You never know what you’re going to find when someone brings their car in with the check engine light on. When you get a bunch of codes you know you have your work cut out for you. Follow this Real Fix to see how a series of codes on this Volkswagen Jetta were diagnosed leading to a repair that might be unexpected.
Vehicle
2005 Volkswagen Jetta 2.5L
Title
Codes 16795, P0171, P0411, P0507 & P2279, Replaced Valve Cover
Complaint
The customer states the check engine light is on.
Cause
Connected a scan tool and found codes: 16795 – Invalid Data Received from Transmission Control Module; P0171 – System Too Lean (Bank 1); P0411 – Secondary Air Injection System Incorrect Flow Detected; P0507 – Idle Air Control System RPM Higher Than Expected and P2279 – Intake Air System Leak. Performed a visual inspection of the air intake system, code related components, and code related electrical connections and vacuum hoses and found the secondary air injection vacuum supply hose was disconnected. Connected the secondary air injection system vacuum supply hose, started the engine with the scan tool connected to monitor live data and found the engine specified 680 RPM engine speed was above specifications. Removed the engine oil dipstick and installed a vacuum gauge into the dipstick tube and found the crankcase vacuum was above specifications. Removed the crankcase ventilation hose from the valve cover, plugged the hose and found the engine idle speed returned to 680 RPM. Reinstalled the crankcase ventilation hose to the valve cover. Connected the smoke machine to the engine air intake system, induced smoke into the air intake system and found smoke leaked from the engine oil dipstick tube with the dipstick removed. Removed the valve cover for inspection and found the crankcase ventilation valve diaphragm was damaged. The crankcase ventilation valve is integrated into the valve cover and is replaced as an entire unit. These test results verified the valve cover was faulty.
Correction
Replaced the valve cover, cleared codes, performed a road test and verified the vehicle operated properly. The check engine light did not illuminate and no fault codes returned.