VW Caddy Diagnostic Loop: Engine Light Persists

As someone with moderate experience in diesel diagnostics, I had a very similar issue with my 2010 VW Transporter. The symptoms you describe match exactly what I encountered after having some repair work done. The onboard diagnostics kept showing incomplete readiness codes, particularly after the computer reset. My workshop explained that following any diagnostic scan or battery disconnect, the vehicle needs to complete specific drive cycles to reset all system readiness monitors. In my case, no parts needed replacement. The solution was simply following a proper drive cycle protocol: Ensuring the fuel tank was between 30-70% full, Starting with a cold engine, Driving at steady speeds on main roads, Including both city and higher speed driving patterns This process took about 40-50 minutes of driving, after which the system readiness monitors completed their cycles and the check engine warnings cleared permanently. The diagnostic scan was free since I had an ongoing service relationship with my regular workshop. They confirmed no actual faults were present, it was purely a monitoring system reset requirement. To better assist with your situation, could you share: Have you had any recent repairs or battery disconnection? Which specific error codes are showing up? What type of driving have you done since the codes first appeared? This would help determine if your issue is similar to what I experienced or if there might be underlying sensor problems that need addressing.

Thank you for your detailed insights about the drive cycle solution. Just had my 130483km service last week, and they actually replaced the battery, which now explains these symptoms. The initial codes I got were P0601 and P1403, but they seem to reset after each computer reset attempt. I drove mostly short distances since then, mainly under 15 minutes per trip. Based on what you shared, it sounds like I need to perform a proper drive cycle to complete the system readiness monitors. Before jumping into sensor replacements, I will try following the driving pattern you described. The onboard diagnostics probably just need time to reestablish their baseline readings. Would you still recommend getting another emissions test done after completing the drive cycle, just to confirm everything is working correctly?

Thanks for providing those additional details about your recent service and driving patterns. Those short trips definitely explain why your system readiness monitors havent completed their cycles yet. Since I dealt with the same situation in my VW, I can confirm that getting another emissions test right now would likely fail due to incomplete readiness status. The exhaust system and its sensors need that complete drive cycle we discussed to establish proper baseline readings. After my battery replacement, I also saw similar error codes reset themselves. Once I completed the full drive cycle protocol, my vehicle inspection passed without issues. The OBD readiness monitors just needed that extended driving period to complete their self-tests. My suggestion would be to: 1. Clear the codes one final time 2. Complete the full drive cycle as previously outlined 3. Monitor if any new codes appear 4. Then schedule an emissions test If error codes return after a proper drive cycle, that would indicate a genuine sensor issue rather than just incomplete readiness monitors. But based on your description and my experience with the same model, this sounds exactly like standard post-battery-replacement behavior that should resolve with the proper drive cycle.

Based on this information, I understand better now why my vehicle inspection data kept showing issues. My short trips clearly werent enough for proper system readiness checks after the battery change. Going to carve out time tomorrow morning for that 40-50 minute drive cycle. Will ensure the tank is properly filled and follow the steady speed patterns you suggested for the car diagnostics to complete properly. The onboard diagnostics definitely need that proper baseline data after the service work. If the check engine light returns after doing the complete drive cycle, I will bring it back to have them check the sensors. But your experience matches my situation so closely, especially with the timing after battery replacement, that I am confident this will resolve the readiness monitor issues. Will update the forum once I complete the proper drive cycle and get confirmation that all systems are running correctly. Really appreciate the detailed troubleshooting steps, saved me from unnecessary sensor replacements and diagnostic fees.