code P0380????

[Shed]

About 3 weeks ago my oldest boy decided to "help" me out and plug my truck in. Nice, but it only got down to 35 degrees that night. Next day I had an SES light on. Dealer scanned and said it was the plug that "over energized" the system, common LB7 problem, no harm no foul. They reset and all was fine.

3 days ago another SES. Bought a cheap code reader and it reads PO380, something to do with a glow plug CKT. I reset it thinking it was the same code. No the truck has not been plugged in for weeks (I put my cord away to make sure I recieved no more help). My friend at the dealership says that it's not a big deal but if it keeps up to bring it in. Well I clear it and the next start it sets again. The truck is running great, best fuel mileage of the year this past week!

Does anyone have any idea what this is? Or may be? How much is might cost me? Thanks for all your imput, you may jusy lower my stress level!
Shed

[Kennedy]

You'd have to do some troubleshooting of course, but based on an educated guess, I'd say there is a good chance that the glow plug relay is bad

[DmaxMaverick]

Could be one of 3 things. Check in any convenient order:

1. Glow plug(s). Check them for continuity from the power connector stud to body (part that contacts head). Any "open" plugs are bad.

2. Intake heater element. It's in the intake pipe, just before the intake plenum. Large (24mm?) hex with a nut holding the wire onto it. Open=bad.

3. Relays. In the underhood power distribution box (fuse box). They are marked on the diagram legend. The relays are the same as others, so you can switch them around and "test" the other systems for operation. They are common, so you can get a new relay at any chain parts store, like Napa, Autozone, etc.

Try a search for P0380. Lots of threads with good info.

[Shed]

Thanks for the great info again gentlemen! What's a relay or controller cost normally? I'm definately not a mechanic and have very limited electrical expirience so I will have to take it to the dealer. Just figure I can ask them to check some of the stuff you guys have told me about(intake heater, GP controller/relays). Thanks again!!!! Shed

[DmaxMaverick]

Save yourself a BUNCH of money on this. There is NO part that isn't as simple as it gets. The relays (in the underhood power box) aren't too expensive, as long as you don't get them from the dealer. I think the individual relays are about $120 at the dealer, $20 locally. If the heater controller/relay is bad, replace the entire controller assy. It's about $70, while the individual relays are double that.

Try doing the diagnosis yourself. All you need is a test light or multimeter (capable of reading continuity or resistance), and simple tools. Nothing is hidden and there should be no surprises. The dealer will charge you a minimum diagnostic charge, and very likely several charges for "failed attempts" to repair. Not to mention, many of them will try to sell you things like glow plugs (and the labor to install them), just because they think it's time.

At any rate, we can help you. As a last resort, you can still take it to the dealer. This issue is not dangerous and will not cause damage to your truck if it goes on for a while (lets you take your time doing it, over several days if necessary). Unless you are trying to start your engine in sub freezing temps, the whole glow plug and intake heater systems are there to keep the EPA happy, anyway. I've started mine at less than 20°F with the heater and glow plug systems disabled (curiosity). It fired off just fine, only with some smoke and a little more rattle for a few seconds.

[Shed]

Dmax, Thank you for the offer! I honestly have no idea what a relay looks like and the heater is on the intake tube right? I just touch the light tester to what part? and if it lights up it's o.k.? If not, it needs replaced? Not even sure what a relay looks like. I should be able to get these parts at an O'Reilly auto parts store? I apologize for the rapid fire questions. I really need to save the money and appriciate your help! This always happend at the worst times! Basement remodel in full swing! Shed

[Shed]

dmax, I'm lookin at the truck and wondering is the GP relay under the fuse area? It's diagramed on there but looks as though it is off to the left (front) and there is nothing there but a battery/cables for the battery. I really do appriciate all of your help and apologize for having no idea! Shed

[DmaxMaverick]

The controller for the heater and glow plugs is above the rear driver side valve cover. The relays are the 1" cubes in the fuse box. They are labeled on the underside of the box cover. They have a part number on them. You can mix/match the relays with the same numbers. Your auto parts store should have them, or can order them. Take one with you, and they should be able to match one by the number. The relays are industry standard, not specific to GM. They can be tested, but just as easy to switch them with another system (and a lot less technical). If a failure follows the relay, the relay is bad. If the problem stays, the relay is good.

To test the heater element and glow plugs, remove the nut at the end, where the wire attaches. Clip the wire end of your test light to the bat+ terminal (or the red jump start box in front of the brake master cylinder), and probe the end of the heater or glow plug where the wire attached. If the light lights, it's good. If not, it's bad. That simple. Replacement of the heater or glow plugs is the same as replacing a spark plug. Be careful and go slow, though. The glow plugs can, on occasion, break off right where they meet the head. Just go slow and there should be no problem.

If the relays, heater, and all the plugs are good, then the controller needs replacement. It is not hard, just come back if you get that far. Like I said, this is not a critical system, and your truck will run fine with the error and SES lamp on.

