Various volvo models with Jetronic fuel injection, had up until 1996 a diagnostic unit which could display a flash code for what the ECU's self diagnostic system had recorded. Does anyone know what exactly is inside the diagnostic unit. The connections to the unit includes a positive lead, a ground and the diagnostic leads to the Jetronic ECU and the Ignition ECU. The unit has a pushbutton and a LED for displaying the codes. But what is the function inside this unit?
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