Service Engine and Reduce Engine Power lights

[hawkeye405]

About a year ago, my battery drained over last winter and I replaced it with a new battery. That's when all the problems began. my truck has 96000 miles on it and I've purchased it new. Then it began ... I got in the truck in the morning on my way to work, I turned the key and nothoing, not a sound. The dash lights came on as did the headlights and radio but it did not crank at all. eventually, i had it towed to the dealer. Their tech worked on the truck for 4 days. he tore out my autostart because he said there was a short in it (they guy who installed the autostart used a resistor instead of a $100 key). The tech then replaced the ignition module and ran new wires where the autostart was spliced in and when that didn't work, he replaced my PCM. Two weeks later, the SES light and the RES lights came on and my truch stalled on the expressway during rush hour. I tried to restart the truck and it would not turn over. I tried again and it started but the lights were still on. I replaced the throttle body and it ran fine for two weeks then both lights came back on. I replaced the accelerator pedal with module and it ran fine for a few days then the lights came back on. Diagnostics show a P1512 code and a P1515 code. I need help.

 

[Mooseman]

You sure you have the right code? P1512 does not exist for GM.

For the P1515, since you replaced the throttle body, the only other thing is the Accelerator pedal sensor unless it's a wiring issue but that error says specifically it's a performance issue, not a connection issue. Could try replacing it.

 

[mrrsm]

The system in question is the TAC (Throttle Control Actuator) composed of three components... any or all of which might be the cause of the problem:

(1) The PCM
(2) The Throttle Body and its internal sub-components
(3) Th ACC Pedal Actuator device

If the Throttle Body was cleaned or R&Rd and and the requisite 30 Minute period of the Battery being disconnected was not done... the TB relearning needed would not have taken place. Since you installed a Brand New Throttle Body... if the new unit you purchased was dropped and there is hidden internal physical damage to the Throttle Body Butterfly Plate, motor or gears and later sold to you as new... but one that was a returned item at the point of purchase ... the TAC system can fail. If the "Gas Pedal" substitute sensor has malfunctioned... the TAC system will fail...This ACC device has several optional replacements... including Dorman... but using only the OEM flavor is the best choice. If the PCM itself is failing ...the TAC system can fail. If a there are any cuts or damage to in any of the wiring, harnesses or connectors... including actions taken by installation techs and mechanics... the TAC system can fail.

 

[hawkeye405]

Mooseman, that code could have been P1516.

MRRSM, I purchased the oem throttle body and from Rock Auto and it arrived sealed and very clean. Since I didn't move the butterfly, I didn't think it was necessary to do the relearn. I did pull the two fuses I think 10 and 28 while replacing the throttle body. The lights turned off for several days then came on so I replaced the accelerator pedal with a brand new OEM one. The lights went off for sevreal days and came on again. Now it's at the dealer.

 

[AtlWrk]

Check out this: http://www.underhoodservice.com/throttle-by-wire-codes-p1512/

Sounds like your symptoms exactly.

Wasn't the throttle body, accelerator pedal or PCM, but an issue with the circuit supplying power to that particular portion of the PCM--there isn't 1 single power supply for the whole PCM, but several dedicated to subsystems within the PCM, all on circuits with dedicated fuses. With all the monkeying around that's been done in your truck's electrical system it wouldn't be hard to believe one got screwed up along the way.

 

[hawkeye405]

Check out this: http://www.underhoodservice.com/throttle-by-wire-codes-p1512/

Sounds like your symptoms exactly.

Wasn't the throttle body, accelerator pedal or PCM, but an issue with the circuit supplying power to that particular portion of the PCM--there isn't 1 single power supply for the whole PCM, but several dedicated to subsystems within the PCM, all on circuits with dedicated fuses. With all the monkeying around that's been done in your truck's electrical system it wouldn't be hard to believe one got screwed up along the way.

