Browse our complete library of 100 professional automotive electrical fault diagnosis articles. Each guide includes real diagnostic procedures, technical specifications, and practical troubleshooting steps.
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Learn the professional procedure for testing automotive batteries using a digital multimeter. Includes voltage charts, load testing methods, and interpretation of results for 12V lead-acid, AGM, and EFB batteries.
Comprehensive guide to diagnosing alternator problems. Covers common failure symptoms, voltage output testing with engine running, diode ripple testing, and how to distinguish alternator faults from battery or wiring issues.
Step-by-step procedure for diagnosing parasitic battery drain (key-off current draw). Learn how to use the ammeter function, interpret current readings, systematically isolate circuits, and identify common causes of excessive dark current.
Detailed guide to testing automotive voltage regulators — both external (standalone) and internal (built into alternator). Covers voltage setpoint verification, load response testing, and troubleshooting overcharging and undercharging conditions.
Complete guide to automotive battery replacement. Covers battery group sizes, CCA and Ah ratings, BCI compatibility charts, proper installation procedures, terminal cleaning, and battery registration/reset procedures for modern vehicles with BMS.
Systematic methodology for diagnosing automotive charging system problems. Learn waveform analysis for alternator output, voltage drop testing across charging circuits, and how to use a diagnostic flowchart to isolate faults efficiently.
In-depth technical comparison of Absorbent Glass Mat (AGM), flooded lead-acid, and Enhanced Flooded Battery (EFB) technologies. Covers internal construction, charging voltage requirements, failure modes, and diagnostic considerations for each type.
Comprehensive comparison of battery load testing methods. Covers traditional carbon pile load testing, electronic load testing, and conductance testing. Includes pass/fail criteria based on CCA ratings and temperature compensation charts.
Reference guide to alternator voltage output specifications across major vehicle manufacturers. Includes nominal voltage ranges, ripple voltage limits, temperature compensation values, and brand-specific charging strategies for BMW, Toyota, Ford, Mercedes, and more.
Specialized guide for diagnosing intermittent alternator and charging system faults. Covers data logging with scan tools, capturing intermittent voltage drops, using min/max recording on multimeters, and wiring harness flex testing techniques.
Comprehensive inspection guide for battery cables, terminals, and connections. Learn to perform voltage drop tests across positive and negative cables, measure connection resistance, identify corrosion damage, and properly clean and protect terminals.
Technical guide to diagnosing modern smart charging systems where the PCM/ECU controls alternator output. Covers LIN bus communication, variable voltage strategies, regenerative charging, and scan tool data interpretation for charging system PIDs.
Complete guide to auxiliary and dual battery systems found in trucks, RVs, overland vehicles, and luxury cars. Covers battery isolator types, split-charge relays, DC-DC chargers, and troubleshooting common auxiliary battery problems.
In-depth guide to automotive Battery Management Systems. Covers battery current sensor (IBS) testing, BMS module communication diagnostics, battery state of charge (SOC) monitoring, and proper BMS reset/registration procedures after battery replacement.
Complete guide to starter motor diagnosis. Covers voltage drop testing across the starter circuit, starter current draw measurement with an inductive clamp, solenoid voltage testing, and starter bench testing procedures.
Comprehensive ignition coil diagnostic guide. Covers primary and secondary winding resistance measurements, insulation testing, oscilloscope waveform analysis for coil-on-plug (COP) and wasted spark systems, and identifying coil failure patterns.
Detailed guide to crankshaft position sensor (CKP) diagnosis. Covers inductive and Hall-effect sensor testing, oscilloscope waveform interpretation, resistance and voltage measurements, and common CKP failure symptoms across vehicle brands.
Focused guide on starter solenoid fault diagnosis. Learn to distinguish between solenoid click and starter motor failure, perform solenoid terminal voltage tests, bypass solenoid for testing, and diagnose the starter control circuit.
Systematic diagnostic procedure for no-start conditions where the engine cranks normally. Covers fuel delivery electrical checks, ignition system verification, sensor signal testing (CKP, CMP, MAF), immobilizer system checks, and ECU communication verification.
Learn to diagnose engine conditions by reading spark plug appearance. Covers normal wear, carbon fouling, oil fouling, lean conditions, detonation damage, and overheating patterns. Includes spark plug gap specifications by vehicle type.
