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Matt
Matt, Mechanical Engineer
Category: Mercedes
Satisfied Customers: 21879
Experience:  BEng hons Mech engineering, in auto industry 22 years
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My ml 320 cdi glow plug light will not come on so engine

Resolved Question:

My ml 320 cdi glow plug light will not come on so engine will not start.
Submitted: 1 year ago.
Category: Mercedes
Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Expert:  Matt replied 1 year ago.

Hello

I'd check that you're getting full power to the glow-plugs, they pull a lot of current so take care when checking but see if the relay is clicking when the ignition is turned on first and also check the fuse if this is OK check to see if the engine earth strap is also OK.

If the plugs haven't been changed in the last 20K then they may have to be replaced.

You can test the glow-plugs with a multimeter by measuring the resistance across the plug ( between the power connection and the body) it should be around 4-8ohms if its tending to infinity / open circuit the plug is faulty or by using a clip on current clamp, either on the supply wire to glow plugs or onto engine earth, with glow plug light on you should see 15-20amps for each glow plug fitted, 4 cylinders would be approximately 60-80amps.

Customer: replied 1 year ago.
We have undertaken all the checks suggested. The fault is intermittent. When the fault is on there is no current to the relay and plugs. We have checked the relay, earth strap and glow plugs and they are all fine. The glow plugs and relay were replaced less than 2000 ago. Any other suggestions for checking?
Customer: replied 1 year ago.
The fault codes received were C100 and D10B - both " No CAN message was received from control unit Engine management".
Expert:  Matt replied 1 year ago.

Ok

thanks for the extra info

I'd consider replacing the glow plug module

The original part number is(###) ###-#### ***** is replaced by a new part number(###) ###-####and can purchaseed from http://www.genuinemercedesparts.com

Customer: replied 1 year ago.
Posted by JustAnswer at customer's request) Hello. I would like to request the following Expert Service(s) from you: Live Phone Call. Let me know if you need more information, or send me the service offer(s) so we can proceed.
Customer: replied 1 year ago.
In April I had a "check engine" warning light come on that was solved by replacing the glow plug part number A 642900 58 01. Is that not the same part that you are referring to?
Expert:  Matt replied 1 year ago.

Hello

yes that is the same part

OK if thats fine then I'd check the wiring and connection to this part as they can collect water in the back of the connection which then shorts them out

also worth checking the cleanliness and tightness of the earth connections to the engine and battery

Customer: replied 1 year ago.
We have done the checks but the fault remains. Any other thoughts?
Expert:  Matt replied 1 year ago.

OK

are you getting any power to the plugs? as this will show if the module is being poowered up or not

Expert:  Matt replied 1 year ago.

if there's no power coming in then I'd suspect either the ECU isn't switching it on so next check the condition of the fuses for the ECU ( also called the ECM or PCM) and for the glow plugs

if these are all intact and you're confident the earths are all OK then the ECU may have to go off for testing as the next step

Customer: replied 1 year ago.
Please bear with me for a while before we close out. You did not respond specifically to the meaning of the two fault codes I gave above. What do they mean in terms of limiting the fault?
Expert:  Matt replied 1 year ago.

Hello

the fault codes

ETC – Electronic Transmission Control

Event C100 – No CAN message was received from engine management control unit.
Event D10B – No CAN message was received from engine management control unit.

so event logs like this are separated into different areas and in this case originate from the transmission

a lack of communication usually means a wiring fault between the ECU and transmission so the non start could well be down to this issue and it would be worthwhile disconnecting and cleaning the gearbox electrical connections

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