I have a 2000 Volvo s40. The "Check Engine" light came on and I took it in to a Jiffy Lube for service. They read the codes and were nice enough to give them to me. The codes were:P0455 "evap emission control system leak"P0128 "coolant temp. below thermostat"P0234 "engine overboost condition"P0101 "MAF or VAF a ckt range/perf"P0171 "system too lean (bank1)"P0102 "MAF or VAF a circuit low input"P0172 "system too rich (bank1)"Can you help me diagnose the problem?
Year: 2000Make: VolvoModel: S40Engine: 4 cyl. 1.9 L
Filled the coolant to appropriate level, checked the gas cap to make sure it's closed properly.
There may be a few different failures here, but it may be a one fix all. The code to start with is P0234 - engine overboost. This is a turbo related code. What can happen is too much pressure will build up and cause the MAF (mass airflow sensor) to read incorrectly. This incorrect reading can cause the rich/lean codes.
- hoses between the turbo and turbo control valve (may be damaged or restricted)
- failed turbo control valve
- failed boost pressure control valve/servo - check for no contamination/not stuck
- hoses between the intake manifold, pressure control, and turbo may be restricted/damaged
- check the maf sensor for corroded/poor connection
- if you have a multimeter, check the resistance in the turbo control valve terminals 1 and 2 - there should be about 30 Ohms; if not then replace.
ASE Certified. 9 years industry experience.