Code 77:

OxygenSensorInputHigh
O2 sensor SECM driver signal is shorted to power

Check if O2 sensor is shorted to +5VDC or Battery.
O2 (SIGNAL) PIN B to SECM PIN 3
(AFRTrimValveLowerDC fault should also occur)
Verify O2 sensor heater circuit is operating by measuring circuit resistance (2.1Ω +/-0.4Ω)
O2 PIN C (HEATER GND) to PIN D (HEATER PWR)

Cose 42:

EST1Low
Coil driver signal low or under- current

Check coil driver wiring and connector for shorts
SECM PIN 7(EST1) to COIL PIN A
Verify GND on COIL PIN B Verify GND on COIL PIN C Verify GND on COIL PIN D Verify +12vdc on COIL PIN E
To check the Smart Coil internal circuit disconnect the coil connector and measure the resistance from pin to pin