Hello - I recently posted a problem about my daughters 2001 Volvo S40, 4 cyl.
1.9 Liter Turbo, approx. 38,500 miles on the odometer. She came home with a MIL on : Code read was PO101 MAF or VAF CKT Range/Perf. Suggestions included a bad MAF Sensor, dirty air filter, and possibly a turbo malfunction such as the waste gate hanging up. Then another code came up within a week: PO128 Coolant Temp Below Thermostat Regulating Temp. After poking around I found an oil leak: There appears to be an inlet and return line to the turbo: The inlet line was leaking oil. The fix was a set of rubber O-rings/seals from the local dealer. Cost: $4.24. Replaced the thermostat and gasket/housing seal from the local NAPA $6.28. Total cash outlay: $10.52 Cleared the codes - good as new. Just thought regular posters might like a follow-up. Thanks for everyone's help.Unca' Bob