1991 astro AWD ABS code 35 problem

Hello fellow Astro owners, I need some tech advice to a ABS problem I'm having. I've jumped out the A & H pins on the diagnostic connector and received codes 35 & 12. The chilton manual states that it is a faulty VSS sensor or the left rear wheel sensor or an open circuit in one or the other. I've measured the resistance of the VSS sensor and it is within specs.(1500 ohms) but the rear wheel sensor is 300 ohms out of spec.(1800 ohms). I have no problem with my speedometer so I'm assuming the VSS circuit is good, but I don't want to rule it out. I don't believe the rear wheel sensor is that far out of specs. to shut down the ABS system but I could be wrong. I like to know if anybody has had the same or similar problem. What was the cause and what was done to correct it. I appreciate any help. Thanks. Ron