So there is a P1512 code which points to a throttle body relearn that I didn't perform.
I just called the chevy service guy and he said that the tech is having problems programing the PCM, again, like when they installed it as new. I wish that I would have waited on bringing it in and read your reply. There was also a blue/white wire that was hanging by the furthest PCM connector after the PCM was installed. I mentioned that to the service guy but he said that the tech told him it has nothing to do with my problems. I'll have to wait till tomorrow to see the outcome.

thanks guys.

 

[AtlWrk]

If it was a wire added for the remote start and then just clipped during its removal then it may very well have nothing to do with your current issues. If it's an OEM wire hanging disconnected from the PCM...well, these tend to be less optional.

Having a remote start installed, then removed, and then the harness "repaired" pretty much means all bets are off regarding the integrity of your wiring harness(es). Wires that have had their insulation damaged or removed (for tapping in a remote system for example), particularly in the engine bay, will corrode if not properly sealed--every day electrical tape won't cut it.

As you can guess, I'm strongly leaning towards damaged wire(s) causing a fault either in the power supply to the PCM or between the PCM and throttle body and/or accelerator pedal circuits. I would suspect the first (power to PCM) because several come directly from the ignition switch and those are the things that get messed with when installing a remote start.

 

[hawkeye405]

If it was a wire added for the remote start and then just clipped during its removal then it may very well have nothing to do with your current issues. If it's an OEM wire hanging disconnected from the PCM...well, these tend to be less optional.

Having a remote start installed, then removed, and then the harness "repaired" pretty much means all bets are off regarding the integrity of your wiring harness(es). Wires that have had their insulation damaged or removed (for tapping in a remote system for example), particularly in the engine bay, will corrode if not properly sealed--every day electrical tape won't cut it.

As you can guess, I'm strongly leaning towards damaged wire(s) causing a fault either in the power supply to the PCM or between the PCM and throttle body and/or accelerator pedal circuits. I would suspect the first (power to PCM) because several come directly from the ignition switch and those are the things that get messed with when installing a remote start.

If it was a wire added for the remote start and then just clipped during its removal then it may very well have nothing to do with your current issues. If it's an OEM wire hanging disconnected from the PCM...well, these tend to be less optional.

Having a remote start installed, then removed, and then the harness "repaired" pretty much means all bets are off regarding the integrity of your wiring harness(es). Wires that have had their insulation damaged or removed (for tapping in a remote system for example), particularly in the engine bay, will corrode if not properly sealed--every day electrical tape won't cut it.

As you can guess, I'm strongly leaning towards damaged wire(s) causing a fault either in the power supply to the PCM or between the PCM and throttle body and/or accelerator pedal circuits. I would suspect the first (power to PCM) because several come directly from the ignition switch and those are the things that get messed with when installing a remote start.

I received a call from the service guy and he told me that the AC Delco OEM throttle body that I installed was not OEM. His tech wasn't able to locate the numbers that were stampped on the side of the throttle body. They installed and programmed a new throttle body and the truck runs like a champ without any issues or error codes. So, he's telling me that the throttle body I purchased from Rockauto wasn't an OEM version. I told him that it's funny cause when I installed this throttle body from RockAuto, the truck ran like a champ also but for a few days only. So I guess I'll have to wait and see. I purchased many parts from RockAuto without any issues before.

 

[AtlWrk]

Looking back over everything:
You have a new PCM, new throttle body (x2) and new accelerator pedal.
Did you pull the fuses or disconnect the battery when you replaced the accelerator pedal? If so, a PCM reset (one way or another) seems to be the thing that gets you back running for a few days/weeks (good to know in case you get stranded again). What, exactly, was the difficulty in programming the PCM? Connection issues perhaps?

Now that you're running again do you have the option of going to another garage or dealer? I only ask because a lot of what your tech is saying doesn't give me a whole lot of confidence. I don't want to be 'that guy' but you need someone who is willing and capable of properly troubleshooting a tricky electrical issue.

The checklist for troubleshooting P1516 (related, even if not the exact code you have) is surprisingly thorough in what exactly needs to be checked and how: power, grounds, opens, shorts, high resistance on all the relevant circuits. That last one could prove important in your case because it can fool you into thinking you have a connection when checked with a meter but it can't support any current when it's needed to drive a motor (like the TAC) or light, for example.

