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