Complete ignition switch electrical testing guide. Covers switch terminal identification, continuity testing across switch positions (OFF, ACC, ON, START), voltage testing under load, and diagnosing intermittent ignition switch failures.
Specialized guide for diesel engine glow plug system diagnosis. Covers glow plug resistance testing, glow plug control module diagnostics, timer relay testing, current draw measurement, and troubleshooting hard cold start conditions.
Detailed guide to testing starter relays and fuses in the starter control circuit. Covers relay bench testing, socket voltage testing, relay substitution methods, fuse voltage drop testing, and identifying common starter relay failure modes.
Guide to diagnosing distributor-based ignition systems found in older vehicles and some modern industrial engines. Covers pickup coil testing, ignition control module (ICM) diagnosis, cap and rotor inspection, and timing adjustment procedures.
Technical guide to diagnosing push-button start and keyless entry/go systems. Covers key fob battery and signal testing, start button diagnosis, brake switch interaction, antenna/module communication testing, and passive entry system troubleshooting.
Advanced diagnostic strategies for intermittent no-start problems. Covers using lab scopes to capture intermittent signal dropouts, fuel pressure logging, crank/cam correlation monitoring, relay intermittent failure testing, and temperature-dependent fault isolation.
Complete test procedures for zirconia and wideband O2 sensors including signal waveform interpretation, heater circuit resistance testing, and upstream vs downstream comparison strategies using a scan tool and oscilloscope.
Step-by-step guide to testing hot-wire and hot-film MAF sensors. Covers grams-per-second PID interpretation at idle and under load, MAF cleaner spray procedures, and diagnosing rich/lean fuel trim conditions caused by contaminated sensing elements.
Voltage-based and frequency-based MAP sensor diagnostic procedures. Learn to test the 5V reference circuit, measure kPa output against barometric pressure with a scan tool, inspect vacuum lines for leaks, and identify skewed MAP readings that corrupt fuel delivery calculations.
Potentiometer and Hall-effect TPS testing methods using a digital multimeter and oscilloscope. Includes idle and wide-open-throttle voltage specifications, smooth sweep verification, closed-throttle position relearn, and correlation testing against accelerator pedal position sensors.
NTC thermistor testing for engine coolant temperature sensors. Includes resistance-versus-temperature reference charts, two-wire and three-wire ECT circuit analysis, scan tool data validation, and how faulty ECT readings affect cold-start enrichment, idle air control, and radiator fan operation.
Piezoelectric knock sensor diagnostics using an oscilloscope to capture AC voltage waveforms during induced knock events. Covers frequency spectrum analysis in the 5-8 kHz range, piezoelectric crystal integrity testing, false knock detection from mechanical noise, and knock retard monitoring with a scan tool.
Hall-effect and inductive-type camshaft position sensor testing procedures. Learn cam/crank correlation waveform capture, VVT solenoid interaction diagnostics, 5V reference and signal circuit troubleshooting, and how to identify CMP sensor failure patterns in freeze-frame data.
Diagnostic procedures for magnetic inductive (passive) and Hall-effect (active) wheel speed sensors. Covers resistance measurement across the sensor coil, peak-to-peak AC voltage output testing while spinning the wheel, air gap specification verification with a feeler gauge, and oscilloscope pattern interpretation for damaged tone rings.
Systematic approach to diagnosing a failing engine control module. Covers power supply and ground circuit voltage-drop testing, communication bus verification with a scan tool, known-good ECU substitution guidelines, immobilizer relearn procedures, and how to differentiate ECU failures from sensor and wiring faults.
Diagnostic guide for fuel rail pressure sensors and fuel level senders. Covers PWM and analog voltage output FRP sensor testing with a scan tool and oscilloscope, high-pressure fuel system leak-down tests, fuel level sender variable resistance testing through the sweep range, and instrument cluster interpretation of implausible readings.
NTC thermistor-based intake air temperature sensor diagnostic procedures. Includes resistance-versus-temperature lookup tables for common OEM specifications, scan tool ambient air comparison testing, integrated MAF/IAT sensor troubleshooting, and the role of IAT data in speed-density and mass-airflow fuel delivery strategies.
