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Glow Plug/heater Circuit A Malfunction- Po380

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Someone have an electrical wiring diagram of glowplugs circuit? I can't find it but it's could be helpful. :unsure:

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I hate to work on a car that I can't find any technical informations that I need to diagnose a problem.

So, that glow plug is really dead. But the other are still good.

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I test each connector to be sure there is a good contact between the glowplug and the connector.

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But there are always these lights on when I start the engine.

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So, I'll go back and disassemble for a 7th time today... :(

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i had the light on for #1 cyl being blown. once i replaced that 1 the light went out after a few cycles.

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That's what I though but yesterday I used to car in evening for some shopping and we cycle the ignition key almost 12 times during the evening but the light was still on when we were back home. It's begin to be annoying. I don't want to go to mercedes-benz dealer, they will break someting else as usual. I would like to inspect my wirring but without any wirring diagram, it's pretty annoying to find which wire is what and if it's normal that this one or an other are short to ground or not. So... my fingers are frozen and I'm tired to searching about I don't know what. I think that I will shut the trunk for today. It's enough.

Edited by dieselkiki

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I would just drive the car for a few days to see if it resets, if its not reset bt Saturday id looking into it then

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Must be glow plug season, my glow light stayed on this evening. This is a first!!! No CEL light tho' and yes I have the P0380 code on my OBD. I guess I will get 3 of those Japanese ones, and attempt to fit them. The car started OK, and I will try starting it in the morning. report back tomorrow.

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Yours is one of the highest km ones, I hope you keep her going for another long time!

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I would just drive the car for a few days to see if it resets, if its not reset bt Saturday id looking into it then

mine reset after about 2 days after I replaced one glow plug...

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Have you tried erasing DTC?As for wiring diagram, this is not really necessary for such a simple system. There is a single cable from each glow plug to the forward (square) glow plug controller connector. Positive feed in is also at the square connector plus smaller leads going to engine ECU. Cables from the rear (oval) glow plug connector go to the electric cabin heater elements.

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Thanks for tour advices guys.Tolsen: Yes, I tryed to erease dtc about 5 or 6 times but it reapear after the NeXT start. BUT, it's a very importants informations that you gave to me about both glow plug module connector. I didn't know that the ovale one drived the electric cabine heater. Could a cabine heater blown fuse or a defective heater core create this dtc? I get out of my bed and I go to see that.Tank you Tolsen. That's what I meaned when I wrote: I need to know what is what in this wiring. ;)

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Well, another wasted day to finding this glowplug problem. It's begin to make me crazy!! Since I'm back from the USA that I work on this annoying problem every day.

Today, I stip all the wiring above the glow plug (I removed the plastic sheild who keep the fuel lines). I test the continuity between glow plug controller connector and glow plug. Absolutely perfect.

I tested every fuses and I tested the electric heater core resistance (each 3 phase of the heater core) and it's good too.

I inspect each wire who reach the engine ECU from the harness above the glow plugs in the plastic sheild. I found "NO-THING". What the hell is turning the glow plug light and the cel "on". I don't know what to looking now.

But I found an interesting post on another smart forum that you wrote on Tolsen. The problem that this guy had and mine looks very similar. In addition, we both had to worked in the starter area... there is a link??

http://www.thesmartclub.com/board/showthre...ight-Staying-On

But even if I think about it from the early afternoon, I just can't understand what is the link between the starter and the P0380 dtc. Anyway... I'm really pissed off.

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I suggest you measure current from controller to each glow plug using a shunt and some custom made leads. Perhaps a plug got damaged during installation. Did you ream the bores?Can't see any possible link with starter. Too bad member DAVEX407 on theSmartClub never got back and reported any final conclusion.

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Yes it's sad when members don't report their conclusions! It's should be helpful! :( Glow plugs are all in good conditions. I removed it a lot of time since monday and every time I mesure the continuity and all are good. No reamer needed. The holes are cleans (I replaced the head last summer). So...

