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Discussion Starter · #1 ·
OK, had all kinds of questionable problems, got the reprogrammed PCM, plugged it in and the car was improving. The startup idle is still way too high, but considering that is the only issue, I would be better off leaving it alone.
So, last weekend, the starter goes out. Got the new one ordered from Rock Auto, disconnect the battery, change the starter and all hell breaks loose. Never had these battery gremlins happen on this car with any PCM, except the new one. All the gremlins, the stupid HVAC actuator clicking, ignition key not recognized code on the trans side, 1682 code on engine side, EBCM ground on the antilock brake side.
First start up, not lites on the dash, drive it home, dies halfway. PCM 1 fuse blown. Tow it home before I realized that was all it was. Try to drive it back, PCM 1 fuse blows 2 more times ( only had 15's not 20's) Call the guy that reprogrammed the PCM that worked and they say its probably in the fuse box now. All this happened after the battery was disconnected.
Went thru all the threads here, the wait 90 seconds for the actuators to go thru calibration with switch on, nothing changed. Disconnect battery overnight again, try a second time and no change.
I was thinking just get another flash PCM again and see if it changes anything before I start destroying a wiring harness looking for grounds. Just dont know if (now its snowing and bitter cold) if I should just try to get the 50 miles on the car to allow a full relearn before trying another PCM.
 

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I'm not sure about the what to do with the PCM, but I can tell you that one or more of your HVAC actuators have bit the dust as a result of the battery cable(s) being disconnected. When you reconnected the battery cable(s), that forced the HVAC actuators to run a calibration procedure which stressed the old, brittle nylon gears that are used in the actuators to break.

I know, you had to disconnect the battery cable(s) in order to remover the starter, but had you used some type of Keep Alive Memory device, you likely would not be facing as many difficulties as you are now facing. No, I am not saying "...See, I told you so...", I'm just letting you know what happened and how to prevent it the next time some repair instruction says to disconnect one or both battery cables. I'm facing something similar with my '04 TrailBlazer that's been parked and not run for way longer than I am really comfortable with.

Now back to the other "troubles". With respect to the ignition key, the BCM and ECM need to be forced to talk to one another by doing a new key learning procedure which takes about 30 - 60 minutes. Here it is thanks to another member:

1. Attempt to start the truck by turning the key to the Start/Run position. Try to
crank the vehicle.
2. Observe that the vehicle fails to start and the security light is illuminated.
3. Release key to the ON/RUN position (not the ACC position or OFF)
4. Allow the vehicle to sit with key in the ON/RUN position for no less than 11
minutes. Security light will turn off after this.
5. When the light goes off, turn key to OFF position and allow the vehicle to
remain in the OFF position for no less than 30 seconds.
6. Repeat #1-#5 for four cycles or until vehicle starts.
The P1628 is the code for an Electronic Throttle Control Malfunction. After you perform the ignition key security relearn procedure, remove the fuses from the underhood fuse panel for the throttle body and the PCM power. The fuses are labled PCM1 and PCMB in the owner's manual. Leave them out for at least 30 minutes and then the P1628 should go away.

Good Luck!
 
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Also, fuses blow for a reason.
You've got a short or an overload somewhere.
Start by looking at a wiring diagram of where the wire goes that blows the fuse and carefully follow.
Bigger fuse is not the answer, unless you're looking for melted wire!
You have two completely separate issues here.
Patience, my friend.
 

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Discussion Starter · #4 ·
This is the thing though, (its 1682 not 1628) both ignition key and switch codes point the finger at needing to do the key relearn. There is no security light, and the car cranks fine. When the key relearn was needed with the PCM change, the car will not even crank. Then it was the 10 minutes to security lite off, to on to 10 minutes of security light off, I believe I had to go thru 4 or 5 cycles before it cranked.
This all started because of a taxed starter. Key on and it would turn almost like you needed a shim in an undermount type starter. Drove to work, did not park out of the way of the gate, went to restart and it just would not engage the starter motor again. So yes, go to key start and hold it expecting maybe it would break free and turn might have damaged the switch.
We have to turn to get to our lift, the last time, I was pushing with a forklift, lifted the rear end off the ground and drove it forward to make the turn and the ABS got all confused, but it was a clear code for ABS, did the bleed and it cleared. I cannot clear any of these codes. The EBCM code says it is missing its ground. The computer completes grounds.
We replaced the starter and was just driving fine, our route does not let us go over 35 on the ride home so it might have been in limp mode, I dont know, but was getting to a stoplight and it just died and would not restart, that was when the PCM1 fuse blew the first time. Towed it home (which confuses ABS again) before realizing it was just the fuse. We did alot of work on this thing and after disconnecting the battery multiple times before this PCM was installed, never had any of the gremlins starting with the stupid vent door modulator.
They say the modulator relearn kills a questionable motor, so I will swallow that one, I get defrost so that is all that matters here. But for three more codes to show with no chance of clearing them and letting them reset again, with no check engine light on either is what has me baffled. Codes are there but have not been on enough to lite the check engine light? Which is why a box of fuses and getting thru relearn sounds like the only way to get some explanation.
 

