Hi - These 2 warning lights came on today on my '99 E300 Turbo with 192,000 miles on it. I've searched here and found related links that suggest it is the glow plugs causing at least one of the warning lights. Maybe a MAF problem causing the other light but my question is is it OK to drive like that or does it cause damage to anything? Do the Glow Plugs only operate pre-ignition or is there always juice to them even when driving?

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

How is it running after up to temp? If it is running normally then you can drive it. A glow plug going bad makes the gp light stay on along with putting the check engine light on. Resolve the glow plug issue first.

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Jim

The GP light also stays lit when the engine is started without waiting for the GP's to first get hot; it registers as cold (ie dead) GP's and sets the GP light. Will reset itself after 3 cold/hot run cycles if that is what happened.

Pull the codes and find out what the problem is; thats the easiest solution.

If you have a bad GP you'll need to test the resistance at the GP relay to determine which one is bad.

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Terry Allison
N. Calif. & Boca Chica, Panama

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

Easy, quick test is to disconnect the wiring going from the glow plug relay to the glow plugs and check resistance to ground on each pin. The last one I had in here with the issue was reading over 200 ohms on the bad glow plug. All the others had readings under 2 ohms. This is kinda a quick/easy test.

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Jim

Thanks guys! The car runs fine -I was afraid it would drop into 'limp home' mode on me yesterday but it was running strong. I will check the ohm readings out this weekend.

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dtf
1994 E320 Wagon (Died @ 308,669 miles)
1995 E300 Diesel (228,000)
1999 E300 Turbodiesel ( died @ 255,000)
2006 Toyota Tundra SR5 AC 4X4 (115,000 miles) rusted frame - sold to chop shop
2011 Audi A4 Avant (165,000 miles) Seized engine - donated to Salvation Army
BMW 330 xi 6 speed manual (175,034 miles)
2014 E350 4Matic Wagon 128,000 miles
2018 Dodge Ram 21,000 miles

In all likelyhood it is just a bad gp.

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Jim

Agreed - that's what happened on mine.

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Len
'59 220S Cabriolet-SOLD and living happily in Malta
'83 240D 351,500 miles original owner-SOLD
'88 560SL 41,000 miles - totaled and parted out
https://sites.google.com/site/mercedesstuff/home
'99 E300 turbo 227,500 miles
'03 SLK320 40,000 miles - gave to my daughter
'14 Smart electric coupe 28,500 miles
'14 Smart electric cabriolet 28,500 miles
'15 Smart electric coupe 28,000 miles

Same here as well. Once GPs were replaced, CEL went off.

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2013 Volkswagen Jetta Hybrid SEL Premium (Sparky)
http://badges.fuelly.com/images/smallsig-us/193500.png

It's a car not a science experiment! Open the throttle!