Greetings!!

I have few questions about volvo SRS system, I hope someone in this forum has some answers.

The problem is irrational srs light behavior. Situation is this, SRS light is on and I cannot read any fault codes from the SRS unit. I have tried to read the codes from socket B5 on diagnostic unit side B. Diagnostic led lights when I push the button, nothing further happens, not even 1-1-1 no fault code??

I checked all the connectors between B5 terminal and crash detector unit, circuit seems to be ok. SRS manual says that voltage should be measured between terminal B5 and ground. So I measured it and it was aprx 10 volts. Manual says that if voltage is around 10 volts -> replace diagnostic unit. If less than 10 volts -> check circuit for shorts or breaks. I don't know if there is any use to replace diagnostic box, because I am able to read codes perfectly from side A-connectors (ignition, fuel injection). I guess I have to do resistance check for those few other wire which goes to alternator D+, etc. Probably have to check crash det. unit grounding too.

If those connections are ok, is there a possibility that there is something wrong in instrument cluster? is there any specific component to replace?

Since the options are running short, I am beginning to suspect faulty crash detection unit, hence the next question is. Are those crash detetector boxes interchangeable? there is little differences in model numbers on top of the box, but othervise they seem to be similar.

Has anyone tried to mix those boxex together?

Kind regards.

-Merl1n