Volvo 850 Service reset Tool

[Merc85]

Only because i've heard you need the service reset tool to take the light off the Dash.

But i Bought a 850 T5 obdII with 154k on the clock, when i picked it up there was no service light ON, after few days, i changed the oil and filter, and started the Car. the service light flashed for a few minuets of driving then went out until the next time i stopped and drove it again.
this obviously went on for i little hile as it didn't bother me, but then i got a CEL light after replacing many things the light cel light and service light didnt go out.

Well when i changed the entire PCV system and Vac lines over the course of 3 days i had the Battery disconnected, (3 Days dont laugh) i restarted the engine and the CEL light and Service light goes off immediatly after start up, why is this? i'm not moaning just wondered if anyone has experienced the same?

[acshortt5]

Originally Posted by Merc85

Only because i've heard you need the service reset tool to take the light off the Dash.

But i Bought a 850 T5 obdII with 154k on the clock, when i picked it up there was no service light ON, after few days, i changed the oil and filter, and started the Car. the service light flashed for a few minuets of driving then went out until the next time i stopped and drove it again.
this obviously went on for i little hile as it didn't bother me, but then i got a CEL light after replacing many things the light cel light and service light didnt go out.

Well when i changed the entire PCV system and Vac lines over the course of 3 days i had the Battery disconnected, (3 Days dont laugh) i restarted the engine and the CEL light and Service light goes off immediatly after start up, why is this? i'm not moaning just wondered if anyone has experienced the same?

You probably had a vac leak - which you managed to fix while doing the PCV. Some fault codes will clear themselves after several driving cycles. In this case you probably had a vac leak so the ecu had to alter the fueling in order to maintain its Lamda 1.0 target, it altered the fueling outside its set parameters so it threw a fault code and set the light on. Once fixed the car would go back to normal fueling which the ecu would record and then clear the previous fault code (and turn off the dash light). Service light normally comes on when the engine is started and goes off after 30 seconds. It isn't connected with the engine management light, or shouldn't be anyway. The service light normally needs a tool to reset it.