glow plugs lamp constantly illuminated

[Macadamia]

Hello all,
This morning my 3.0L TDV6 suffered a pretty average crank which I attributed to the main battery being a bit low on charge owing to cold weather, old battery and a few days without use. After it started however, the glow plug light remained illuminated, and it remained illuminated even after stopping the car. It's been driven for some time, stopped and started. Battery has been charged and is holding charge at 12.6V, the car has been turning over fine for the rest of the day and yet the plug remains illuminated.

If I read correctly, the glow plug function is not monitored by ECUs so there are no faults logged. The only thing I've really been able to check is that fuse is fine. The annoying part of it all is that the car starts fine even with both banks of glow plugs unplugged! I don't even know where to begin with diagnostic!

where should I look next?

Thanks

181872

181871

[DiscoJeffster]

I would suggest you have a faulty glow plug, shorted or open circuit. Have you read the codes (despite what you read)?

[Macadamia]

Have you read the codes (despite what you read)?
yes I have and no there are no faults

[DiscoJeffster]

yes I have and no there are no faults

Pull the connector off all of them and measure each one’s resistance to earth. Record the values and look for anomalies. Report back.

[scarry]

Not the easiest to get out,often a PITA job.

Good luck with it.

[Macadamia]

Pull the connector off all of them and measure each one’s resistance to earth. Record the values and look for anomalies. Report back.

They're all reading the same ~1.4 ohms which seems about right if they're around 9a each


Not the easiest to get out,often a PITA job.

ha! I just read through what is required and it's no easy task. Probably going to have to handball this one to the mechanic if they need changing out. hopefully, holding out for a simple fix somewhere before then though

[josh.huber]

Tool isn't set up correctly.. Mine gives me faults when I leave the connector off doing an oil change.. I've done that more then once.. Do the service go for drive. Come back do final checks.. Open circuit glow plugs..


What did you read the faults with?

[Macadamia]

Tool isn't set up correctly.. Mine gives me faults when I leave the connector off doing an oil change.. I've done that more then once.. Do the service go for drive. Come back do final checks.. Open circuit glow plugs..


What did you read the faults with?

sorry you're going to have to elaborate. And why are you disconnecting the glow plugs to change the oil?

faults read with IID, pending + confirmed + failed test all turned on. definitely no faults logged.

[josh.huber]

I don't have my IID here to check it's setup.

When looking at the engine. The left side (right side sitting in seat) connector always gets in my way so I disconnect it. I always forget to plug it back in.

Problem might be bigger if you don't get a code for them unplugged.

On second thoughts, maybe I only got the code when it tried to use them on a cold morning?

When I get my IID back tomorrow I'll remove the connector and recheck

[Macadamia]

here's a conundrum for you...

this morning, cold engine, ambient temperatures ~10 degrees, I started the car still with the glow plug fuse removed and L&R banks disconnected. Car started fine. Glow Plug lamp is no longer illuminated but this time I have a fault about glow plug control voltage.
Cleared the fault, reconnected everything, started the car - no lamp and no faults.

I have a working theory that'll take a few morning cold starts to test:

The initial lamp illumination was caused by my faltering cranking battery.
The lamp remained illuminated throughout the day, and I was getting no faults even with the plugs disconnected throughout the day, because the ECT was at normal operating temperatures after my initial drive thus on subsequent cranks the glow plugs were not utilised and so did not trigger their test cycle or monitoring or whatever it is that logs faults and illuminates lamps for them.


I guess to test this I'll have to use a camp meter around the +ve wire to each glow plug and note what they draw on a cold start vs what [if any] they draw on a warm start.

but for now all seems to be back to normal ¯\_(ツ)_/¯