P1670 indicates that a communication error has occurred between the PCM and the IDM.
-- Open fuse
-- IDM relay
-- Open or shorted IDM enable circuit
-- Open/short in EF circuit
-- Open/short in FDCS circuit
-- IDM powering circuits
P1280 indicates injector control signal circuit out of range low.
-- biased ICP sensor/PCM
-- open ICP sensor circuit
-- short to SIG RTN or PWR GND on ICP sensor circuit
-- open in VREF circuit