2010 Lexus IS: Persistent Pre-Glow Light, DPF Regen Failure and Smoke Emission Issues

Hey there! I had a similar issue with my 2013 Lexus IS (diesel too) a while back. Same symptoms - black smoke, check engine light, the works. And just like yours, the cheeky glow light had a love affair with being on. Your intuition might be right; it does indeed sound like a glow plug issue. In my case, the culprit turned out to be the wiring harness between the glow control unit and engine control unit, which had got itself into a bit of a pickle. I know, sounds like a right headache! Here's what the mechanics did...they had to unfasten the glow control unit (GCUs) and engine control unit (ECUs), then inspect and replace the defective harness. From there, they reconnect everything and tested the system top to bottom to be sure. It's a bit of a tricky and solid job, can't be done by any old wrench-wielder you know. Generally, it's a serious issue if not addressed as it might lead to more engine problems down the road, especially if the wiring harness damage is severe. In my case it was more of a challenge due to the complexity of the fix, but once done, she purred like a kitten again. Hope this helps! All the best with your Lexus.

Hey! Thanks for chipping in with your insight. Sure does sound like what's going on with my IS. Had no idea it could be the wiring harness - that sounds like a real tangled mess! Just curious, do you recall approximately how much you ended up shelling out for the fix at the mechanic? And one more thing, did you experience any related issues or was it all smooth sailing after that? Cheers in advance!

Hey! Just dug out the bill from my stash. Back then, the whole process of fixing the damaged wiring harness did indeed cost an arm and a leg but knowing the fact that my car was in safe hands, it was worth every penny. The cost set me back by 395€ but hey, you can't put a price on safety, right? After the mechanic worked his magic, the glow plug issue was rectified and truth be told, not even once have I smelt any burnt rubber since or seen any additional black smoke bellowing out of my Lexus' backside. Can safely say, it's been smooth sailing and my trusted diesel beast has been running like clockwork ever since. So, don't lose hope! Just a wee bit of fixing and your Lexus will be back on the road like a champ. Best of luck!

Cheers for the quick response and sharing of your experience! €395.00, huh? A bit higher than what I had expected, but you're absolutely right - can't skimp on the safety and longevity runs. Great to hear your car has been trouble-free post the fix. Definitely reassures me and eases my mind a fair bit. I'll head into the garage armed with this new knowledge and see how things pan out for my Lexus. Thanks a ton - really appreciate it! Keep well and safe driving.