Thermocouple-based exhaust gas temperature sensor testing using a scan tool and millivolt measurement at the sensor connector. Covers DPF regeneration temperature monitoring, pre-turbo and post-DPF sensor location identification, open-circuit and short-to-ground fault code analysis, and extreme temperature range verification up to 900 degrees Celsius.
Dual potentiometer accelerator pedal position sensor testing with a multimeter and oscilloscope. Covers redundant signal comparison between APP1 and APP2 channels, five-wire circuit pinout verification, closed-pedal and wide-open-pedal voltage specifications, signal correlation faults, and throttle actuator control interaction diagnostics.
Testing procedures for reed switch and Hall-effect vehicle speed sensors. Covers AC voltage generation testing by rotating the driven wheel, transmission output shaft speed sensor waveform capture, speedometer circuit continuity verification, and how VSS failure affects shift scheduling, cruise control, and odometer operation.
Complete CAN bus diagnostic strategy covering CAN-H and CAN-L voltage differential measurement with an oscilloscope, 60-ohm termination resistance testing at the DLC, individual node isolation through bus topology analysis, U-code fault interpretation from scan tool data, and identifying short-to-ground or short-to-voltage bus faults.
Diagnostic procedures for NOx sensors in SCR aftertreatment systems and particulate matter sensors in DPF applications. Covers CAN-integrated NOx sensor data validation, lambda-based NOx conversion efficiency assessment, PM sensor regeneration and soot loading PID monitoring, and DEF quality and dosing system interaction verification.
Systematic visual inspection of automotive wiring harnesses: identify chafing, thermal damage, connector corrosion, and rodent damage on wiring insulation.
Locate short circuits with voltage drop testing across fuses, current draw measurement, and circuit breaker cycling to isolate parasitic drains and dead shorts.
Diagnose ground-side faults with voltage drop measurements under load, ground strap continuity checks, and vehicle-specific ground distribution point locations.
Diagnose CAN bus faults with differential voltage measurement, oscilloscope waveform analysis, termination resistor checks, and systematic fault isolation.
Connector repair covering Deutsch, Weather-Pack, and Metri-Pack terminals: pin extraction, proper crimping technique, and weather seal replacement procedures.
Compare soldered vs crimped wire splice repairs: adhesive-lined heat shrink selection, environmental sealing methods, and OEM repair standard compliance.
Find intermittent faults with systematic wiggle testing, thermal camera hot-spot detection, and data logging to capture elusive voltage drops and open circuits.
Diagnose LIN bus single-wire faults and MOST bus fiber optic ring breaks using oscilloscope signal analysis and optical power measurement techniques.
Diagnose fuse boxes with voltage drop testing across fuses, thermal inspection for hot spots, relay socket terminal checks, and corrosion resistance detection.
Test trailer wiring: 7-pin and 4-pin connector pinout checks, ground loop isolation, brake controller signal testing, and lighting circuit troubleshooting.
Identify heat-damaged engine harnesses near exhaust manifolds, EGR tubes, and turbochargers with heat shield inspection and protective looming guidance.
Diagnose FlexRay bus sync faults and automotive Ethernet 100BASE-T1 link drops using eye diagram analysis, time-sync checks, and signal integrity measurements.
Complete diagnostic guide to headlight bulb failure across halogen, LED, and HID (Xenon) technologies. Covers bulb resistance testing, ballast output voltage measurement, igniter diagnosis, D1S/D2S/D3S bulb identification, and CAN bus feedback interpretation.
Technical guide to converting halogen headlights to LED. Covers CAN bus error resolution with load resistors and decoders, beam pattern adjustment for LED emitters, heat dissipation requirements, fan vs passive cooling, and country-specific legal compliance for on-road use.
Systematic diagnosis of turn signal hyperflash conditions. Covers thermal and electronic flasher relay testing, LED-induced hyperflash causes and circuit resistance calculations, load resistor sizing (6 ohm vs 3 ohm), flasher module pinout testing, and BCM-controlled turn signal diagnosis.
Comprehensive electrical diagnosis of power window systems. Covers master switch and individual switch continuity testing, window motor current draw measurement with an inductive amp clamp, regulator electrical fault isolation, pinch protection sensor diagnosis, and LIN bus window module communication testing.
In-depth electrical diagnosis of central locking systems. Covers door lock actuator motor testing (2-wire and 5-wire types), key fob signal verification using RF scanners, BCM integration and CAN bus lock/unlock command diagnosis, door latch microswitch testing, and key fob programming procedures for major brands.
