ŝĂŐŶŽƐƟ Đ ŽĐƚŽƌ 28 November 2026 ǁǁǁ͘ ĂŌ ĞƌŵĂƌŬĞƚŽŶůŝŶĞ͘ ŶĞƚ The Diagnostic Doctor tackles a Mini with a lack of power This month, the Doctor faces an issue that initially looks like an electronic fault, but turns out to be mechanical. If you have a diagnostic dilemma for the Diagnostic Doctor to explore, head over to the Aftermarket website at tinyurl.com/DDoc1026 where you can share the details. A2006 Mini Cooper S came into the workshop presenting with a lack of power, the engine warning light illuminated, and a noise coming from the front end. An initial pre-scan revealed the code: DTC P1688 – Electronic Throttle Control Monitor Level 2/3; Mass Airflow Calculation Initial diagnostic path Technical Service Bulletins relating to this DTC identify possible causes, which include an air leak in the induction system, implausible MAP sensor readings and failure of the supercharger bypass valve (sticking operation). When performing a DIS/GT1 test module, the guided diagnostic path can indirectly lead towards replacement of the DME control module, rather than identifying the true root cause. A correct diagnostic step at this stage is to check the operation of the supercharger bypass valve, use a handheld vacuum pump to actuate the valve and confirm smooth, consistent operation Top Repairs insight Analysis of Fast-Track Top Repairs data, available on Snap-on’s APOLLO, TRITON and ZEUS diagnostic platforms through the Fast-Track Intelligent Diagnostics Workflow, shows that, for this fault, the most common repair is replacing the harmonic balancer, typically around 100,000 miles. This points towards a mechanical issue rather than an electronic fault.
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