91 mazda b2600i 4x4

wondering where to plug a code reader in on my truck, it has the 2.6liter 4cy

Sorry, I do not know the answer to this one directly. If it is the same(ish) setup as the B2200, then there should be some harnesses that you can plug in the factory code reader to on the driverside kick panel under the fuse box. Do be careful as some of your relays are there as well. The only other place that comes to mind would be on the firewall under the hood right behind one of the wheel wells.

the connector is on the passenger side wheel well. you'll need an obd1 code reader or you can just jump 2 of the terminals in the connector and count how many times the check engine light flashes. i forgot what terminals though.