal with the security or cel though. I'm wondering if maybe the bad voltage regulator may have spiked and shorted out the PCM? No driveability problems when it starts though so idk. Any suggestions?

Edit: also seems that the fan clutch stopped releasing. Friggin loud as hell if it can be heard over my side dumped straight pipe. Can I unhook the plug and it stay released or is it normally closed? I'm running with no hood and temp doesn't get above the first big line unless I'm idling and even then its only about halfway to 210 from the first line(160?) So the fan isn't a big problem if its not running. Killed my mileage though(used a quarter tank in about 30 miles)

 

[Mooseman]

What is the code for the CEL?

Just a hunch, try disconnecting the fan clutch. Some have been known to go bad and mess up the 5v signal.

 

[redline customs]

Oddly enough the only code that comes up is for abs. That's what O'Reilly pulled anyway. I'd check myself but I let my step dad use my scanner and haven't gone to get it yet. I didn't think that abs would set the check engine light. May be wrong but I thought it had its own light? Alsp the cel is not new, its been on since the swap, but it is new for it to stay on even after the key is off and removed. I'm assuming that its not on some kind of timer since it was on this morning and I hadn't driven in about 10- 12 hours.

 

[mrrsm]

You are right about this one being a "Real Gremlin"... and the culprit in this case is Short Circuited Secondary Air Injection Pump Relay located way down on the SUV sub-frame. What can happen over time is that this relay will clog with water (Sea Water is the worst if the vehicle has been used to drive boats in and out of boat ramps) and after filling up with water...the Electrical Connections will corrode enough to bypass the Relay and short circuit the SAIP.

When the juice is flowing... the Pump on the engine will run down the battery and the clicking happens when there is no more "juice" to power. Its proximity to the Throttle Body is such that the Air Resonator will pick up the sound and make it seem like the Throttle Body is The Bad Guy. Its a PITA Fix... but it might be time to invest in replacing both the SAIP itself on the engine as well as the SAIP Relay because running continuously like this can damage the motor.

http://www.tonkinonlineparts.com/showAssembly.aspx?ukey_assembly=815189

 

[redline customs]

I would say that this COULD be the problem, but I don't have sais. The "new" motor had it, but as mine didn't, and I couldn't find any wiring for it, I just removed the pump and used the block off plate from the original motor. Also I am 100% certain that it is the throttle body making the noise since I put the other one on and hooked up the wiring. I put my finger on the butterfly and can feel that it is vibrating in time with the whining. If I pull the PCM b fuse(number ten in underhood fuse box), it stops(which is why I am suspecting faulty PCM.) Also discovered that the middle plug on the PCM(gray cap) will stop the noise when unhooked from pcm. There is also I slight browning on the bottom most portion of the plug that extends about 3 or 4 pin holes up. I checked the wiring carefully around this area and on this plug and still cannot find any breaks or burning/melting on the wiring. Anybody have a pin out for the plugs on the PCM so I can see if that area coinsides with the throttle body/cel wiring? To me it either seems that the PCM is faulty and constantly running, or some wires are burnt somewhere and contacting with a constant power source. I wouldn't think that the latter would be the case, unless the constant power in question is the actual power for the PCM, or one that is controlled by the PCM fuse.

 

[mrrsm]

That makes perfect sense because several other members have reported that after making an Engine Swap... and having Loose Ground Wires present after the PCM was hooked up and Battery Power was applied... subsequently... their PCMs got Wonky and had to be replaced... probably because of Arcing Ground Wire Connections. There are a few available right now on ebay:

http://www.ebay.com/sch/i.html?_fro...m.TRS0&_nkw=2003+trainlazer+4.2l+pcm&_sacat=0

@redline customs

Some time back... I loaded the PCM Connector Pin-Out Diagrams at Message #17 of this Post:

http://gmtnation.com/forums/threads/solved-04-trailblazer-lt-4-2-l-no-crank-no-start.14737/

 

[Mooseman]

You could just go to a pick-a-part and get another PCM for the same year and gearing truck. Would be cheap and the only thing you'd need is a security relearn.

 

[littleblazer]

Stupid question but you have anything in the obd2 port? That's left things running on my truck and killed the battery several times.

Edit, forget that, yours is happening too quickly it seems. But I would say something is keeping the PCM from entering sleep mode.

 

[redline customs]

No I don't have anything in the obd port. I would just go get a pcm, but I have yet to find any more trailblazers in a salvage yard around. I had to drive nearly 3 hours just to get the motor. Is it possible that the burn mark on the plug could have allowed two wires to touch? Is there any constant power into the PCM? Like I said, if I pull the PCM fuse, it keeps everything from running. I'm hoping that its just a burnt wire or something.
On another note, if I get a tuned PCM from PCM for less, can I just outright buy one without a core? Or do they refurbish them and can take some that's messed up?

 

[Sparky]

How has nobody mentioned the ignition switch yet?

But seriously, stuff still powered up and lights on the dash with the key out makes me instantly think that switch isn't turning off.

 

[webdawg]

How has nobody mentioned the ignition switch yet?

But seriously, stuff still powered up and lights on the dash with the key out makes me instantly think that switch isn't turning off.

I was going through this post and it was one of the first things I was about to mention.

 

[redline customs]

Any suggestions on how I should go about tackling this? If I unhook the ignition switch will that turn everything off if its the problem? What about testing the PCM? Anyway to do that?

 

[mrrsm]

This recent post covers most of the Ignition Switch "How-To" Diagnostics and R&R information:

http://gmtnation.com/forums/threads/engine-would-not-turn-off.16178/#post-516257