Also, note that replacing the PCM and throttle body are the last things on that list

 

[hawkeye405]

Looking back over everything:
You have a new PCM, new throttle body (x2) and new accelerator pedal.
Did you pull the fuses or disconnect the battery when you replaced the accelerator pedal? If so, a PCM reset (one way or another) seems to be the thing that gets you back running for a few days/weeks (good to know in case you get stranded again). What, exactly, was the difficulty in programming the PCM? Connection issues perhaps?

Now that you're running again do you have the option of going to another garage or dealer? I only ask because a lot of what your tech is saying doesn't give me a whole lot of confidence. I don't want to be 'that guy' but you need someone who is willing and capable of properly troubleshooting a tricky electrical issue.

The checklist for troubleshooting P1516 (related, even if not the exact code you have) is surprisingly thorough in what exactly needs to be checked and how: power, grounds, opens, shorts, high resistance on all the relevant circuits. That last one could prove important in your case because it can fool you into thinking you have a connection when checked with a meter but it can't support any current when it's needed to drive a motor (like the TAC) or light, for example.

Also, note that replacing the PCM and throttle body are the last things on that list

When the dealer tech tried programming the PCM it would start the download and half way through, it would stop. The teck eventually contacted the GM Tech center and they helped with the download. This PCM was replaced because it was causing the GM lockout on the truck (cut power to fuel pump and starter) and that issue was solved.

Yes, every time I have worked on anything electrical, I would pull fuse 10 and 28 and disconnect the negative battery cable. I did the throttle body relearn a few years back after cleaning the throttle body and moving the butterfly but that was the only time I needed to do that. I wish that I had more time to work on the truck but police officer, on afternoons doesn't give me enough time (I also don"t have access to my garage).

I got my truck back and this issue has not come back. RockAuto is giving my credit for the throttle body I purchased from them so for now, all is good.

thanks for the replies and the help.

 

[hawkeye405]

So, having my truck back and running, I saw my old throttle body that the tech took off. I removed it from the rag it was wrapped in and decided to check the part numbers to see if the service guy was right. There was an engraving on top of the body that must have been engraved by RockAuto and GM which is in the casting. That tells me it is a GM part. Then I noticed numbers on the bottom casting that were engraved into the casting its self just like the GM was. I reserched those numbers which are 12 568 580 and it turns out that this is an OEM part for my trailblazer. Now I'm betting that all I had to do is a throttle body relearn and my truck would have been fine. Now what recourse do I have towards this Chevy Dealer Service Tech???

 

[mrrsm]

As fellow LEO (retired since 1999)... it is worth mentioning that your experience with investigations will well and truly help you here. GM is under no obligation to underwrite any component that has been re-built or otherwise modified in any manner. RockAuto will not fight you about the returned most components and that lets them off the hook...and while it might be nice if they would have advised you that the component which originated as an OEM Part has since been re-built with other than OEM verified sub-components... it is probably written in fine print somewhere on their site. It truly is a shame that these GM machines have been manufactured with components that leave very little room for performance variation with other than "Their Own Gear".

The other issue facing you is that more than one component was involved in sorting out the problems with your vehicle...and when it comes to having to get repairs done at any Dealership... they have a lot of hungry mouths to feed and every single thing they do is set up with "Las Vegas Rules" that the famous Mathematician John Nash would explain as " The House Always Wins". So you might spend a great deal of time and energy trying to find some justice and recompense from two companies that will invariably point fingers at one another and not be able to get satisfaction from either one.

You are justifiably angry and disappointed right now... so for whatever this idea is worth... If you keep coming back here to GMT Nation and Read-Learn-Do the things the Members and Historical Repair Documentation have to offer... eventually... You WILL get your money back... and the Consolation Prize will be that in each and every instance... "The Stealerships"... will not be getting their fingers into your wallet. They lose a lot of money when people like us band together, share ideas and fixes and help each other out. Enjoy the Ride...

