Engine Management Light comes on after 3 to 5 days

[BigBudda]

Evening all, I need some help please. I have just bought a 54 plate 1.4L D4D Yaris. Great car apart from a slightly annoying issue(to me anyway) The engine management light came on and it cleared OK. Approximately every 3 to 5 days(at the moment) it comes back on and needs clearing again. It is showing a code of P0380 Glow plug/heater circuit "A" malfunction. The car starts fine and runs well when cold/hot and in the latest really cold weather we have had. No smoke either. At no specific time of starting the engine in these 3 to 5 days, the light goes out after starting(as it should) but about a minute later with the engine running/driving the light comes on and stays on until cleared. It clears fine for another few days. I've tried another glow plug relay(no change) and don't like the thought of changing the glow plugs,  they probably will not come out too easy but I'm not convinced they are at fault. The bus bar linking the glow plugs looks OK to me. I have also read online of people doing all these things and the fault remains. It was also mentioned about a Toyota software update that may have been missed that could repair the fault. If anyone can help, it would be much appreciated. Thank you

[Madasafish]

Faulty glow plugs..  Had the same problem. There is a recent guide to replacing I have written in last 2 weeks.

"

Glow plugs. Just replaced ALL ours last year - failed after 14 years.They do corrode near the junction with the cylinder head and the threads do fill up with carbon and if NOT VERY careful, you may strip the threads in the head removing them.

WHat I did was: 1. clean around threads using pipe cleaner. Soaked for 24 hours using Plus Gas rusty thread Remover ( or use vinegar). (DO NOT USE WD40). Do not start engine as it will evaporate all liquid. SLOWLY rotate each glow plug until tight,retighten one turn, add more Plus Gas, untighten,   and so forth. Trying to force the thread or speed up will strip the thread. I cleaned up dirt on the way with heavy duty blue towels..(ex Halfords) - very important when you remove plug eventually - you don't want dirt getting into engine.

Cover threads with Copperease when you replace"

NOTE:

You can test for individual failure by removing the bus bar and measuring resistance from top of plug thread to engine. If it's infinite, plug is faulty. But once one goes the lot tend to go. I had two faulty ones , replaced those and the other two failed in another fortnight!!!!

 

I replaced plugs one at a time, leaving no open holes for dirt to enter.

[BigBudda]

Hi Madasafish

A BIG thank you for the information/help, looks like when I’m feeling brave I will be doing the glow plugs otherwise the fault will bug me all the time I have the car. Although I do own a diagnostics code reader and it takes minutes to clear every time but that to will end up annoying me in the end, watch this space. 👍🏻

[Madasafish]

Just take your time and you'll do fine...

 

[alan333]

There's another way to test glow plugs: Remove the bus bar, take a jump lead (or any reasonably heavy piece of wire) from the poz Battery terminal and skiff it against the connector on the top of the glow plug.  If you get a big juicy spark the plug is working, if it's a wimp of a spark (or no spark at all) the plug is knackerd.  If you can't get the jump lead to the top of the plug hold a screwdriver on the top connector and touch the jump lead against the screwdriver shaft.

[BigBudda]

Thanks Alan333, with you on that one, appreciate your ideas 👍🏻