Glow plug circuit open P0671 running out of ideas :-(

LeisureSprinter

New member
hi, I'm having
P0671 Cylinder 1 glow plug circuit open and
P0380 Glow plug heater circuit A

Clearing them many times, they come back.

I have measured cable resistance between controller and plug 0.9 ohm, cable seems good

Replaced the controller - no change

Measured plug to block 1.4 ohm, replaced the glow plug anyway, installed new Bosch plug, also 1.4 ohm (after the new plug the errors disappeared for a few starts and came back)

So with a cable which appears to be good, and replacing the controller and glow plug making no difference, what else could be wrong?

thanks!!!
 

Brokecanadian

2005 Cargo 2500 SHC NA
Do you have an original controller?

The old glow plug modules blow permanently for each fuse

Sent from my SM-A705W using Tapatalk
 

BrennWagon

He’s just this guy, you know?
This may be a symptom of a ground strap that’s starting to fail. The glow plug circuit has a pretty heavy current draw and when my engine to chassis strap went the codes for the glow plug circuit were among the major error codes that scanned at the time. Do you get any other codes that point to low voltage or low pressure in other systems?
 

220629

Well-known member
If you didn't buy a newer model self reset GP controller, as suggested an existing problem could take out a fuse.

Have you checked all of the glow plugs? There have been reports that the DTC's are not always accurate as to a specific cylinder being the problem.

My preference is the Doktor A fused test lead vs using an ohmmeter to check glow plug condition. I use a 25 or 30 amp fuse for the test lead. A bad/shorted glow plug will blow a 25 or 30 amp fuse if the probe is held too long. For a bad/shorted GP, using a 25 - 30 amp fuse vs a 20 amp gives you a split second longer to notice the heavy spark when touched and allows removal of the test probe before the fuse blows. A good GP sparks a bit when touched with the probe, but it doesn't "snap" for lack of better description. Once you know the "normal" spark it's easy to tell the difference.

:cheers: vic
 
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LeisureSprinter

New member
I believe I have a newer no-fuse controller and I've bought a brand new controller as well, so I would doubt it's a fuse. Also the problem is sometimes intermittent, like I've started and driven the car a few times before it came back. I've guessing a blown fuse would always cause errors consistently?

Can the "circuit open" error be given when the circuit is actually shorted not open? That's why I have not done the Doctor A test yet, specially after trying both the old and a new glow plug. But I will likely try it as I'm running out of other ideas.

To test for a wrong plug number reporting I've disconnected the first plug wire and started the engine a few times - I've been getting exactly the same errors pointing to #1, so I'm guessing the reporting is correct.

I'm not getting any other errors or any other malfunctions.

I'm going to check the grounding as well. Thanks for the responses so far...
 

Cheyenne

UK 2004 T1N 313CDi
Have you checked all of the glow plugs? There have been reports that the DTC's are not always accurate as to a specific cylinder being the problem.

:cheers: vic
Somebody posted a wiring diagram recently that showed Glow Plug 1 as being cylinder 5, GP 2 as Cyl 4, GP 3 as Cyl 3, GP 4 as Cyl 2 and GP 5 as Cyl 1.

Suggest you follow Vik's advcie and test each and every GP with a fused wire.

Keith.
 

Brokecanadian

2005 Cargo 2500 SHC NA
If you run out of ideas after all these tests, you might try testing all wires involved while moving the harness, looking for an intermittent faulty wire

I replaced my entire engine harness after finding a faulty injector wire by accident. Wire was broken inside the insulation, but by pushing on it, the connection was made and engine smoothed out. By the time I found it, I was getting codes for 3 injectors (and about 40 others) I chose to buy a new harness, because I use van for work and other wires probably weren't far behind.

It's the glowplugs so DON'T buy a new harness. DO wiggle the wires with a multimeter attached, if nothing else proves to be a solution. Wires can look fine but break inside the insulation

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LeisureSprinter

New member
Ground is very solid (it's a southern rust free van never in salt/snow) but I've also sprayed ground and battery connectors with DeoxIT to soak them for cleaning and will see...

Another thought - strapping a spare good glow plug with visegrips to the block/good ground, connecting with the same connectors and seeing if it heats up ok and/or throws an error - has anyone tried that or has any comments about such apprach?
 

