Question about 2005 Volkswagen Passat
P0171 - Fuel Trim, Bank1 System too Lean
VW DTC 16555 (P0171) - Fuel Trim, Bank1 System too Lean
By only pulling battery power from the ECU doesn't clear the codes on OBDII systems.
You must have access to a VAS, VAG-COM, Bosch KTS, ... diagnostic scantool. The ECU (Electronic Control Unit for engine management) is seeing a fuel trim that's much too lean even with the ECU making adjustments. Colud be the MAF (Mass Air Flow) sender out of order, the pre-cat O2 sensor, or a significant vacuum leak. You need to confirm / deny working parts with a 2nd gear pull data-logging measuring blocks 002, + 032 (VAS, VAG-COM).
Posted on Dec 09, 2009
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Posted on Jan 02, 2017
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