 

[hawkeye405]

Well put MRRSM. Unfortunately, I will not let the stealership take advantage of me or should I say make an idiot of me, that's just the way I am. The owner will see me first thing Monday. I just can't give in without having my say,

 

[hawkeye405]

The Stealer ship manager told me my throttle body was defective and the cause of this problem. So I started my drive to work and I was on I94 headed south in the reversible express lanes doing 75 when all of a sudden, those lights came on and my speed plummeted down to 20 mph. I finally made it to work and I'm now waiting for the service manager to call me.
The same Service Engine and Reduce Engine Power lights are back on.

 

[mrrsm]

If “The Stealership” Techs cannot sort out the remaining issues… I’d suggest getting the All-Data Repair Procedures so you can figure out every single place that the After-Market Mechs “touched" or put their hands on with the wiring or the follow up by the GM Techs to fix the Auto-Start repair and identify which harnesses they finagled with during their repair procedures.

The idea here is to try and narrow down where you will have to investigate problematic wiring and unwrap all that Black Taping done at the GM Dealership. After that… You can conduct a thorough “Broken Circuit Wire Trace” on the involved harnesses. It would be a breeze to do this repair if you had something like the ECT-2000 Broken Circuit Wireless Probe for this would be a neat trick ...if only it was not so damned expensive.

Now bear with me here ...because while this two part GM Truck "Reduced Power Case Study" involves a Big V8... its the procedures that the VOP Video Original Poster follows and the use of a Wireless Broken Circuit Tool in Part 2 of this Diagnostic that are well worth watching because you might have to resort to doing something like these actions to figure things out. It does NOT matter that you don't have either a Tech-2 or his fancy Snap-On Verus Scanner High $$$ devices... you will see what he does in Part 2 that makes all the difference.

Part 1

Part 2

...and "The Toy" the VOP used in Part 2 to find out exactly what was wrong due to hidden FUBARed After-Market Wiring:

 

[hawkeye405]

Awesome writeup, thanks. I'll check the Web for a ECT 2000 and get a price.

I'll go back with some info on how this started. One day I got into my truck and turned the key an all the dash lights came on but the truck wouldn't crank at all. I checked the battery and it was at 12.9 v. I ran a hot wire from the battery to the + on the starter and it cranked but wouldn't start. I checked to the throttle body connector and all the terminals were clean. I then noticed that after removing the key from the ignition, the security liget on the dash stayed on. I did a lot of research on that and found information that this was the GM Security lockout and only the dealer can reset it. I had the truck towed to the closest Chevy dealer. The truck started for them and they weren't able to recreate the issue. I pick the truck up. The next morning, same thing happened. Towed it to the dealer. They then said the auto start was shorted and they cut out the key module. I took the truck home, next morning it did it again. This time the dealer replaced the PCM and removed the auto start and repaired all the wiring that was spliced. Took the truck home and it starated fine for a week. Then while driving to and the current issue began, service engine and reduce engine power. I stopped at an auto parts store and he checked the codes. P 1515 and P 1512 were the codes that came up. So I replaced the parts above. Now, the dealer has it back this morning and I suggested that they need to replace the PCM that they installed. So I'll know more in a few days.

 

[m.mcmillen]

I have this kit here:

https://www.jbtoolsales.com/power-p...bo-test-kit/?gclid=CP3km42E_9ECFQKNaQodaOYGBw

It has been a life saver many times.

 

[mrrsm]

Let's hope they can finally solve the issues for good and all. But if not... Assuming that the 'autostart' remote system you first tried is referring to the after-market company called 'Autostart'... I thought it might be worth a review of a 2004 Envoy that was being filmed during the removal of an older Autostart set of components, wiring connectors and harnesses while being replaced with another after-market unit, ostensibly better and more modern, etc.

But what is important for the viewer here is that we get to see the terrible conditions of all the wire connections that have an assortment of mating up patchworks of non-soldered squeeze or crimp connectors and harness attachments that look like a serious invitation for creating loose, sketchy and intermittent connections that are at the heart of the ignition switch and power connections. And so this might bear a very thorough going over by you should the Dealership continue their trending pattern of letting you down.