Complete electrical diagnosis of tail light and brake light circuits. Covers bulb socket corrosion inspection and resistance measurement, brake light switch adjustment and continuity testing (2-wire and 4-wire types), trailer light converter module diagnosis, ground circuit voltage drop testing, and dual-filament bulb diagnosis.
Technical diagnosis of daytime running light systems. Covers DRL module input/output testing, automatic headlight sensor diagnosis using scan tool data PIDs, ambient light sensor (photocell) resistance measurement across lux ranges, DRL relay testing, and DRL deactivation switch circuit diagnosis for markets with mandatory DRL requirements.
Comprehensive diagnosis of power mirror electrical systems. Covers mirror positioning motor testing (2-motor 3-wire configuration), heating element resistance and current draw measurement, electrochromic auto-dimming mirror voltage testing, memory mirror module LIN bus diagnosis, and power folding mirror limit switch testing.
Complete diagnosis of horn electrical circuits. Covers horn relay bench and in-circuit testing, clock spring (spiral cable) continuity testing across steering wheel rotation, horn switch contact resistance measurement, horn unit current draw testing, and dual-tone horn frequency verification using an oscilloscope or frequency counter.
Electrical diagnosis of windshield wiper systems. Covers wiper motor park switch continuity testing across wiper positions, rain sensor diagnosis using oscilloscope to verify infrared emitter/receiver function, wiper control module LIN bus communication testing, intermittent mode timer relay diagnosis, and wiper stalk switch resistance ladder testing.
In-depth comparison of Fluke 88V, Brymen BM869s, and Klein MM700 multimeters for automotive use. Covers True RMS accuracy, CAT III/IV safety ratings, and must-have features like RPM measurement, dwell angle, pulse width, and temperature probe capabilities.
Practical oscilloscope setup guide for PicoScope 4425A and Hantek 1008C. Covers voltage scale and time base configuration, edge and pulse-width trigger settings, and interpretation of key waveforms — fuel injector pintle hump, crankshaft sensor, and CAN bus high/low signals.
Comprehensive OBD2 scan tool comparison across five tiers. Launch CRP919X and Autel MK808 provide bidirectional control; BlueDriver offers mobile convenience; Foxwell NT710 and Topdon ArtiDiag500 cover coding functions. Covers protocol support, live data graphing, and manufacturer-specific PIDs.
Master low-amp and high-amp current probe techniques. Covers Fluke i1010 AC/DC current clamp and Pico TA018 low-amp probe for parasitic draw measurement, starter current profiling with 600A clamps, and the differences between inductive (AC-only) and Hall-effect (AC/DC) clamp designs.
Practical guide to using pressure transducers for engine diagnostics. Covers Pico WPS500X in-cylinder pressure waveform capture, fuel rail pressure transducer measurements, exhaust back pressure testing for restricted catalysts, and cranking compression relative testing without removing spark plugs.
How to use FLIR E8 and Seek ShotPro thermal cameras for electrical fault finding. Identify hot spots in fuse boxes revealing high-resistance connections, scan wiring harnesses for overloaded circuits, detect parasitic draw components by temperature signature, and locate failing relays and modules.
Detailed comparison of professional battery testers. Midtronics MDX-650P provides advanced conductance profiling with temperature compensation; Foxwell BT-705 and Topdon BT200 offer affordable conductance testing. Covers load testing vs conductance testing accuracy and battery registration capabilities for modern vehicles.
Master automotive wiring diagram reading across manufacturers. Covers DIN 72552 terminal designations vs SAE J1128 symbols, German (DIN 47002), Japanese (JIS C 3406), and American (SAE J1128) wire color codes, connector pin numbering conventions, and tracing circuits through multi-page schematics.
Professional connector testing techniques using breakout boxes and back-probing methods. Covers Waekon breakout box selection, Fluke and Pomona back-probe pin selection, safe connector insertion without terminal spreading, test lead best practices, and avoiding ECM connector damage during powered circuit testing.
Complete guide to bidirectional scan tool functions. Covers fuel pump activation, VVT solenoid testing, cooling fan command, and throttle body relearn procedures using VCDS (VW/Audi), Toyota Techstream, BMW INPA/ISTA, and Ford FORScan. Includes DPF regeneration and electronic parking brake service modes.