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Discussion Starter · #5 ·
Also, fuses blow for a reason.
You've got a short or an overload somewhere.
Start by looking at a wiring diagram of where the wire goes that blows the fuse and carefully follow.
Bigger fuse is not the answer, unless you're looking for melted wire!
You have two completely separate issues here.
Patience, my friend.
sometimes getting to the melted wire is the fastest way to find the damned thing.
 

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2004 chevy trailblazer_ls
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Sometimes a bad coil will blow fuse 28. A real bitch to find, as the coil will ohm out correctly.
I've read here a PCM could do it too.
 

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Discussion Starter · #7 ·
Sometimes a bad coil will blow fuse 28. A real bitch to find, as the coil will ohm out correctly.
I've read here a PCM could do it too.
that is the bitch about this PCM1, the wires go everywhere, from the fuel pump to the coils to the damned MAF switch. This all started with a coil that blew and ignited a fuel or refrigerant leak. I lit my eyebrows with refrigerant once so I know it burns, and that was the hose to metal tube connection that was right next to the coil that blew. But I would have to have a misfire happening if it were a bad coil, no?
The inability to clear codes has me convinced that the PCM is junk and apparently, has the code burnt into its memory so it cannot be erased. Going to try to find my little OTC scan tool to see if that one could erase the codes while I contemplate getting another PCM flashed.
 

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Discussion Starter · #8 ·
The car just sat and idled for 3 hours. Took it out to the street, went over 35, so no limp mode; I guess. Locked up the brakes and no anti lock Acme Coyote vs roadrunner spring sound, just locked up. Went around a second time, still no trouble. Locked them up from about 50 and the car died, let off the brakes, rolled it into the lot. Got out to change the 28 fuse, it was not blown. ( I am using a 30 because, yeah, burnt wires are easier to find). Got back in and just started up normally with the stupid modulator motor clicking.
 

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First off, my apologies for putting down P1628 instead of P1682. The information about the P16XX code I typed in is for the P1682 code, and hence correct. My dyslexia must have acted up again.

What code scanner/reader are you using to pull codes and are attempting to clear codes with?

What are all the codes you are reading from the OBDII system.

Have you load tested the battery? I do not care if the battery is brand spanking new or several years old. Have it load tested because a bad battery can cause all kinds of strange and annoying problems. Also check the battery cable connections to ground and to the starter to make sure they are clean and tight. Also check the battery cables to make sure they have not corroded under the insulation.

What year is your vehicle and which engine do you have?

When you initially start the engine, does the check engine light come on for several seconds and then go out? Has the Reduced Power light illuminated on you?

Yes, I'm asking a lot of questions. You are there and I am not so I need the information to assist you.

Have you visually examined the wires going to the ABS module and the ground wire to make sure all are as they should be?

Good Luck!
 

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Discussion Starter · #10 ·
First off, my apologies for putting down P1628 instead of P1682. The information about the P16XX code I typed in is for the P1682 code, and hence correct. My dyslexia must have acted up again.

What code scanner/reader are you using to pull codes and are attempting to clear codes with?

What are all the codes you are reading from the OBDII system.

Have you load tested the battery? I do not care if the battery is brand spanking new or several years old. Have it load tested because a bad battery can cause all kinds of strange and annoying problems. Also check the battery cable connections to ground and to the starter to make sure they are clean and tight. Also check the battery cables to make sure they have not corroded under the insulation.

What year is your vehicle and which engine do you have?

When you initially start the engine, does the check engine light come on for several seconds and then go out? Has the Reduced Power light illuminated on you?

Yes, I'm asking a lot of questions. You are there and I am not so I need the information to assist you.

Have you visually examined the wires going to the ABS module and the ground wire to make sure all are as they should be?

Good Luck!
Please do not apologize for trying to help people on this site. I am sorry if I am sounding short with any answers, disconnect a battery 20 times and have no issues, then get problems and read all the reasons you should not disconnect a battery. None of the answers are stated like, Before you disconnect your battery, turn the heater control off, or radio off, or turn the car on and off 30 times before crap, its just never disconnect your battery which is impossible if you are changing a starter.

We have a modis updated to 2009 we use for codes.
The ABS fuse was blown, so changing that the ABS lite went off. Have not checked for the acme coyote spring sound yet.
I know the 1682 code for sure, the transmission section has a code that reads that it does not recognize the ignition key. Do not have that number.
The ABS system has the code that reads, missing ground at EBCM.

I have never seen a lite for low power mode at any time. I have seen a throttle body reset method of letting the car run 3 minutes, off one minute, on three minutes, off one minute and then drive. Did it with a stop watch, no change. I dont even know if that is a real thing.

I understand, the modulator motors get weak and this happens with a battery reconnect almost pointing at an issue. I am just hoping if it is a bad coil that eventually a misfire code would show or the car would start on fire again. This is just the first time we have disconnected a battery with this PCM installed and all hell broke lose.

