GMC Sonoma Navigation Fault Points to ECU Troubles

Had almost the same issue with my 1998 GMC Jimmy last year. With some experience working on cars, I initially thought it was just a loose connection, but it turned out more complex. The symptoms matched yours exactly, navigation system failure and multiple electrical fault codes. After a thorough diagnostic check, the workshop found the control module needed a complete software recalibration. The original software had become corrupted, causing communication issues between different control units. The fix involved a complete software reset and software update of the main control module. The technician mentioned these issues often stem from voltage fluctuations or incomplete previous updates. The entire process took about 2 hours and cost me 240 Euro. Before suggesting specific solutions, could you share: Any recent electrical work or battery replacements? What specific error codes are you getting? Are there any other electrical systems affected besides navigation? Does the issue occur more frequently when the engine is hot or cold? This information would help determine if your Sonoma is experiencing the same software bug mine had.

Thanks for the detailed response. To add to the discussion, last service was just 2 months ago where they performed a standard maintenance check. No electrical work was done then. The onboard diagnostics is showing error codes P0350 and P0320, mainly pointing to ignition system issues. Besides the navigation, Im now also noticing occasional dashboard flickering, especially during cold starts. This makes me think its beyond just a navigation system problem. After reading about your experience with software recalibration, Im wondering if I should request a full ECU diagnostic scan before any repairs. The control unit issues seem very similar to what you described. A voltage test might be worthwhile too, considering these problems typically show up during cold starts. Will update once I get more information from the workshop.

Thanks for providing those additional details. The error codes P0350 and P0320 combined with dashboard flickering actually confirms my initial suspicion about the control module issues in these models. When my Jimmy showed similar symptoms, the voltage test revealed unstable power supply to the main control unit. The dashboard flickering during cold starts is particularly telling, its exactly what happened in my case before the complete software reset was performed. The control module in these models can develop software malfunctions that manifest as ignition system codes, even when the ignition components are fine. A standard maintenance check wouldnt catch this since it requires specific diagnostic equipment to identify software corruption. Based on my experience, definitely push for: 1. Full control unit diagnostic scan 2. Voltage output testing across all circuits 3. Software update check for the main control module 4. Testing of communication between different control units Skipping straight to component replacement without addressing potential software issues could be costly and ineffective. The control unit might just need a proper software reset and recalibration, similar to what solved my problems.

Thanks everyone for the input. Based on the symptoms and especially after hearing about the similar ECU problems with the Jimmy, I feel more confident about the direction to take. Just scheduled an appointment for next week. Asked specifically for a complete control module diagnostic and mentioned the software reset possibility. The workshop confirmed they have the right diagnostic equipment for these model-specific software issues. Really appreciate the detailed breakdown of the testing process. Will make sure they check all those points, especially the voltage testing since the cold start symptoms match exactly. The technician agreed a full software recalibration might be needed before replacing any parts. Will post back with results after they complete the diagnostic scan and determine whether its truly a software corruption issue requiring a reset. Hoping its just a control unit software problem like in your case rather than something more serious with the hardware.