First problem I had was the check engine and check engine electronics came on but no glowplug light lit when key was turned on found one glowplug reading about 700 ohms replaced all glowplugs with bosch duraterm glowplugs. After replacing all glowplugs checked resistance at the relay and they are reading .6 ohms. Disconnected battery neg. to clear check engine light but it did not clear the display or check engine light. Went to autozone and checked the code and it is glowplug heater circuit. Also checked the voltage at the relay and all terminals were about 12.8 volts. Does anybody have any ideas to what the problem might be..

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84 300 Turbo / 320,000
96 E300 D / 55,000

Did they clear the code? If not, just drive normally for a few days and it will go away.

Note that starting the car before the plugs get up to temperature will also throw a glow plug code.

I think on this year car you can reset the codes by disconnecting the battery

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84 300 Turbo / 320,000
96 E300 D / 55,000

Do you no if the relay has a built in temp sensor or is it on the engine alot of the wiring isolation is coming off on different connectors on the engine. Do you have a wiring diagram for the glowplug circuit?

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84 300 Turbo / 320,000
96 E300 D / 55,000

PO380 occurs when start is attempted on cold GP's. Most commonly is user error, sometimes the relay. Will go out on its own if doesnt reoccur within 3 cold, hot, back to cold run cycles.

The wiring is part of the overall engine harness unfortunately. Is not sold separately.

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)

I checked the voltage with the glowplug connector off and the relay does not shut off the voltage is on all the time the relay does not time out do you have any ideas

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84 300 Turbo / 320,000
96 E300 D / 55,000

When you say "the relay does not time out", how long are you talking about?? On my vehicle, the glow plug light will come on, and go out after about 5-10 seconds. This does not mean that the relay has cut out. Depending on outside temperatures, my relay may stay engaged for up to 1-2 minutes. I have a Scanguage installed, and it gives me real time readings on about 13 different items. If I watch the voltage reading, it will normally stay at about 11.5-12 volts when the car is first started, until the glow plug relay cuts out, and then it bumps up to 13-13.6 volts. Hope this helps.....

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96 E300d

He's right, normally the GPs will "afterglow" for a couple of minutes and this is perfectly normal. It was done to help in emissions control when the engine is cold. If your GPs stay on for more than 2-3 minutes then I would check the relay out.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

All new glowplugs are working fine and the relay is working right I was checking the voltage with the glowplug connector off I guess the connector needs to be on for the the relay to work right. I thought on this year car you could reset the check engine light by taking the neg. side of the battery off for a few minutes but this did not work on the glowplug code problem but it did on another code problem I fixed a while back. Thanks for the help

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84 300 Turbo / 320,000
96 E300 D / 55,000

Disconnecting the battery doesn't reset anything on my '96.