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MechanicGreg, ASE Certified Technician
Category: Volvo
Satisfied Customers: 46
Experience:  ASE Certified. 9 years industry experience.
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2000 Volvo s40: The Check Engine light came on and I..Jiffy Lube

Resolved Question:

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?
Submitted: 8 years ago.
Category: Volvo
Expert:  MechanicGreg replied 8 years ago.


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.


Possible causes:

- 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.

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