Is your machine not OBDI complient. The Volvo was an 89 version and was (first year). In which case the OBD pinged it dead on. In my case it screwed into the bell housing of the transmission. Operation and heat soak caused it to fail but would reinitialize if left to cool for an hour or so. Wasn't expensive so just replaced it.

Best of luck!

Ron

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1995 E320 -171k-km
1995 S420 -333k-km