[Shed]

Maverick, again THANK YOU! I am work right now (fire station) an will have to get into it tomm. I see the realys (the square boxes in the fuse panel?) I don't have one that says glow plugs. Any idea how this may be labeled?

[Kennedy]

The glow plug relay is actually a module. You won't get so lucky as to be able to pluck a simple plug in relay and swap it. DFollow the big cable to the top rear of the drivers side of the engine.

I guess the first thing I might do is probe the glow rail with a test light and key up cold to see if there is any power getting there. I'd really be surprised if it was anything other than this relay/controller.

[DmaxMaverick]

John's right, I was mistaken. There are no GP/heater relays in the power box. They're in the controller. Still, very easy to service. The controller is mounted above the rear driver side valve cover. If you are getting voltage to the GP's and heater during the key on cycle, check the heater and glow plugs as described before. If no voltage, the controller is likely bad. Easy to replace and not too expensive, unless you get it through a dealer. Your local parts store or Napa may have it. If not, go to online stores like www.gmpartsdirect.com or www.rockauto.com for the part. It'll be 1/2 the dealer cost.

Just to confirm....You have a federal emissions truck, don't you? If the glow plugs have individual wires powering them, it is a CA/NE emissions truck. If the plugs are powered by a single buss that goes from plug to plug, it's federal.

[Shed]

JK, DMAX thanks for all the info. I'm not sure if it is a federal or CA emissions truck. It was sold new here in Iowa, but I know that may not mean anything. Anyway to tell like the VIN? Sorry have'nt gotten back to you, working alot and no computer at home right now because of the remodel.

So just to recap, test the intake heater and the actual glow plugs. If no power to them, then it has to be the GP controller? And the controller will have to be replaced? Or just relays in the controller? Or are the relays and controller all one module? Is the GP controller a "plug-n-play" type of part? Just don't want to have to do any wiring or anything. Found a controller for $100, that sound in line?

Shed

[DmaxMaverick]

RPO code YF5 for CA emissions. NE1 for North East (same/similar as CA). FE9 for federal emissions. The RPO code can be found on the large sticker in the glove box. Yours should be federal, delivered to Iowa, unless it was dealer traded from another region.

The controller is "plug and play". Unplug, unbolt, replace, bolt, plug, done. The individual relays in the controller can be replaced, but they are each more expensive than the entire controller (going by dealer list). $100 for the complete controller (not just a relay) isn't bad. Rockauto has it listed for $96, and they usually have about the best price. Make sure you verify the part by your VIN, and get the correct emission region controller.

Correct. Checking power to the heater/plugs during a cold start cycle will tell you if the controller is sending power. If it isn't, it should be replaced. They are a more common failure item with your symptoms. To check the health of the plugs/heater, you'll have to disconnect the power lead to each, and check them for continuity/resistance. Not a bad idea to do now, since you are under the hood working on that system.

[Shed]

thanks maverick I will try to take care of it this weekend! I'll get back to you and let you know how it went!

Shed

[Shed]

Gentlemen, Out of curiosity I called my dealer to find out what they charge for a GP controller (federal emissions). To my suprise they have 3 and are going for 79$! How is this possible? They have raked me over the coals before but now they are beign reasonable???? I'm baffled! Think they are trying to suck me in and try to sell me something! Thought i would see what you guys thought of that price.
Shed

[DmaxMaverick]

That's probably for a single relay. If it is a genuine price for the entire controller, they made a mistake. The relays at the online stores are about $40 each, and the dealer MSRP is $79. Many times, they don't know what they are selling you, and good luck getting what you ask for. The repair procedure calls for relay replacement if a relay fails. We know better.

BTW....
Don't toss your old controller (it'll probably have at least one good relay and other parts). If you decide you just can't keep it, I'll pay S/H to take it off your hands......

[Shed]

I figured it was something along those lines. No way they are gonna be that nice to me! I'll just hope that I can pick one up at NAPA tommorrow. Just once I would like to feel like I'm gettin a few dollars back from the dealer! LOL. Oh well they have their job, I have mine! Thanks for everything, I'll let you know how it went.

[Kennedy]

This is one of those parts that I use genuine GM only.

[DmaxMaverick]

This is one of those parts that I use genuine GM only.

Normally, I would agree. However, this is a "dumb" component, unlike previous controllers. The activation and timing is determined by the PCM. The Duramax "controller" doesn't really control anything. It is only a common platform for relays. And, who's to say who manufactured the relays on the board? They could be the same (or better??) manufacturer, just in a different box, without the dealer markup. At the present time, we hear about failed GP controllers on occasion. I haven't heard of any of the aftermarkets failing, yet. They will, I'm sure, but we have nothing to show they will any more than the GM model. So far, only the GM's have failed, that I've heard of. Other, more critical components, I would agree 99%. Unless you are in the dead of a severe winter, this just isn't that big of a deal. That said, IIRC, gmpartsdirect's price is about the same as rockauto's aftermarket part.

[Kennedy]

Sensors, switches, relays, etc are seldom lower priced as aftermarket and almost never as good.