Using automotive smoke machines for leak detection. Covers the Autool SDT-106 professional EVAP smoke tester, Redline Detection Smoke Pro total-tech operations, and building a DIY smoke machine with a paint can, air regulator, and baby oil. Includes EVAP system leak size classification and smoke test safety procedures.
Complete Power Probe usage guide covering the Power Probe IV and PP3 series. Covers short-to-ground and short-to-voltage circuit tracing, component activation with built-in voltage supply, relay bench testing, fuse box testing with Power Probe, and safe current-limited power application to verify circuit integrity.
Essential J2534 device comparison and ECU programming guide. Covers DrewTech CarDAQ Plus 3, Opus MongoosePro ISO/CAN, and VXDIAG VCX Nano for OEM software access. Details Toyota TIS, GM SPS2, Ford FJDS/FDRS, and VW ODIS flashing procedures, battery voltage requirements, and brick prevention best practices.
Noise, vibration, and harshness diagnostic tool guide. Covers Pico Diagnostics NVH kit with accelerometer-based vibration analysis, Steelman 06600 ChassisEar wireless noise detection for pinpointing drivetrain and suspension noise sources, and electronic stethoscopes for isolating electrical noise from alternators, relays, and fuel injectors.
Comprehensive HV safety guide for hybrid/EV technicians covering Class 0 insulated glove requirements per ASTM D120, manufacturer-specific de-energizing procedures for Toyota, Honda, and Ford, CAT III 1000V meter selection, and lockout/tagout protocols per NFPA 70E.
In-depth guide to diagnosing Toyota Prius NiMH HV battery packs across Generations 2, 3, and 4. Covers Dr. Prius app live data analysis, block voltage deviation testing (max 0.3V delta threshold), internal resistance measurement, and evaluating reconditioning vs. replacement decisions using Toyota Techstream and aftermarket balancing tools.
Step-by-step guide to replacing individual cells in hybrid battery packs. Covers bus bar cleaning with contact cleaner and brass brush, torque specification for M6 bus bar nuts (5.4 Nm on Toyota), cell balancing to within 0.05V, and proper thermal management paste application using OEM-spec compounds.
Technical guide to diagnosing EV charging systems across all levels. Covers SAE J1772 proximity and pilot signal testing, Level 2 onboard charger fault codes, DC fast charge CCS (ISO 15118) and CHAdeMO communication protocol analysis, charge port temperature sensor diagnostics, and AC input voltage verification at the onboard charger module.
Comprehensive diagnosis of regenerative braking electrical components. Covers brake pedal position sensor voltage output curves and calibration, motor-generator (MG2 in Toyota hybrids) operation verification using scan tool torque data, ABS actuator communication diagnosis, and troubleshooting regen engagement faults using bidirectional scan tool controls.
Complete guide to diagnosing Toyota Hybrid System (THS) warning lights and DTCs. Covers Dr. Prius and Techstream code reading for P0A80 (battery degradation), P3000 (battery control system), P0A7F (battery cell deterioration), and P0A93 (inverter coolant pump performance). Includes inverter coolant pump activation tests and flow rate checks.
Technical guide to testing hybrid vehicle DC-DC converters that step down HV traction battery voltage (200-400V) to 12V auxiliary. Covers output voltage verification (13.5-14.5V target), Toyota Prius converter under driver seat access, Honda Insight IPU converter testing, Ford Escape hybrid converter specs, and diagnosing 12V battery drain caused by converter failure.
Detailed diagnosis of EV/HV contactors (main relays), precharge circuits, and safety interlocks. Covers contactor coil resistance and voltage drop testing, precharge resistor value verification (typically 30-50 ohms) and timing, isolation resistance measurement using a megohmmeter at 500V DC (>1 MOhm/V threshold), and HVIL circuit continuity diagnostics across all interlock connectors.
Comprehensive electric drive motor (MG1/MG2) diagnostic guide. Covers three-phase winding resistance measurement (milliohm range, using 4-wire Kelvin method), insulation resistance testing between phases and to ground, resolver/exciter coil diagnosis for rotor position sensing, motor temperature sensor (thermistor) testing, and mechanical inspection for demagnetization and bearing noise.
