code help

hi, i have a 95 geo metro lsi with the 1.3 4 cyl. i inserted the fuse in the fuse box, it flashed once, paused an flashed 3 times.it did this 3 times.then it flashed 3 times then once,it did this 3 times, then back to the 1 pause then 3 again.i checked the codes an did not find a 31! any help please!

13 is oxygen sensor, 31 is MAP sensor. Unplug all connectors under the hood and renew the grounds, main sensor and computer ground is under the intake manifold on the back side of the engine.