Mazda CX7 Diesel 2007: Persistent Check Engine Light, Black Smoke, and DPF Regeneration Issues

Hey! A couple of months back, my 2004 Mazda BT-50 had similar symptoms. The issue turned out to be the wiring harness from the glow control unit to the engine control unit. It had been damaged. Although progressive, it was a substantial issue and it impacted the engine's functionality quite a bit. That annoying check-engine light was glued on like a leech. My mechanic, lovely chap, had to replace the entire wiring harness and reprogram the Engine Control Unit (ECU). Also, if your DPF regeneration is messed up as you said, that might add a bit more to the work. Be prepared, it's not a simple let's-change-the-spark-plug affair, but necessary. Defective wiring can really mess up your ride if left unattended. I'd recommend hunting for a more reliable mechanic. Cheers!

Hey there, Wow, sounds like you really had a wild ride with your BT-50. Would you mind sharing how much damage it did to your wallet getting that wiring harness and ECU reprogrammed? Just trying to mentally prep myself for what I might be in for! Also, now that a couple of months have passed since the fix, have you stumbled across any other surprises or things have been smooth sailing since then? Cheers for the help!

Hey! Ah, the damage to the wallet, never a fun topic, right? Well, the repair of that darn wiring harness from the glow control unit to the engine cost me 395.00 €. Yes, it's a bit of a sting, but trust me on this, it's worth every penny. Since the fix, I should say, my BT-50 is running pretty smoothly. No nasty surprises so far. The glow plug malfunction was sorted and that particular hassle seems to be history, thankfully! No strange lights, no frustrating cold starts, which is a big win needless to mention the smoke is also gone for good. All I do now is just regular check-ups and servicing only when necessary. Seems like a sunnier side of the journey from here. I'd highly recommend you get it checked out sooner than later, my. Those little warning signs can snowball into bigger issues, if not addressed. Keep us updated and best of luck! Cheers!

Thanks! I appreciate your frankness about the cost. It's a bit of a hit, but you're right - can't have the ol' Mazda falling apart on me. Best to get it sorted before it turns into a money pit. Good to know your BT-50 is performing well since the fix, gives me hope for mine. Some great advice there, will definitely hunt for a more reputable mechanic and get my CX7 checked out ASAP. Will keep you updated once I’ve got news. Many thanks for the input! Cheers!