Technical guide to hybrid inverter/converter assembly diagnosis. Covers IGBT power module testing using diode-check mode, DC bus capacitor discharge verification (target <60V within 5 minutes, Toyota spec), inverter cooling system flow testing, and using Techstream active test to verify MG1 and MG2 inverter operation through commanded torque output.
Comprehensive guide to diagnosing EV/hybrid battery range loss and State of Health (SOH). Covers Leaf Spy Pro and Tesla diagnostic tool data analysis, capacity testing through controlled discharge cycles, cell voltage imbalance detection patterns, factors affecting lithium-ion degradation (temperature, SOC cycling, calendar aging), and interpreting battery parameter identification (BPI) data.
Specialized guide to diagnosing electrically driven AC compressors in hybrid and EV vehicles. Covers Toyota/Lexus ES18 and ES27 electric compressor isolation resistance testing (>1 MOhm at 500V), compressor inverter module communication diagnosis, HV input voltage verification, A/C ECU DTC analysis including P0AA6 (leak detected), and common compressor inverter internal short circuit failure patterns.
Diagnose frequent Toyota electrical faults across Corolla, Camry, RAV4, and Hilux models. Covers alternator overcharge failures, ETSC (Electronic Throttle Smart Control) limp-mode triggers, immobilizer key sync issues, and Techstream scan tool diagnostic procedures for DTCs and active tests.
Systematic diagnosis of Honda electrical issues on Civic, Accord, CR-V, and Pilot platforms. Covers ELD (Electronic Load Detector) charging strategy faults, PGM-FI main relay solder joint failures, VTEC solenoid electrical circuit testing with oscilloscope, and HDS (Honda Diagnostic System) bidirectional controls.
Professional-level BMW electrical diagnosis covering 3-Series (E90/F30), 5-Series (E60/G30), and X5 models. Diagnose CAS (Car Access System) module communication failures, FRM (Footwell Module) corrupted EEPROM recovery, power management IBS sensor faults, and how to use ISTA+ for guided troubleshooting and test plans.
Diagnose widespread Ford electrical faults on F-150, Focus, Escape, and Transit vehicles. Covers Smart Junction Box (SJB) water ingress corrosion patterns, GEM (Generic Electronic Module) relay driver failures, PATS (Passive Anti-Theft System) key programming procedures, and FORScan software for module-level diagnostics and configuration.
Comprehensive Mercedes-Benz electrical system diagnosis for C-Class (W204/W205), E-Class (W212/W213), and S-Class models. Diagnose SAM (Signal Acquisition Module) communication failures, CAN-B bus wake-up/sleep issues, battery control module faults, and XENTRY/DAS guided troubleshooting with actual values and actuations.
Diagnose common VAG (Volkswagen Audi Group) electrical faults across Golf, Passat, A4, and A6 platforms. Covers VCDS (VAG-COM) long coding and adaptation channel procedures, comfort control module (J393) water ingress diagnosis, driver door wiring harness flex-break detection, and ignition coil primary circuit DTC tracing.
Diagnose Hyundai and Kia shared-platform electrical faults on Elantra, Sonata, Sportage, and Tucson models. Covers EPS (Electric Power Steering) MDPS motor torque sensor calibration, smart key SMK module registration via GDS, brake pedal switch signal plausibility faults, and engine ground strap voltage drop testing.
Diagnose GM electrical system faults on Silverado, Equinox, Malibu, and Tahoe platforms. Covers BCM (Body Control Module) ground reference integrity checks, PassLock VATS security relearn procedures, GDS2 scan tool data bus health monitoring, and common chassis ground point G101/G102 corrosion inspection and remediation.
Diagnose Nissan electrical faults on Altima, Rogue, Pathfinder, and Sentra models. Covers IPDM (Intelligent Power Distribution Module) internal relay failure diagnosis, NATS (Nissan Anti-Theft System) key synchronization procedures, Consult-III plus active test functions, and alternator smart charge LIN bus communication verification.
Diagnose Stellantis multi-brand electrical faults on Jeep, RAM, Dodge, Chrysler, Peugeot, and Citroen vehicles. Covers TIPM (Totally Integrated Power Module) relay bypass procedures, CAN-C and CAN-IHS bus topology analysis, wiTECH diagnostic system gateway module access, and common engine-to-chassis ground strap resistance verification.