Disco 2 Won't start and GlowPlug Relay Drive Open Load fault code

Keith_L · Jul 26, 2025

I took the D2 out this morning for a 15 mile run, parked up and did my thing, and then drove back 15 miles about 2-3 hours later. Both times it started straight away as it always does. However, when I tried to start it this afternoon it wouldn't. The amber differential lock warning light lit briefly as it always does when you start up, but the engine didn't attempt to crank.

I connected my new Foxwell and checked for codes and got the following - see attached picture:

DTC - GlowPlug Relay Drive Open Load
DTC - Engine Speed outside bounds for cruise (where fitted)

It didn't give code numbers unfortunately. I cleared the codes and tried again and the same codes reappeared. I also tried the spare key just for fun but that made no difference.

I have no idea what I need to do to sort this and of course I can't drive it to someone who might. Any suggestions from anyone would be greatly appreciated. It's a 2002 Td5 automatic.

codfather79 · Jul 26, 2025

Just a thought, how good is the battery?

Keith_L · Jul 26, 2025

Thanks @codfather79. That did cross my mind but it's only 4 years old and is kept on a CTEK charger when not in use. I have a battery monitor/USB charger plugged into the cigarette lighter and that was showing 12.6V+ throughout the messing around, although I appreciate the capacity may have dropped over time. The thing is this morning it started both times straight away whereas this afternoon it made no attempt to turn the starter which is what made me think it had to be something else.

sierrafery · Jul 27, 2025

Unfortunately you can't rely on those fault codes cos Foxwell is not reliable with the Td5 engine management codes that's a verified fact,

first of all this

Keith_L said:
this afternoon it made no attempt to turn the starter ...

has nothing to do with the engine management or fault codes and if you unlocked with the fob it's not immobilised either so first of all check the battery clamps to be tight, then the spade connector on the starter solenoid as it used to get loose, if that's OK swap the starter relay and check the fuse, if no joy remove the relay and bridge the perpendicular cavities in the fusebox with a wire to see if it cranks that way... if still no effect we'll speak then but the gist is that the problem is on the starting circuit somewhere, bad contact at the fusebox plug is quite common as well

Shedload · Jul 28, 2025

Agree with Sierra, those DTC's don't really mean anything.
Have a good look around starter, just beware of live wires !
Can't recall the part name but I had the ignition barrel fail on mine which resulted in non start, but this was a gradual fail.
Just thought, the starter solenoid is a fairly easy swap, though getting the starter out can be a fiddle.

Keith_L · Aug 10, 2025

I have checked the fuse with a meter and that was okay. The relay seemed to be clicking okay but I swapped it with that for the fuel filler flap release and the flap still released and the starter relay still clicked. The +ve battery terminal is tight but I can just turn the -ve slightly if I try hard enough but I can't seem to tighten the clamp any more. It's the sort where you tighten down onto a conical clamp. The wire was still firmly on the spade connector on the side of the starter solenoid. I pulled it off and there didn't seem to be any corrosion on either half, but the half connected to the solenoid seemed to move around a bit. Not sure if that is normal or not.

All that is left is to try is the bridging you suggest but I'm not sure exactly where am I putting the bridging wire?

sierrafery · Aug 11, 2025

Keith_L said:
All that is left is to try is the bridging you suggest but I'm not sure exactly where am I putting the bridging wire?

Across the middle perpendicular cavities: 30 - 87... if it doesnt crank that way and no click from the starter solenoid measure for live on the spade , if it has +12V the starter is fubar, if no power the problem is at the fusebox or the wire to the solenoid

Keith_L · 2025-08-19T12:19:18+0100

I tried bridging 30 and 87 to no avail. Presumably I should a) be able to hear the relay clicking and b) be able to measure 12V between 30 and 87 as someone tries to start the car? Are there any other voltage checks I can do on the relay cavities?

I also tried measuring the voltage at the cable that goes into the starter solenoid but I wasn't getting a reading. I'll try again later with a more reliable earth connection.

Thanks for your continued help.

Keith_L · 2025-08-19T13:37:08+0100

I think I may have cracked it. Having check the voltages on all 4 pins of the relay it concerned me that no voltage showed on any of them even when attempting to start the engine. I rechecked the fuse and that was still okay. I was then looking at the lid of the engine bay fuse box and noticed that FL13 is marked SM / starter motor. When I checked it appeared to be broken, and a meter confirmed this.

This raises some new questions. What is a fusable link and how does its function differ from a regular fuse? Following from that, why might it have blown i.e. is it likely that if I can find a replacement it will blow again, or is there a bigger problem I need to address? I thought of swapping one of the other 30A FLs in the fuse box but decided against it just in case I ended up blowing that as well.

Edit: I have used the meter on the FL base. The connector nearest the wing is 0V relative to earth and the other is 12V relative to earth, even with the key removed. 0V relative to each other and a bulb between the two connectors doesn't light.

Shedload · 2025-08-19T15:13:48+0100

Easy bit first, fuseable link is just a fuse, often of higher ampage.
As you say the concern is how or why it blew.
Your investigations so far seem to suggest it is not going to earth, however the earth could be introduced when you try to start ?
It could have blew from repeated attempts and over heated, but you need to check for any loose wires.
Start by using your meter and check for ground/earth on the live circuit with ignition on and of to be sure.
It does not work for all circuits but a rudimentary test is to use a high Watt bulb, headlight is best, but 21W will do.
Wire this using spade connectors or thin croc' clips into the fusible link, ensuring they don't touch.
Try to start, if the bulb lights it is going to earth and further investigation is needed.

Disco 2 Won't start and GlowPlug Relay Drive Open Load fault code

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