I recently had my 93 ranger pop a code 157 which is MAF sensor below minimum voltage. i have done everything I can think of from replacing the MAF and I even went as far as to trace the wires and check for continuity all the way through and everything checked out. My battery is good to go, my charging system is good to go heck even my starter system is good to go even though it has nothing to do with the MAF. I traced the wire from the MAF all the way to its plug in the PCM and checked continuity from plug to plug with good results, I checked all 4 wires. I need to fix this issue. My truck will drive just fine but the moment I let the truck idle it starts to drop off hits 500 RPM and stalls out. i can start it just fine after ever incident of this. My only thought now is that the PCM is going bad. If anyone has ever encountered this problem and got it fixed can you please tell me what you did. I have even reset the codes but it comes back as soon as I start it up. Thank You to all those that help.