I would not be a bit surprised if all the Techs that have thus far been assigned to work on your vehicle would take one look at all that tangled mess down there and not know any more about it than the average mechanic would. So for what its worth... at least we can get a good look at what these guys have been messing with down there and imagine that a careful examination of each and every connection, supported by cross-referencing the GM Wiring Diagrams of all that stuff would assist you in figuring out where the hidden electrical problems might be hiding:

 

[AtlWrk]

But what is important for the viewer here is that we get to see the terrible conditions of all the wire connections that have an assortment of mating up patchworks of non-soldered squeeze connectors and harness attachments that look like a serious invitation for creating loose, sketchy and intermittent connections that are at the heart of the ignition switch and power connections. And so this might bear a very thorough going over by you should the Dealership continue their trending pattern of letting you down.

FWIW: I bought my trailblazer with 30k. The original owner had obviously installed and since removed a remote start. The wires under the steering column were a mess. All the major power wires going to/from the ignition switch and a few others like the pass lock signal all had huge chunks of insulation missing, conductors twisted and exposed, electrical taped over that had since dried and started to peel off (the stuff really is useless). Wires in other locations under the dash and under the hood were simply snipped off and left hanging Point being, it was a mess.

So I'm curious to see just how the dealer techs "repaired" your harness: electrical tape to hide all the damage, or cut out the damaged parts, solder in new wires and heat shrink over?

If, like on mine, the majority of the damage was directly under the steering column (which is likely, since this is the most accessible place for tapping into them) then you might consider replacing that portion of the harness. I found a used one in good condition on ebay for cheap that I needed as part of another mod. I know you've already thrown a ton of money and parts at the problem but this may worth it since the dealers troubleshooting skills are obviously suspect. You're looking for the clockspring/steering column harness like this (just to show you what I'm talking about):
http://rover.ebay.com/rover/1/711-5...0001&campid=5338077216&icep_item=231523085624

You'll have to do some research for your year, make and options etc to find the exact part you'd need. The key to look for is to make sure it has the big black block connector (called C201) with the screw in the middle.

Big EDIT: Forgot to mention: I missed it in your post #10 but the passlock signal wire I mentioned was what was causing your security lockout condition. This is a signal provided by a little module in the ignition switch key cylinder that tells the PCM that a proper key was used to turn the ignition (as opposed to a screwdriver). A remote start taps into this to fake the signal. If the PCM doesn't see the proper signal it will disable the fuel pump and starter as you saw. The remote start install damaged this wire or was malfunctioning and corrupting the signal. Removing it was what fixed the lockout condition, NOT replacing the PCM which was unnecessary. The signal provided by the lock cylinder is unique to IT, not the PCM which is why you usually need to do a "security relearn" if you replace the PCM (or lock cylinder receiver--exceptionally rare). This doesn't require a dealer, many of us have done it in our driveways when we've replaced our PCMs (for tunes, or other reasons). Replacing your steering column harness will also replace this wire (just the wire, not the security module, so no worries about needing to do a security relearn).

 

[hawkeye405]

OMG, all this fantastic info from you guys, I really appreciate it. I just wish that I had another car to drive back and forth to work so that I can do these repairs.

The service guy just called me and said the truck is ready. They had to replace the PCM again. When I initially replaced the ignition module, I saw how the tech left all the wiring. It was a mess. The 4 black wires that I saw just cut off must have been the ones going to the power door locks because I no longer have the power locks working. The wiring in the steering column were a mess. The insulation one a wire was stripped and another wire was wrapped in that soot and taped. That went on in a few a few spots. I need to figure out how to post pics here.

 

[C-ya]

@hawkeye405 , hope the repair works out for you. I know I would be mad to keep having the same thing happen over and over when it was supposed to be "fixed".

To post pics, use a remote hosting site like Photobucket or the like. Upload your picture and then copy & paste a code from that site into your post. That will link your picture without using up any server space here.

