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Flashing Glow Plug Light - unable to diagnose

Posted: Tue Jul 01, 2025 9:54 pm
by BaileyBongo
Evening all, just got back from Glastonbury and have a bit of an issue with the Bongo.

We've had it before as well but I really want to sort it now as we've just had a new head gasket on it and loads of welding thanks to A&S Motors in Caerphilly South Wales to get out and do some further exploring in it.

Bailey is a 1999 model(according to the paperwork) but post 2001(from the model information sheet as it's KH-SGL5) 2.5TD 4WD AFT

Situation... the glow plugs seem to begin flashing after it's been driven for about 50 miles and it then becomes susceptible to stalling and a loss of power at low speed (traffic etc.). Meaning having to start again which is a laboured(and dangerous) when on the M5 yesterday but fine when driving at speeds and up at higher gears.

It does seem to happen more when the cigarette lighter is used to charge a phone and I've also noticed that the scavenger fan doesn't seem to be working (which I would have expected to kick in when on long journeys)

I have tried a few different things including cleaning the banjo filter, started using Millers Oil(but only used it once so far) and drilling a small hole in petrol cap(as that did seem to have a vacuum within it when unscrewed and we'd stopped)

I am struggling to diagnose it as the biggest issue is I am in no way a mechanic, but also..
  • If it is pre-99 it only comes on when driving for about 50 miles
  • If it is post-99 there doesn't seem to be any pattern or sequence to follow and just a steady on and off
It has a leisure battery fitted and that does seem to get pretty flat even when regularly plugged in to charging and even when I have attached a battery charger directly.

Any help would be greatly appreciated

Re: Flashing Glow Plug Light - unable to diagnose

Posted: Wed Jul 02, 2025 4:46 am
by gilly99
First step is to diagnose the problem. The members area gives details of how to connect into the ECU to trigger the diagnostic code sequence of the flashing glowplug dash warning light. It's easy, but be careful as the ECU is very expensive. The problem is unlikely to be the glow plugs themselves.

It sounds like you are going into limp mode after driving for a while - that's a fairly common issue (ie flashing glowplug warning light) and it's to protect the engine, but you need to find the source of problem.

One you have the diagnostic codes, then decipher them....
http://www.philmcfadden.co.uk/MazdaDiagnosticBox.htm

Edit: sort the leisure battery problem first. Any sort of battery problems can play tricks with the ECU and trigger warnings.

Re: Flashing Glow Plug Light - unable to diagnose

Posted: Wed Jul 02, 2025 10:16 am
by WestyK
I wonder if you are using a Swap loom to move devices like radio, cigarette lighters and interior lights to the leisure battery.
If you are this also moves some of the ECU power I believe. so if your Leisure batter is going flat that would cause all sorts of issues as Gilly99 says.

It sounds like your leisure battery may not be charging when the engine is running so I would test this with a multimeter first. You should see over 13.5v preferably higher but no higher than 14.4v when the engine is running.
If you don't see that then you have a fault with the split charge system. most likely just a blown fuse.

You may also fine the battery is on its last legs but check its charging first :-)

This may not be your issue but think its a good starting point as it needs to be checked anyway.

the only other thing I can think of that could cause an issue when warm is a faulty crank sensor or temp sensor but I wouldn't change these without checking the Leisure battery first.
by the way don't worry about the scavenger fan. It hardy ever runs on mine and think its only really designed to run when stuck in traffic for a long time so the engine bay gets some cool air. If your moving it wont come on. (in my experience at least)

Re: Flashing Glow Plug Light - unable to diagnose

Posted: Wed Jul 02, 2025 12:10 pm
by Ian
To establish whether your Bongo is pre or post 99, let us know the 6 digits after SGL5. This will be the full chassis number and we can determine the manufacture date.

Re: Flashing Glow Plug Light - unable to diagnose

Posted: Wed Jul 02, 2025 7:09 pm
by BaileyBongo
gilly99 - Thanks, multimeter on the way so that'll be something for the weekend. Try and diagnose the issue

WeskyK - The leisure battery does power what you mentioned and it went flat before(I think when it was in the garage and having quite a bit of work) and I fully charged it back and then came radio etc.
I have fully charged it now and fully charging the main battery as well, the relay(I think that's what it is anyway) has a permanent green light on as it's charging.
Again, something to try when multimeter is here.

Ian - 400011 is the number.

Re: Flashing Glow Plug Light - unable to diagnose

Posted: Wed Jul 02, 2025 9:54 pm
by g8dhe
When the LB goes flat (or disconnected) the ECU looses its settings and hence when the LB is recharged the ECU reports the error but there is no code for it as its loss of power! In that situation take it for a run and then the second time of starting it should be fine. However this type of problem above doesn't match the original report as the error lamp started flashing after 50 miles or so, that will be something else which can be read from the diagnostics panel.