VW Caddy's EGT Sensor Failure Drains Power and Fuel

I had a very similar issue with my 2018 VW Golf last year. Have moderate experience working on cars but left this one to the professionals due to the complexity of emission control systems. The symptoms you describe match what I experienced, check engine light, power loss, and increased fuel consumption. Initially thought it was just the exhaust temperature sensor, but the workshop diagnostic revealed a leak in the exhaust system near one of the temperature sensors. The leak was causing incorrect readings and making the emission control system operate inefficiently. The complete repair included: Pressure testing the exhaust system, Replacing a cracked exhaust component, Installing a new temperature sensor, Resetting the engine management system Total cost was 265€ and resolved all issues. Fuel consumption returned to normal and power was fully restored. To better assist with your specific case, could you share: Current mileage on your Caddy, Any unusual sounds from the exhaust, Whether you notice temperature fluctuations in the gauge, If there are any other warning lights The exhaust sensor placement differs slightly between Caddy and Golf models, so these details would help determine if your issue matches mine.

Thanks for sharing your experience. Just had my service at 131024km about 2 weeks ago, and everything was fine then. Since your post, I have noticed a slight rattling noise from the exhaust system, especially during cold starts. After checking the onboard diagnostics, there are no temperature fluctuations showing on the gauge, and the check engine light remains the only warning. The power loss seems most noticeable when accelerating from a stop. The heat sensor readings are erratic according to the scan tool, which aligns with the symptoms you described. Your repair breakdown is particularly helpful, as it points to a potential compound issue rather than just a faulty sensor. Will have the exhaust system checked for leaks, since the symptoms match so closely with your experience.

Thanks for those additional details. Given the timing right after your service and the erratic sensor readings you mentioned, your case sounds remarkably similar to what I experienced with my Golf. The rattling noise during cold starts is particularly telling, this was also present in my case and turned out to be directly related to the exhaust component failure near the temperature sensor mounting point. The emission control system becomes particularly sensitive during cold starts, which explains the more noticeable symptoms during this phase. Since we have nearly identical symptoms and your scan tool shows inconsistent temperature sensor data, I strongly suspect you are dealing with the same combination of issues, a compromised exhaust system integrity affecting the sensor readings. The engine management system is likely getting confused by these false readings, hence the power loss. A couple of notes from my experience: The exhaust leak worsened gradually over about 2 weeks, The engine management system was compensating initially, masking the full extent of the problem, Fuel consumption increased by roughly 15% before the repair, Post-repair performance improvement was immediate Would suggest getting it checked soon before the exhaust system damage potentially extends beyond the initial problem area. The complete repair costs might be similar to what I paid (265€), assuming the damage is caught early.

Having looked into this further and checked my scan tool readings again, I am now convinced we are dealing with the same issue. The rattling during cold starts has actually gotten slightly worse over the past few days, matching your progression timeline perfectly. Booked the car in for next week to have the exhaust system and temperature sensor thoroughly checked. The workshop confirmed they will do a complete pressure test of the system, along with a full diagnostic of the engine management setup. They estimated costs between 250-300€, which aligns with your repair experience. Really appreciate your detailed breakdown of the repair process and symptoms. It helped confirm my initial suspicion about the exhaust sensor issues while highlighting the importance of checking the entire exhaust system for potential leaks. The fact that your vehicle showed such immediate improvement after the repair is encouraging. The scan tool continues showing those erratic temperature sensor readings, and fuel consumption has increased about 20% now. Will update once the repair is complete, but feeling much more confident about the diagnosis thanks to your insights about the emission control system components.