Vito '05 109 cdi glow plug circuit

[steventux]

Hi all,

I've recently bought an '05 Vito 109 cdi and the glow plug light comes on after starting (starts no problem) for 60 seconds then goes out. This doesn't happen on warm start.
I recently replaced the glow plugs with Denso plugs from a reputable supplier while I was servicing the vehicle.
The engine warning light came on after replacing plugs. It only comes on 30 seconds after the first startup of a 24 hr period.
My local garage diagnosed the fault code as the glow plug relay. They replaced the unit and the engine warning light is gone but the glow plug light still comes on for 60 seconds after starting.
In short I've replaced everything in the glow plug circuit to no avail. I've checked connections and wiring for signs of wear/shorting but everything looks in good order.
Yet to do a resistance test on the plugs but wondering if the light might indicate anything else?

 

[sparkydude]

Posted from another forum



if it lights with the ignition... goes out after approx 2 seconds and stays off.....it's

ok

if it lights with the ignition... and stays on all.... you have a fault in at least 2

glowplugs or the relay (next to radiator.. the thick wire snaps off)... if only 1 faulty

glowplug it will not show up.

if it lights with the ignition... goes out after approx 2 seconds and then comes back

on.... you have or have had an immobiliser fault, likely cause is faulty or wrong key..

or someone has tried the door locks

it gets confusing because they use the same lamp for 2 completely unrelated faults...

the lamp re-lights and stays on to show the fault happened in the immobiliser /

locks.... it does NOT clear when the fault is fixed (if it did reset, you would be

unaware it happened)

it should be reset on a star machine.... although it MIGHT clear after a long period

(but not often)...

There is a trick.... the memory used for this fault is the same memory used for limp

mode....

if you force limp mode, by disconnecting a sensor for example, the limp mode is written

over the immobiliser fault.... when limp mode is then fixed (re-connect the sensor) the

whole fault sequence resets (it often takes a few journeys for this to happen)

I removed the connector from the air hose across the top of the engine for a couple of

days.... when reconnected it cleared in 4 short journeys


credit to Malcolm


Nick

 

[steventux]

Thanks @sparkydude, I'd read this post before with no small amount of scepticism. It feels risky to purposefully put the vehicle in limp mode in order to clear a diagnostics code.
Any merc immobiliser experts out there who can confirm this advice?

 

[sparkydude]

could always give Mark a ring at replacementmercedeskeys.co.uk what he does not know about MB immobilisers is not worth knowing .

Nick

 

[steventux]

nice one @sparkydude, will do that.