Brokecanadian

2005 Cargo 2500 SHC NA
Besides the obvious safety concerns:). That would definitely show you if it worked or not. Make sure it can't fall on anything important if it moves when heated up

Let us know :)

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Midwestdrifter

Engineer In Residence
Sometimes a glow plug only fails open when hot. The fuse method is one way to check. Another is a clamp on ohm-meter. Clamp on to each wire (with 10 minutes cooldown in between). Cycle the ignition on. The plug should pull 20A or so for a few seconds, then taper down to ~5A. If it drops right off, you may have a failed plug.

The code itself won't cause issues, assuming you are not having trouble starting.
 
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220629

Well-known member
...

The code itself won't cause issues, assuming you are not having trouble starting.
:thumbup:

Unless there is an emissions test in the future. Depending upon the jurisdiction, some states/areas require the MIL aka CEL to be off with no emissions related DTC's.

:cheers: vic
 

LeisureSprinter

New member
Well guys you are right about doing the fuse test regardless of what the error codes say. I've tested all the 5 circuits in many ways, consistently glow plug #2 blows the (25A) fuse 3 times, no other plugs do that, no shorts to ground or to other wires found in the wiring.

So in summary the message "Cylinder 1 glow plug circuit open" means "Cylinder 2 glow plug circuit shorted to the ground" . So time to replace plug #2 and we will see how it goes after that.

Thanks!!!!
 

Nautamaran

2004 140” HRC 2500 (Crewed)
Somebody posted a wiring diagram recently that showed Glow Plug 1 as being cylinder 5, GP 2 as Cyl 4, GP 3 as Cyl 3, GP 4 as Cyl 2 and GP 5 as Cyl 1
I’ve never physically traced them, but the diagram shows the module connector’s pins 5..1 feeding cylinders 1..5 (pin 6 is not connected).
So if the module reports its faults by pin then the codes will point at the wrong plug...
(in my case I had a few bad plugs, so skipped further diagnosis and simply replaced all five, and repaired three blown fuse links within the original module)

-dave
 

Nautamaran

2004 140” HRC 2500 (Crewed)
Well guys you are right about doing the fuse test regardless of what the error codes say. I've tested all the 5 circuits in many ways, consistently glow plug #2 blows the (25A) fuse 3 times, no other plugs do that, no shorts to ground or to other wires found in the wiring.

So in summary the message "Cylinder 1 glow plug circuit open" means "Cylinder 2 glow plug circuit shorted to the ground" . So time to replace plug #2 and we will see how it goes after that.

Thanks!!!!
Hmmm... browsing “The Complete Fault Code Guide”, they only list one glow plug fault for the CDI3 (engine) module:
1482-1 pre-glow “at least one gp has a short circuit”

http://diysprinter.co.uk/reference/T1N_CompleteSprinterFaultCodeGuide.pdf

I’ve noticed that the CDI3 module seems to map its (usually very detailed) internal fault codes (as returned by the Sprinter-specific Module/Read Codes menu path) onto the EPA-mandated OBDII faults (accessed by generic scanners, or by using the OBDII menu on even the best scanners)
The generic faults are usually less specific, but in this instance it would seem that MB chose P0671 / P0380 as a stand-in to satisfy the EPA, even though it is more specific?

It would explain why even Dr. A continues to recommend the “fuse test” to diagnose failed plugs, rather than simply trusting the fault code generated.

-dave :2cents:
 
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rv-sprinter

07 Winn View 23J - 06 T1N (NAFTA)
Well guys you are right about doing the fuse test regardless of what the error codes say. I've tested all the 5 circuits in many ways, consistently glow plug #2 blows the (25A) fuse 3 times, no other plugs do that, no shorts to ground or to other wires found in the wiring.

So in summary the message "Cylinder 1 glow plug circuit open" means "Cylinder 2 glow plug circuit shorted to the ground" . So time to replace plug #2 and we will see how it goes after that.

Thanks!!!!
LeisureSprinter,

Did plug #2 replacement correct the error codes or was it something else?
I have the same error codes that you had.

And is that #2 from the front of the engine?

Thanks :popcorn:
 
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jrod5150

Well-known member
I’ve dealt with this issue of incorrect glow plug mapping before. I Like to change them all which eliminates the issue. Of course that can open a can of worms with a set that hasn’t been changed in a long time or from a corrosive environment. Btw if your using an eBay Chinese new $35 controller might as well throw it in the trash they are complete garbage.
 

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