Glow plug replacement questions

MITBeta

New member
2007 2500

My mechanic read this code: P0672 CYL 2 GLOW PLUG CIRCUIT

I replaced glow plug number 2 (middle cylinder, passenger side) and the glow plug light still comes on for the first minute or so after startup and the check engine light is still on.

What is the next recommended step? Replace the rest of the glow plugs?
 

gggGary

gggGary
The codes do not correctly indicate WHICH glow plug is out. Tell him to TEST for a defective glow plug. then if one is found, replace THAT plug(s).
 

MITBeta

New member
All the glow plugs were ohmed out through the harness that connects to the module and measured between 0.7 and 1.1 ohms. Does that suggest that it's a bad module?
 

Midwestdrifter

Engineer In Residence
All the glow plugs were ohmed out through the harness that connects to the module and measured between 0.7 and 1.1 ohms. Does that suggest that it's a bad module?
Yes, but with a caveat. Sometimes a glow plug will fail only when hot. Making a test harness with a 15A fuse to heat the plug before testing can be useful.

If you have the old style control unit I would replace it regardless. The new units do not have an internal fusible link, and do not require replacement when a glow plug shorts out.
 

MITBeta

New member
I replaced the module and on the next start the glow plug light went out with the rest of lights (didn't stay on for 3+ minutes as it had been doing).

The check engine light remained on for ~3 days, but this represented only a couple of starts from cold.

Thanks for the advice.
 

grozier

Member
Hi everyone,

I have the P0671 and P0380 codes on a 2004 NAFTA OM647. Checked the glow plugs with the 20A fuse method and all passed. I replaced the glow plug module (simple job once the headlamp is removed) and cleared the codes, but after the first cold start the MIL returned.

Any ideas on where to begin with the next level of diagnosis?

Many thanks,

Ted
 
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Goofy foot

sliding left...
grozier, Did your old module have burnt/broken thermal links? How old are the currently installed plugs? What is your mileage? When you look down into the plug wells (with a mirror) do you see signs of rust or black gunk? If you're in a cold weather climate which I assume Berlin is, you will want functioning glow plugs. Read other threads, and check wiring for resistances/continuity as well as the plugs for resistance. Also, did you remove and clean the grounding connection to the body below the module? It has a tendancy to get wet and corroded because of debris dumping through windshield gutter port.
 
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grozier

Member
Thanks folks for the replies. These are the original glow plugs with about 98k miles on them. MIL has been on since last winter (we only use the van for big trips) and starting in all weather (including freezing) is fine.

The resistance on all cylinders -- as measured through the harness -- was 1.0 - 1.2 Ohm. At 50F today, reading the OBD scanner, the pending DTCs would set every few seconds after starting. This must be during "after glow?"

I loosened the two ground connections just rear of the headlight, then re-tightened. Is there another ground out of sight below the module? I haven't dissected the old module, but it doesn't look physically damaged.

Maybe I should try a low amp fuse on each plug?

Ted
 

Andy at Focallocal

Social Adventurer
After an hour and the loss of much of the skin on my fingers trying to take the glow plug caps off by hand (I succeeded with 2) - I thought I'd post the tool mod I came up with for those who like me haven't got the correct tool.

These wire cutters made the job easy and I pulled the remaining 2. then put them back on to warm the engine up again. Then pulled all the caps off again in seconds.

You might not want to be reaching around grabbing things with limited vision inside your engine with a device designed to cut wires, so you'll note I wrapped the sharp ends in electrical tape to make them soft and friendly.

I hope this helps someone in the future
 

Attachments

I picked up a pair of glow plug pliers on eBay for 18.99 shipped. I got the angled ones but the straight ones might work better to be honest. I put some toyotalube in the holes and drive for about 2 weeks (130 miles) and then took it for a nice drive at lunch one day up and down the tollway then pulled into the shop and had them swapped before my lunch was over. It's really an easy job with the right tools. I had previously swapped the module with the newer design one but it didn't clear anything up. That job was more difficult than the glow plugs. The guy charging 800 in Chicago for swapping plugs is making a killing for 30 minutes of work!
 
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Jodean

New member
I had zero issues with my giant needle nose pliers, like $2 at harbor frieght, or might be part of a set, they really pull right off, pretty easy
 

Patrick of M

2005 T1N 2500 (NA spec)
I had zero issues with my giant needle nose pliers, like $2 at harbor frieght, or might be part of a set, they really pull right off, pretty easy
Unless they are stuck, then pulling on the cap pulls it apart, so you need to get under the capand push it up, hence the fancy pliers.
 
I am in the process of replacing the glow plugs in my 2008 as I write this. Five of six came out without issue. The middle one on the passenger side is stuck tight. I can only get a tiny bit of movement back and forth which is accompanied by the familiar sound of a seized fastener. I have already applied as much pressure as I feel is safe to apply. The engine is hot and I sprayed some blaster down into the seat of the plug.

Is this particular plug often stuck? Any tricks to share for its removal?

Thank you.
 

sikwan

06 T1N Can
I am in the process of replacing the glow plugs in my 2008 as I write this. Five of six came out without issue. The middle one on the passenger side is stuck tight. I can only get a tiny bit of movement back and forth which is accompanied by the familiar sound of a seized fastener. I have already applied as much pressure as I feel is safe to apply. The engine is hot and I sprayed some blaster down into the seat of the plug.

Is this particular plug often stuck? Any tricks to share for its removal?
This is the T1N section, btw. It sounds like what you're doing is good.

Did it soak overnight with penetrating oil? Now that you have it somewhat loose, I would let it soak some more, heat up the engine later, and try again.
 

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