Help me fix P0380 before the goverment takes my car away

I need new stickers and can't get them with the CEL on. I have an intermittent P0380.

1999 Beetle ALH 5 speed

So far I've done the following:
Confirmed power at the harness (it's only 9v with the glowplugs hooked up)
Confirmed all plugs are 0.6 ohms cold
Soldered the 2 glow plug wires together
Cleared the code
Considered moving to an area with no e-testing

I was pretty sure soldering the 2 wires together would solve my issue but it didn't. I'm suspecting it's because I'm only getting 9v at the harness (that's with the glow plugs hooked up though). I did go in VCDS and increased my glowplug duration back at the beginning of winter, I think I'm going to try lowering that as much as possible to see if it helps.

What should I look at next? My sticker is already expired so I'm on borrowed time. Worst part is I have a trip to the USA coming up in 2 weeks and I'd rather not cross the border with expired stickers.

An intermitant p0380 is almost always a poor connection between the harness and the glow plugs.
These harnesses do fail over time.
The proper remedy is to replace the harness.
Sometimes carefully wrapping a tiny piece of aluminum foil over just the contact pin on the glow plug and re-installing the harness will make a better connection.
BTW....A simple way to test ALH glow plugs is to use a test light....clip the aligator clip on the positive battery terminal and touch the probe to the top of each glowplug contact....if the plug is good the light will light up, since there is continuity to ground.

Doesn't splicing the 2 wires together trick the ECU into thinking everything is fine even if there is a poor connection?

burn.. does it come back right away? you're allowed not ready monitor. If you reset the codes, drive around until all but one is not ready and take it in youll be good. Its not a solution but it will get you your stickers. Also, you can pay for a diagnostic fee from a shop and hope their quote comes in more than $450 and they will give you a conditional for two more years

I hate e-testing but with the new odb only scanning you can almost manipulate the test easier than the tail pipe testing.

I didn't know that we are allowed 1 not ready. I got 2 days from clearing the code to the light coming on again so I'd have to time it perfectly assuming that the other monitors were all ready.

I've never had to do an e-test before. I'm aware of the $450 bribe but I'd rather not dump that much money into the car.

If you get 2 days then you have an intermittent and it's probably in the harness itself. I had something similar happen with my '03 (different setup on the glowplug harness as it checks each plug individually) where I could clear the code and clean up the plug ends with a small wire brush but it would still come back in a few days. The only way I was able to stop it for good was to replace the harness itself.

I could have spliced wire and ring terminals into the wiring along the way but given how much of a pain it is to un-loom that thing I found it MUCH easier to buy a replacement harness, plug the new one in at the plenum connector and use some cable flex to route it along the existing harness loom, zip-tied into place. It's been trouble-free since other than two actual burnt-out GPs that I've had to replace in the last few years.

Check fuses on top of battery - one of them is for the glow plug harness. See if there's any corrosion on them (pull them and check). Also if it's the same as a 200 Jetta, relay #180 under the dash powers the circuit. I'd inspect that too for any corrosion. You can bench test it for consistent operation/connection.

If all that looks good, it's either harness or glow plugs. You can pull the plugs and measure the resistance for each of them and see if any are of out of spec. Also look inside the harness connections for corrosion there too.

If none of that addresses the issue, then I'd consider a new harness.

Regarding the fuses on the top of the battery, is it one of the flat ones held in with the 10mm nuts or one of the 3 green fuses (30 amps I think?). I did inspect all those fuses and the green blade style ones are awful and will be replaced ASAP but the flat ones were all perfect.

I'll try threading the glowplugs and installing nuts and ring crimp things like Vince Waldon suggested in one of the threads I read. I have a hard time paying $100 for a part that's going to fail again

it's one of the ones that is bolted down. second in from the right (when facing them).

As for the harness, all parts can fail with time. My harness is 17+ years old and still works fine. So I don't know if one is "going to fail again" for you in the reasonable time you'll likely own the vehicle.

Well that makes it a bit more worthwhile then. The way I was reading it, it seemed like a semi-annual thing to replace. Thanks.

burn_your_money said:

Well that makes it a bit more worthwhile then. The way I was reading it, it seemed like a semi-annual thing to replace. Thanks.

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Yours is presumably 19 years old. You could get 20 out of the next harness...

No, mine's already been replaced at least once by the previous owner. I think I'll remove, test and thread them. It doesn't seem too bad of a job to do.

