Glow plug light but no diagnostic code

[e280x]

So I've had this problem for a while on the E280 CDI OM642
When turning the ignition on the Glow plug light comes on for a few seconds and then goes out as normal.

The car starts first time after the engine turns a few times.

After around 20 seconds the glow plug light comes on again and stays on for exactly 1 minute.

This only happens when the car is cold. When warmed up there is no glow plug light on start up.

I used a standard OBDII module to read the codes and it didn’t show any.

I was then advised on this forum to purchase a more specialised icarsoft reader and bought the new MB V2.0 model.

Found some stored historic codes but still none relating to the light.
Any ideas?

Should I just go medieval and start testing each part with a millimetre and see what I can find?

Saw a set of 6 Bosch Duraterm plugs on ebay for £44, At this price it may be worth just changing them all. Any one used this particular model plug before?
6x Bosch Glow Plugs for MERCEDES CLS 3.0 CLS320 CLS350 CDI OM642 NO SCR | eBay

 

[DSM10000]

It might be the control unit. Star will be able to diagnose where the problem lies.

 

[e280x]

Yea that’s a possibility too but I would have thought the icarsoft reader would pick up on something like that and provide an error code?

 

[BlackC55]

A Star will pick up all the codes other readers wont. Its often a false economy to use generic readers as they don't give all the information. Remember codes are just a guide.

 

[HITECH]

This year quite a few cars Ive done had glow plug module error codes with glow plug light coming on and off. Ive changed both the module and glow plugs on some and the same fault persists with the same error codes even tho the control module and glow plugs are working normally. (both checked for voltages and correct timing). I have even stripped down some modules and checked components and the obvious thermal fuses. All these customers went away happy enough knowing as long as they are working fine then no biggie. I also done continuity tests on the loom ruling out any open circuits, earth's and short circuits. A few people who have gone to mercedes dealerships said they did get rid of it by getting them to re-flash the ECU. They will say its been upgraded but in actual fact it is a default map that is loaded into the car by the car's VIN number.

 

[PXW]

ISTR that this was effectively a notification of which glow plug needs replacing - the intervals between the light going off on startup and coming on again/how long it stays on tells you which plug is failing. Had it on my old 280CDi and just whipped it in to Olly to change the glowplugs - problem solved.

 

[HITECH]

Unfortunately thats not the case with a lot of them including my own W03. Changing ALL the glow plugs & Module makes no difference. Quick trip to the dealer for a 15 minute plugin session and most get sorted.

ISTR that this was effectively a notification of which glow plug needs replacing - the intervals between the light going off on startup and coming on again/how long it stays on tells you which plug is failing. Had it on my old 280CDi and just whipped it in to Olly to change the glowplugs - problem solved.

 

[PXW]

I’m sure you are right since you see a lot of these. I only mentioned it because that was the answer on my car which was the same model as the OP

 

[OneForTheRoad]

This year quite a few cars Ive done had glow plug module error codes with glow plug light coming on and off. Ive changed both the module and glow plugs on some and the same fault persists with the same error codes even tho the control module and glow plugs are working normally. (both checked for voltages and correct timing). I have even stripped down some modules and checked components and the obvious thermal fuses. All these customers went away happy enough knowing as long as they are working fine then no biggie. I also done continuity tests on the loom ruling out any open circuits, earth's and short circuits. A few people who have gone to mercedes dealerships said they did get rid of it by getting them to re-flash the ECU. They will say its been upgraded but in actual fact it is a default map that is loaded into the car by the car's VIN number.

i have to agree with this, i changed all 6 plugs and a new module , and still get white smoke if i just crank from cold. if i give 2 or 3 heats its all good .

 

[HITECH]

Yeah wasnt meanin to sound like an a**hole bud. I wish they all worked properly like they should do when u replace the parts. Its a weird one why the part of the map that does the glow plugs goes corrupt. Then re-flashed it fine. Glad urs was fine bud !

I’m sure you are right since you see a lot of these. I only mentioned it because that was the answer on my car which was the same model as the OP

 

[Old spanners]

So I've had this problem for a while on the E280 CDI OM642
When turning the ignition on the Glow plug light comes on for a few seconds and then goes out as normal.

The car starts first time after the engine turns a few times.

After around 20 seconds the glow plug light comes on again and stays on for exactly 1 minute.

