Suzuki Ciaz Diesel Glow Plug Warning Signs & Smoke

Had similar issues with a Suzuki Swift diesel from the same generation. The constant preheating lamp combined with check engine light pointed to a faulty heating module in the preheating system. Initially suspected a simple relay issue, but diagnostic testing revealed the car preheater control unit had deteriorated connections. The car electronics showed multiple error codes related to the glow plug system. After thorough testing, we found that corrosion had damaged the main preheating unit wiring harness. The repair required replacing the defective part, specifically the entire preheating control module along with the wiring harness. This was quite a serious repair as the heating module is a critical component for cold starts and proper engine function. The smoke during acceleration was indeed connected to incomplete preheating cycles causing poor combustion. Once the car electronics were restored with the new components, both the smoke issue and warning lights resolved completely. Would strongly recommend getting a specialized diagnostic test focused on the preheating system rather than relying on general fault code readings. The symptoms match exactly what happened in my case, suggesting your preheating unit likely needs replacement.

Thanks for that detailed explanation of the preheating control unit replacement. My Ciaz had nearly identical symptoms last winter. The ignition system was really struggling and the smoke was quite bad at first acceleration. Had it fixed at a shop that specializes in diesel control units. The vehicle heater module needed a complete replacement, just like in your case. Would be interested to know what repair costs you encountered and if the fix has held up well since then? In my situation, they also found some minor issues with the glow plugs while doing the work.

Thanks for asking about the repair costs. Good news is my preheating control unit defect was actually less severe than initially thought. The mechanic found it was just a damaged cable connection causing the ignition system problems, not a complete unit failure like yours. The repair bill came to 95€ to fix the defective part connections. Much cheaper than a full preheating unit replacement. Since having the cable issue fixed, the vehicle heater system has worked flawlessly, no more smoke issues or warning lights. A thorough engine preheat diagnostic test helped identify the exact problem. Sounds like you had more extensive work needed with the glow plugs. My repair has held up perfectly for over a year now, with reliable cold starts and proper engine function throughout. Hope that helps compare repair experiences. Always worth finding a shop that really knows diesel control systems for these kinds of issues.

Thanks for the input. After reading about similar experiences, I decided to take my Ciaz to a diesel specialist last week. Got charged 450€ for a complete preheating unit replacement plus labor. The electrical fault turned out to be more complex than just bad wiring. The mechanic showed me the old heating module which was completely shot. Several components inside were corroded beyond repair. They also found two bad glow plugs while doing the work which explained the smoking issue. The engine preheat system now works perfectly, no more warning lights or smoke problems. Cold starts are much smoother too. Glad I found a proper specialist instead of the previous shop that missed these issues. The car runs like new again. Just wanted to close the loop on this in case anyone else runs into similar preheating problems with their diesel. Getting a proper diagnosis from someone who knows these systems is definitely worth it.