 

[AtlWrk]

The service guy just called me and said the truck is ready. They had to replace the PCM again.

I can't roll my eyes hard enough at this.

I need to figure out how to post pics here.

This would be helpful indeed!
(You can use the "Upload a File" link next to the reply buttons (there are size limitations) or link to a third party hosting site.)

You mentioned a stray wire near the PCM, can you trace it back to where it's connected?
Anything else under the hood seem out place?

The only thing now that sticks out is the part about being able to start the truck after a few minutes...not behavior you'd expect from an intermittent wiring issue...

 

[AtlWrk]

The only thing now that sticks out is the part about being able to start the truck after a few minutes...not behavior you'd expect from an intermittent wiring issue...

So I have a theory:
Somewhere in the wires to and from the ignition switch (the "big 7" wires) or the ignition switch itself you have a weak connection that is overheating. Could be broken strands in the wire, loose or corroded terminals, bad repair job, etc. When it overheats it increases the resistance further, dropping the voltage in the circuit the PCM uses to control the throttle body to the point that it can no longer compensate enough triggering REP mode. After you sit for a few minutes and everything has cooled down a little things seemingly go back to normal. Those wires power many of the subsystems in the truck directly and carry a lot of current--a little increase in resistance therefore results in a proportionally bigger voltage drop. If or how quickly this happens depends on what else is being powered and for how long.

Explains your symptoms and we know those wires have been messed with a lot. A thorough, low-ohm check of all the wires and connections and measuring the voltage on those wires at the C201 connector with the truck running may point you to the weak connection. The other option is just replacing the harness outright (post #19).

 

[hawkeye405]

So, after having the truck for a few days, the Stealerships #1 Tech decided that the PCM they installed went bad again and that my installing a new OE throttle body had caused this issue because I didn't program the throttle body to the PCM and therefore it caused a short in the new PCM. They installed a new PCM and the tech drove it home and several times during the weekend to see if the issue would come up again.

I asked if they tried the new PCM with my new throttle body and the service guy said they did and the throttle body was still bad. I also-ran asked them to repair the auto door locks that came with the truck when I purchased it new and he said no because they would draw too much current and would short the PCM.

I've had the truck now for a week and the only issues that come up are the Service 4WD light every now and then and the truck alarm comes on once in a while when I use the key to unlock the driver side door (the only place for a key entry).

Does anybody know how I can get the auto locks working again after the tech cut the module out and tossed it?

 

[Mooseman]

What utter bullshit! There is no programming of the TB to the PCM. And it was an OEM too. They're just covering their own screw up! There is a very slim change the TB was bad but I doubt it very much.

Auto door locks? You mean when it locks/unlocks when you put it in gear/park? It is run by the BCM. There is no extra module unless there was one with the remote starter. Go through the options on the DIC and activate it. Should be there.

The the 4x4 light coming on, you'd have to be able to read the code when the light is on. Also depends on what is happening when it comes on. Maybe start a thread on that specific issue.

 

[hawkeye405]

Auto door locks? You mean when it locks/unlocks when you put it in gear/park? It is run by the BCM. There is no extra module unless there was one with the remote starter. Go through the options on the DIC and activate it. Should be there.

I was refering to the key fob for entry into the vehicle. I had it when I bought the truck new in 03. It stopped working after the dealers tech tore out the remote start unit and its components and tossed them into the trash.

 

[Mooseman]

It should still work. That's done by the lift gate module unless it was programmed out of the LGM and BCM. Who installed the remote starter? If it was the dealer, it wouldn't surprise me if they removed that option at the time.

 

[hawkeye405]

It should still work. That's done by the lift gate module unless it was programmed out of the LGM and BCM. Who installed the remote starter? If it was the dealer, it wouldn't surprise me if they removed that option at the time.

I had the remote starter installed back in 2003 by an installer at one of those stereo places. It worked fine up until this issue when the dealer ripped it out and then charged me $220 to repair the wiring in the column. I did see 4 thin black stranded wires coming out from the drivers side left kick panel. I just taped them up.