Alfa Brera ECU Fault Lock Stumps Owners

I had a very similar issue with my Alfa Romeo 159 (2007, gasoline). Having some experience with car electronics, I first tried the basic steps like disconnecting the battery for 30 minutes to reset the control unit, but the fault codes kept returning. The root cause turned out to be undervoltage in the vehicle electrical system, which was causing the active memory to lock up. The workshop found that the voltage regulator in the alternator was failing, causing inconsistent power supply to the ECU. Total repair cost was 240 Euro, including diagnostics and parts. The symptoms were exactly like yours, persistent fault codes that wouldn't clear, though the engine ran fine. The memory lock situation is actually a safety feature to prevent data loss when voltage is unstable. Before suggesting more specific solutions, could you share: Which specific fault codes are you getting? Have you noticed any electrical issues like dimming lights or slow starter? Does your battery hold charge well? When was your alternator last checked? The auto repair process might differ based on these details, as ECU behavior can vary even between similar models.

Thanks for sharing your experience. Last service was done at 53000 KM. The fault codes in my case are P0135 and P0141, which appear to be O2 sensor related. No electrical issues noticed, lights and starter working fine, battery is strong and was replaced 8 months ago. Alternator was actually tested during my last service and checked out normal. I tried similar active memory reset attempts through automotive diagnostics but getting the same locked ECU issue. Given the consistent O2 sensor codes and the fact that all other electrical systems are working properly, I am wondering if this could be a wiring harness problem rather than a power supply issue. Anyone dealt with harness problems causing locked fault codes on their Brera?

Since my initial diagnosis on the voltage issue with my 159, I actually encountered something similar with O2 sensor codes later on. After ruling out power supply problems, a deeper ECU diagnostics scan revealed corrosion in the wiring harness connector to the O2 sensors, creating false readings that triggered the fault memory lock. The active memory kept these codes stored because the ECU was detecting intermittent connection issues. In my case, cleaning and resealing the harness connectors at the O2 sensors resolved the locked fault codes. The repair cost was around 180 Euro, mainly for labor since no parts needed replacement. Your P0135 and P0141 codes match the pattern I experienced, both pre- and post-cat sensor circuits showing issues simultaneously often points to a shared wiring problem rather than failed sensors. Given that your electrical system is healthy, I would focus the auto repair investigation on the harness connections first. Worth checking if there is any visible damage or corrosion where the harness runs near the exhaust manifold, as heat cycling in that area can deteriorate the wiring insulation over time.

Thanks to everyone who shared their experiences. After reading the responses about similar computer system issues, I performed a detailed check of the wiring harness near the O2 sensors today. Found significant corrosion on both sensor connectors, which explains the persistent P0135 and P0141 codes. The automotive diagnostics testing route helped narrow down the issue, definitely not alternator or battery related as initially suspected. Planning to take it to the shop next week to have the harness connectors cleaned and resealed. The 180 Euro estimate shared here seems reasonable for the work needed. Really appreciate the guidance on checking the wiring first before jumping to more expensive repairs. Will update the thread once the ECU diagnostics are clear and the repair is complete. This should help others who encounter similar locked fault codes on their vehicles.