Its an AGM battery from Rock Auto, Excalibur I believe because all my local stores stopped allowing online discounts for batteries around me, so if I had to pay 170 for a battery, I was going to go AGM. No problem with the battery. I have one of the old load test boxes that remain in the good zone when the switch is triggered.
 

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that is the bitch about this PCM1, the wires go everywhere, from the fuel pump to the coils to the damned MAF switch. This all started with a coil that blew and ignited a fuel or refrigerant leak. I lit my eyebrows with refrigerant once so I know it burns, and that was the hose to metal tube connection that was right next to the coil that blew. But I would have to have a misfire happening if it were a bad coil, no?
The inability to clear codes has me convinced that the PCM is junk and apparently, has the code burnt into its memory so it cannot be erased. Going to try to find my little OTC scan tool to see if that one could erase the codes while I contemplate getting another PCM flashed.
Pardon my ignorance, but you have a MAF? I know my 4.1 does not have a MAF.

What engine is this - and the year - etc?
 

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OK, on using a Snap-on modis for getting the codes.

Just apologizing for my sometimes too big fingers :)

I guess the main question should really be what caused you to install a "new" PCM in the first place. Also, when you moved your TrailBlazer with the forklift, did you inspect the TrailBlazer for damage that might have resulted?

With all of the various apparently electrical problems that occurred all at once, 1- they are likely related to a common issue, and 2 - that issue might be a missing ground connection.
 
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The addition of the MAF sensor to the 4.2 L's ensemble must be a late 2005 model year thing.
 
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Discussion Starter · #16 ·
sorry for the delay. Its the straight 6 4.2 in a 2003 Fully decked out. Go on rock auto you can buy a MAF for the standard only, so some had them. I dont think the LTZ whatever this is had one because they have the stupid drive by wire throttle body that has a mind of its own.

I dont have any answers other than the modulator still clicks for 90 seconds and it took 68.3 miles of driving for the service engine light to go on last night. This is all with the 30 amp still in the PCM1 spot. I will check over the weekend and begging for an ignition or misfire code to point me right to a coil pack.

The only reason I questioned the PCM at the beginning, this reflashed one, was because all the battery disconnects over the 3 months of repairing this thing we never fell into the bag of tricks from disconnecting a battery.

So still no answers, other than looking for a thread to see how much of the dash needs to be gutted to get to the ticker.
 

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I just sent a 2007 TB 4.2 out after repairing a head light .... and it was MAP.

Even my wife's 2005 Silverado 5.3 Z1R is MAP.

The MAP is partly responsible for throttle regulation ... and I know I'm kicking at dead dogs here again ..... but ......

......... by design, the throttle cannot open further than factory computer controlled programming to keep the PCV functioning at least at a minimal capacity so the crankshaft area is going to be purged of moisture and fumes in spite of whatever desires the driver has.

Sometimes ... getting a toon will sidestep this part of the factory's design ... just to satisfy children with cars desires to be able to go WOT when they want to.

It's counterproductive ... and will shorten the life of the engine because you cannot lubricate an engine with water.

The results of a non-operational PCV is water in the lube oil, seized VVT, unnecessary cleaning cycles of the throttle body and cam & follower damage.

NEW MOTTO -------> FIX THE PROBLEM ....... NOT THE SYMPTOMS.
 

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Discussion Starter · #18 ·
well, I will check PCV and anything else. I dont know anything about Toons. I just got a replacement PCM because there was a fire in this engine. I got the replacement harness from the same motor but a 2006. The little differences were neutral safety switch and front O2 connectors. I decided to leave the wires alone and use the 06 parts. Eventually tried to use the 06 PCM and it worked for the most part, but going on the alldata site, there were different connections on the PCM for those two differences, so went back to the pcm I got with it. When the gremlins returned, I then decided to buy a replacement that was flashed to the vin, put the proper connectors on and replaced the 02 and neutral safety switch and it was fine. Everything was good, until the starter gave up and I disconnected the f'n battery. Now the code that came back is not recognizing the ignition key again, but it starts and runs.
 

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well, I will check PCV and anything else. I dont know anything about Toons. I just got a replacement PCM because there was a fire in this engine. I got the replacement harness from the same motor but a 2006. The little differences were neutral safety switch and front O2 connectors. I decided to leave the wires alone and use the 06 parts. Eventually tried to use the 06 PCM and it worked for the most part, but going on the alldata site, there were different connections on the PCM for those two differences, so went back to the pcm I got with it. When the gremlins returned, I then decided to buy a replacement that was flashed to the vin, put the proper connectors on and replaced the 02 and neutral safety switch and it was fine. Everything was good, until the starter gave up and I disconnected the f'n battery. Now the code that came back is not recognizing the ignition key again, but it starts and runs.
There's an incongruity there with a battery disconnect creating all that havoc again.

Yours is one glaring example of what I preach concerning using a KAM so things like this don't happen.

Somewhere I feel you've awakened a sleeping VATS moebius and people like TJ and chem_man are gonna be your guardian angels now.
 
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