I replaced mine once at ~5-6 years of age on the vehicle, and the replacement has been fine with no problems since.

burn_your_money said:

I'll try threading the glowplugs and installing nuts and ring crimp things like Vince Waldon suggested in one of the threads I read. I have a hard time paying $100 for a part that's going to fail again

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?????
I'm sorry but that's plain silly.
Do you put tires,brakes etc,etc on your vehicle occasionally?
The glow plugs are designed to help your tdi start not just to pass an emisions test....why wouldn't you want a functioning glow plug system?????

maxmoo said:

?????
I'm sorry but that's plain silly.
Do you put tires,brakes etc,etc on your vehicle occasionally?
The glow plugs are designed to help your tdi start not just to pass an emisions test....why wouldn't you want a functioning glow plug system?????

Click to expand...

He's talking about making a bolt on harness not eliminating the glow plugs

maxmoo said:

?????
I'm sorry but that's plain silly.
Do you put tires,brakes etc,etc on your vehicle occasionally?
The glow plugs are designed to help your tdi start not just to pass an emisions test....why wouldn't you want a functioning glow plug system?????

Click to expand...

What I'm saying is an electrical harness shouldn't be a wear item. It's a poor design if it is. Also, why spend $100 when I can spend way under $20 and come up with a significantly better harness.

You might get lucky applying some dielectric grease to the glow plugs where they interface with the harness. Even if it doesn't fix the problem, consider it with a new harness.

I like the idea of rebuilding that GP harness. They sell the bits like the boots etc.

You can also have high resistance/poor connections through the glow plug relay. Or inside the relay itself.

You have to do a voltage drop test from inside the car to the plug connection on the engine, while some sort of load is placed on the system.

When you say plug connection do you mean the glow plug harness?

Yes, the four connectors made into the "bridge" otherwise known as a harness.

The glow system in these cars is brutally simple, not much to it. I have had DIYrs come in here having given up trying to fix them, only to find out their cheapo Chinavolt multimeter was unable to properly check the plugs. Have had that happen a couple times. My Fluke ET88 works fine. It also cost $400. 25 years ago. Used ones are still worth north of $150. You get what you pay for sometimes.

2 cents of input - I used to have these codes each season-change, then I put some dielectric grease into each GP socket and they have been error free for several years now. Cheap insurance...

paul_cat said:

2 cents of input - I used to have these codes each season-change, then I put some dielectric grease into each GP socket and they have been error free for several years now. Cheap insurance...

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Same.

My harness is past the point of grease. If I go with a factory one I'll definitely grease it.

Does anyone have a wiring diagram for the glow plug circuit? I'm having a hard time understanding how the ECM monitors the glow plugs if there is only 1 relay.

oilhammer said:

My Fluke ET88 works fine. It also cost $400. 25 years ago. Used ones are still worth north of $150. You get what you pay for sometimes.

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I'm still using my Fluke 77 vintage late 70's (iIrc)
Doesn't have the newer features and I could use a max/min & freeze.
Maybe scope in one also.

i've repaired several composite glow plug harnesses by breaking off the over molded rubber, tightening the female bullet connectors, reinserting them into the plastic sleeves, and heat shrinking the bare crimps... I squeeze a little bit of black silicone into the top end of the plastic sleeves around the wire to hold it in place

Well I made some time after work this morning and threaded the glowplug terminals and built a simple harness. I'm back to having 2 wires instead of just one feeding the glowplugs. I cleared the code and shall see how long this lasts. Considering how quick and easy it was I'm surprised that anyone bothers with the factory style harness.

I tested the glowplugs while they were out and they all started smoking almost immediately when put to power.

Regarding cheap testers, I used my cheap one at home and my not so cheap one at work. Both gave similar numbers so I don't think that is my issue.

burn_your_money said:

Well I made some time after work this morning and threaded the glowplug terminals and built a simple harness. I'm back to having 2 wires instead of just one feeding the glowplugs. I cleared the code and shall see how long this lasts. Considering how quick and easy it was I'm surprised that anyone bothers with the factory style harness.

I tested the glowplugs while they were out and they all started smoking almost immediately when put to power.

Regarding cheap testers, I used my cheap one at home and my not so cheap one at work. Both gave similar numbers so I don't think that is my issue.

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Post a pic. Would like to see your setup

I got my bill for the parts. I buy through work so I get it at cost plus I had some parts already. Grand total $0.40. I used 40 inches of 14 gauge wire, 4 ring terminals, 8 #10-24 nuts, 2 quick crimp connectors and some glue filled shrink wrapping. I would have preferred to solder the wires to the harness but the factory wires were too short so I made due.

I'm also happy to report that I passed the e-test and should be getting my sticker tomorrow.

I'll post pictures soon.

Now that sounds like a pretty solid fix/upgrade.
Always better to crimp than solder, too.