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Resistance of a glow plug may measure OK cold with a multimeter but the plug may fail when hot. The ultimate test is therefore to measure current or visually examine each plug glow. Beware you can damage glow plugs if you let them glow for more than a few seconds without any heat sink.

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Tomorrow I'll removed all glow plugs again and I'll plug it direct on a 12v. battery charger. But I guess they will be all bright hot! I'll let you know. But seriously, this is the most annoying trouble I had with this car exept for my valve train problem of last summer.

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If the glow plugs all work then you have a sensing circuit problem. Look at the wires that feed back to the ECU the current draw of the glow plugs. I don't know, but I would expect that the glow plug controller (that you replaced) measures the current, then sends a signal to the ECU. Is it an on/off signal, or a level corresponding to the current draw, or is it coded data? No idea, but the ECU thinks there is a problem when none exists.

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That is the problem now. No one have any information about the wiring of this box and on how this controller work. If I know which wire do what, it could be easiest to diagnose and inspect the right wire between controller and ecu. Some of you get the "wis" shop manual? Maybe that this precious information could be on it...

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That is the problem now. No one have any information about the wiring of this box and on how this controller work. If I know which wire do what, it could be easiest to diagnose and inspect the right wire between controller and ecu. Some of you get the "wis" shop manual? Maybe that this precious information could be on it...

I'm still learning how to use my MBStar package...here are some info that I was able to pull off WIS, hope they'll help you.Wiring_diagram_for_electronic_diesel_transmission_control__EDG_.pdfComponent_description_for_the_glow_output_stage.pdfCDI_starting__function.pdfComponent_description_for_glow_plugs.pdfGood luck, I'll try to find some more this weekend if this stuff helpsIzzy Edited by stickman007

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Thanks Izzy! ;) I really hope to find one of these MB start multiplexer soon!! It's so much the right tool to work on smart and mercedes-benz products when you have an electonic issue.

So, I finaly found my problem source. I can resume in a single sentence: When you try to diagnose a glow plug problem, be sure that your multimeter battery are in good condition and that this one showing the right data!! :whistle:

So, I removed all glow plugs and I put 12V on each with my 12V battery charger. Cyl. #1 glow plug didn't glow even if my multimeter indicate inner continuity. I replaced the 9V multimiter battery and after it read an open circuit on the same glow plug.

Almost a week wasted and freezing fingers because of a bad multimeter!! It's a bit frustrating.

I'm sorry about all that time I maybe make you wasted about this problem but still thanks to Tolsen and all other for your advices. That was appreciated!

It's still on of the many tight places to work on smart.

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Edited by dieselkiki

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I'm still learning how to use my MBStar package...here are some info that I was able to pull off WIS, hope they'll help you.Good luck, I'll try to find some more this weekend if this stuff helpsIzzy

Thanks Izzy but those are for the 451. Very valuable info anyway and not too different I hope.

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Thanks Izzy but those are for the 451. Very valuable info anyway and not too different I hope.

Thanks for the clarification Tolsen,Its one of the most confusing programs I've ever used! Takes forever just to find out simple information on WIS, (maybe I just suck at this). On another note, is the diesel 451 engine/electronics almost identical to the 450? I've read somewhere that it uses essentially the same engine.Izzy

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It's almost the same engine but there is some little difference like EGR valve, oil filter housing, injectors, fuel pump, fuel temp. sensor, glow plug controller look different too, o2 sensor and other little things.But overall, it's the same engine.

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I had a good look at a 451 CDI when we were in Spain last year. It looks very different in the engine compartment, but that's mostly the peripherals. The engine itself is supposed to be almost identical. It looks like everything other than the engine is new, intercooler, EGR, hose and wire routing, I think even the fuel rail, everything looks different, so I would be very surprised if the ECU is not changed substantially as well. Also the tranny is new, 5 speed now.

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