E300 96 Glowplug malfunction - PeachParts Mercedes-Benz Forum

radunegru · #1 06-14-2007, 09:49 PM

I do have those codes
P0120 Throttle/Pedal Position Sensor/Switch A Circuit Malfunction
P0380 Glow Plug/Heater Circuit "A" Malfunction
What should I check first?
forgot to mention that all glow plugs are new and the relay also.
Changed by the dealer 5k miles ago

e300D97 · #2 06-14-2007, 10:37 PM

It could be a failing battery. If the battery voltage gets too low its known to throw a bunch of codes.. I would have the battery tested and if the voltage is low try a long slow charge.

TMAllison · #3 06-14-2007, 10:47 PM

Are you experiencing a no start condition?

PO380 can be tripped by attempting to start on cold GP's which oftentimes occurs if key is turned numerous times in secession trying to start with another fault condition present. Computer eventually notes cold GP's so trips circuit A malfunction.

PO380 will clear itself after 3 successful start/run cycles (1 cycle = running up to operating temp and then cooling down) which typically takes 1-1/2 days if car is a daily driver.

If you believe this may have occurred I'd look at the other fault first.

I don't have any experience with PO120 so dont know how to advise you conerning it. The throttle is electronic, the sensor could be bad?

*edit*
e300D97's post is very plausible.....wasnt there when I began typing (phone rang). I'd follow his suggestion first.

dukegrad98 · #4 06-14-2007, 10:51 PM

Mine's throwing a P0380 as well. I think it's the #2 glowplug. I'm scared to change it, after hearing horror stories about them breaking and having to send the head off to a machine shop and so on. The prior owner changed the relay on mine, so I know that's not it. Got a full set of plugs in the trunk, but not the courage to open things up and change them out!

Cheers, John

aklim · #5 06-14-2007, 11:22 PM

You won't know which one is stuck till you try to take them all out. As I have always said, what may not be stuck today might be stuck next month.

radunegru · #6 06-15-2007, 12:16 AM

""It could be a failing battery.""
The battery is 4 months old.
Now let me tell you more details:
1 when I am turning the key the light on glow plug does not light up. I am starting the engine after 30 sec.After the engine starts the glow pug LIGHT COMES ON. After few minutes it goes away.

radunegru · #7 06-15-2007, 06:17 AM

I was trying to reset the check engine light but no luck. The check engine light comes back on on the next engine start.

e300D97 · #8 06-15-2007, 08:08 AM

Did you do the glow plugs yourself? I hate to see the glass half empty, but maybe whomever did them if it wasnt you didnt replace all of them. If they found one stuck they might have just ignored it. If you are sure they all have been replaced, it could be as simple as one of the connectors fell off, or there is a broken wire somewhere.

nhdoc · #9 06-15-2007, 12:15 PM

Start at the basics and forget that the plugs were recently changed...that doesn't mean one isn't bad which is what it sounds like is wrong. Test the GPs with an ohm meter and see what they read in resistance. You can do it from the relay plug and there are many posts elsewhere on this forum disucssing how...then you will know if it is GP or the relay that is bad.

How does it run after a cold start? Is there roughness for a while, like one cylinder is misfiring? That would also point to a bad GP. Also, not reaming out the holes can lead to premature failure I have heard. Do you know if they cleaned out the holes?

Finally, if the work was done at a MB dealer 5 months ago I'd take it right back to them. Parts are guaranteed for 12 months and their labor ought to be redone as goodwill if you now have problems with either the GPs or relay.

jimelde · #10 06-15-2007, 12:20 PM

if your glow plug light dosen,t come on with the ign. your glow plugs are bad . replaceing the glow plugs cured my 96 e300 with 176000 miles

radunegru · #11 06-15-2007, 08:27 PM

I did have the original receipt from MB dealer that the glow plugs were changed.
What's the life span of the glow plugs?

aklim · #12 06-15-2007, 09:52 PM

Quote:

Originally Posted by jimelde

if your glow plug light dosen,t come on with the ign. your glow plugs are bad . replaceing the glow plugs cured my 96 e300 with 176000 miles

When mine went bad, the light did the pre-glow thing and after start, they came on and stayed on.

aklim · #13 06-15-2007, 09:53 PM

Quote:

Originally Posted by radunegru

I did have the original receipt from MB dealer that the glow plugs were changed.
What's the life span of the glow plugs?

Same as a light bulb. Hard to really say. Problem is that because of emissions, you turn it on and off with every start. However, 5 months is kinda low. In any case, do the ohm test and let us know what you see.

nhdoc · #14 06-16-2007, 06:26 AM

Like AKLIM said, the life of a GP depends on how many starts you make on it, how many cold starts and how cold it is where you live, but I would say under "normal" circumstances you'd be looking at 4-5 years or about 50K miles between changes on these cars as a minimum.

I changed all of mine in 01/05 when I bought mine and that was almost 35K miles ago and no troubles yet. I suspect they were the originals from 1998 with 115K miles on them but mine was a southern car and the GPs don't get as much time on in warmer weather as they do in colder climates so they tend to last longer down there.

radunegru · #15 06-18-2007, 06:34 PM

I did a long trip about 600miles over the weekend on a hilly road pushing the car to the limit. After 300miles the check engine light went away. I am curios to start it cold tomorrow to see if it will come back again.
Any comments to this?