Typically glow plugs are more or less gone at 100,000 miles. The ECU will give a DTC only after all plugs are defective. The engine will start w/o difficulty up until -10C even w/o glow plugs. So -if the plugs are original- start by having the plugs replaced. Replacement is also doable for a DIY guy:
This video will show you how to replace all four spark plugs in your 2012-2018 Ford Focus with the 2.0l engine. Spark plugs were purchased from Amazon and IFord different models with 1.6 8V TDCi engine (to remove injectors plastic intake manifold needs to be removed first) Ford all models with 1.8 TDCi engine Ford all models with 2.0 TDCi engine Ford Transit with 2.0 Euro 6 TDCi engine Ford Transit with 2.0 Euro 6 TDCi engine Ford Transit with 2.2 / 2.4 TDCi engines
FORD FOCUS 2.0L DURATEC ENGINE SPARK PLUGS REPLACEMENT. Everything you need to know how to replace spark plugs (and ignition coils) on Ford 2.0L 16 valves DU
From the world’s No.1 spark plug manufacturer you’d expect nothing but the best from their glow plugs too; and you’d be right. Ngk have been relentlessly developing engine pre-heating technology since the early 1960s and the inbuilt advanced technology ensures that automotive engineers can get the most out of their engine designs and help them meet the increasing emission targets
5 days ago · FORD FOCUS II Station Wagon (DA_, FFS, DS) 2.0 TDCi Estate Diesel 07/2004 01/2008 FWD 16 136 100. Glow Plugs Set 4x fits FORD FOCUS C-MAX TDCi 2.0D 03 to 07 Bosch 1231944 1313809 | eBaywhen i get a chance i'll post a pic of the one from my mk6 its a large round multi plug to connect it to the main loom, then its the injectors, glow plugs and a red connector going to a sensor of some sort. all a single piece being one of the things im thinking of changing if i end up making a loom. separate them to make it easier should something on there need changing/repairing in the futureHapgBu.