Grounds
A properly functioning ground is one of the many requirements to have a complete circuit for electricity to flow, doing work along the way. A failed/failing ground can cause all kinds of weird issues on our vehicles.
Symptoms of grounding issues:
Completely dead vehicle or intermittent electrical problems
Turn one thing on, others turn off
False DTCs set
Dim/flickering lights/gauges
Excessive radio noise
Burnt/slipping A/C clutch
Intermittent failures/codes of multiple sensors
Hard/No/Slow start issues
Lack of charging/dead battery
and the list goes on and on
Continuity testing is often not enough, See: Voltage Drop Testing
Most common ground issues:
Start where you have last done work and check/clean/tighten connections that you may have disturbed or forgotten
Check your battery connections, usually the positive is where you have the most issues, but the ground can be a problem as well.
Double check your vehicle body and block grounds that lead from the battery
Ones that tend to rust first tend to be on the radiator core support and have seen some problems down at the fuel pump ground
Thermostat housing, corrosion and wires breaking here can be sort of common, esp after it's been removed to replace the thermostat
Examples of ground numbers-locations-functions on my 03 AWD.
G100-right front of radiator support next to the engine coolant reservoir - Front/rear washer pumps, Blower motor resistor/relay, RF park/turn lamp, R Horn, RF marker lamp, R repeater lamp
G101-left front radiator support below the main body ground - headlamp relay, BrakePressDiffSwitch, LF Park/turn and Marker, L horn, L repeater lamp
G102-left side radiator support - battery to body
G103-lower right front side of the engine block - battery to engine block
G104-lower left side of the evaporator housing behind the receiver drier - AC Compressor Clutch, Coolant Bypass Valve Solenoid, A/C Low press switch, Fuel pump/AC/Starter/Upfitter relay
G105-Thermostat housing - PCM, PNP, MAF, ICM, IPC, DLC, CCM, DIC, RearSeatAudio, AmbientAirTempSensor, Turn/Haz Flasher, shared G107 w/BCM
G106-Left rear engine block at knock sensor - VSS Shield, EBCM, Knock Sensor shield
G107-Left rear engine block at knock sensor - BCM shared w/G105
G110-Left side of engine compartment behind battery - Wiper motor/module, TCCM, CHMSL, IPC, Headlamp/dimmer switch, Tow/Haul switch, A/T shift lock control solenoid, IGN switch, IGN key alarm switch, Steering Column ground, Multifunction Turn Signal Lever, DLC, outside rearview mirror switch, Window master switch, Drivers Door lock switch, DRL relay, Seat adjuster switch, Blower motor switch aux heat, blower switch aux A/C, Vanity mirrors
G200-passenger compartment, behind the right front kick panel - Radio, Window switch front pass, rear window washer/wiper switch, engine cover ground(G201), Air temp actuator, Door lock relay, RKE receiver, Driver door unlock relay, Aux outlet front 1 and 2, cigarette lighter
G201-Behind the center of the dash - Engine Cover Ground for RF suppression
G300-passenger compartment, behind the left front kick panel - Airbag Sensing and diag module
G301-Above the rear heater toward the rear of the vehicle - Overhead console, aux heater blower motor,
G302-On underbody front side of fuel tank Fuel Pump and Sender - Fuel Pump and Sender
G303-Behind the bottom of left B pillar - upfitter connector
G400-In the upper half of the left D pillar - Overhead Console opener/lamps, Center and front Courtesy reading lamps, seat belt buckle switch, rear aux power outlet, L tail-stop-turn backup marker CHMSL, audio amp, rear door jam switch
G401-In the upper half of the right D pillar - RR turn/marker/backup/tail-stop-turn/license lamps, trailer ground
G403-In the upper half of the right D pillar - Rear window defogger grid, Rear window wiper/washer module, liftgate relay, liftgate release actuator
G404-In the rear of the passenger compartment below the left rear belt retractor - Aux A/C Blower motor