X-90 (2WD) L4-1591cc 1.6L SOHC MFI (1997)
7) Start engine and check that voltage is lower than 5V and it rises as engine speed increases.
(Reference data: 1.7 - 2.0 V at specified idle speed)
If check result is not as specified above, cause may lie in wire harness, coupler connection, MAF sensor or ECM (PCM).