This only happens when the car is cold. When warmed up there is no glow plug light on start up.

I used a standard OBDII module to read the codes and it didn’t show any.

I was then advised on this forum to purchase a more specialised icarsoft reader and bought the new MB V2.0 model.

Found some stored historic codes but still none relating to the light.
Any ideas?

Have a look at this YOUTUBE for a Jeep Grand Cherokee same OM 642 engine should help you out as it's very comprehensive,

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Should I just go medieval and start testing each part with a millimetre and see what I can find?

Saw a set of 6 Bosch Duraterm plugs on ebay for £44, At this price it may be worth just changing them all. Any one used this particular model plug before?
6x Bosch Glow Plugs for MERCEDES CLS 3.0 CLS320 CLS350 CDI OM642 NO SCR | eBay

 

[e280x]

So finally got a chance to take out the Glow plug relay and check each plug from the wiring connector based on the video posted above - Thanks to "Old Spanners"

If any one else with the same problem comes across this post and doesn't have the time to watch through the whole video I have attached some of the main screen shots to this post. It would be worth having these with you when carrying out the diagnostics.

For my issue it turns out the plug in the far right corner of the engine is giving a high reading.

So one questions I have... How do you get to the plug (P0676) located under the black cable tray circled blue in the image below. This cable management part goes under the turbo pipe / fuel filter and comes out the other side of the engine.
Has any one seen a full video of the plugs being replaced on this engine set up?



Would be good to hear from some one that has carried out this work them self as I will need to get this plug out quickly before the engine cools down.

 

[SL300-24]

You can get to this glow plug without moving anything I believe, long glow plug socket set 8mm.
Check the torque for undoing and tightening because they can snap off.

 

[Greek God]

Firstly thanks for all your information, but may I ask for some further help.
I have had the same symptoms and changed the control unit and all glowpugs with MB supplied items.
My glowplug light still stays illuminated permanently from ignition on and the plugs do not appear to prewarm as the car seems to need more
Churning to start especially if left for a few days.
Just had a service by indy who tells me the glowplug module has a lin bus link to the alternator which is probably at fault.
Does anyone else have any ideas? Or is it a new aleternator!

 

[HITECH]

Thats an interesting one because various ones I worked on had Battery Charge faults - Visit workshop dash alerts on them. Something I will probably look into a bit more now... Sorry I cant give any help concerning it right now.

Firstly thanks for all your information, but may I ask for some further help.
I have had the same symptoms and changed the control unit and all glowpugs with MB supplied items.
My glowplug light still stays illuminated permanently from ignition on and the plugs do not appear to prewarm as the car seems to need more
Churning to start especially if left for a few days.
Just had a service by indy who tells me the glowplug module has a lin bus link to the alternator which is probably at fault.
Does anyone else have any ideas? Or is it a new aleternator!

 

[OneForTheRoad]

Try 2 heat cycles and see if things improve. I read it can also be low fuel pressure related. Bit of a bug bear for the om642 is the heat plugs it seems very common.

 

[Greek God]

Thanks Guys
I have tried two or three start cycles to no avail.
Star just comes up with Lin Bus fault. But no other symptoms.

2009 W211 E280 Avantgarde 152k

 

[e280x]

Have you checked all the outputs and the voltage etc from the relay.
Just by unplugging the relay you can check all the plugs are working and have continuity and that the relay is providing current on all of the plug outputs. The chunky plastic plug that clips from the relay has connections that lead to each and every glow plug so it saves you trying to get past all the components etc.
Might want to use a hair drier to heat up the plastic plug as they tend to get brittle and break easily.
See my notes and pics above.

You just need to know how to use a multi meter and the pics above will be able to act as a reference.
After resolving the problem you may also need to clear the code. My flashing light just went away after replacing the faulty plug.
I believe 2 plugs need to be faulty before the light comes on.

Let us know how you get on

 

[OneForTheRoad]

Im selling a used module from my 08 cls. Only £30 if interested.

 

[zipdip]

If you do remove these hard to get at plugs,I would suggest you blow the area out with compressed air lots of crude can be down there,also the Icarsoft reader has always told me what glow plug is at fault,the fact that nothing is coming up,must mean the problem lies elsewhere,not a bad idea about the alternator.