Modern commercial trucks are as much computer as mechanical. When a check engine light comes on, fault codes appear, a sensor fails, or an electrical component fails entirely — you need a shop with the right diagnostic tools and the experience to interpret what they're telling you. Interstate Fleet Services provides comprehensive electrical diagnostics and repair for all major commercial truck platforms in Rock Hill, SC and the Carolinas.
We don't just read codes and clear them — we find the root cause, fix it, and verify the repair. A fault code is a symptom, not a diagnosis. In 26 years of truck repair, we've learned that misdiagnosed electrical problems waste money and keep coming back.
Call Now: (803) 329-9755We read and interpret engine fault codes on all major platforms. Active faults, stored faults, and freeze frame data all provide information about what happened and when.
DEF quality sensor codes, NOx sensor failures, SCR catalyst faults, and DEF injector codes that cause derating. DEF system diagnostics are among our most common calls.
Wheel speed sensor failures, ABS modulator valve faults, and ABS controller issues on both trucks and trailers. ABS faults are a DOT inspection concern.
Alternator testing, replacement, and charging system diagnostics. A failing alternator drains batteries and can strand a truck. We test and replace on-site in most cases.
Battery load testing, battery replacement, and battery management system diagnostics on modern trucks with battery monitoring. Commercial truck batteries are heavy-duty — we come equipped.
Chafed wiring, moisture-damaged connectors, rodent-damaged harnesses, and heat-damaged wiring repaired at the harness level — not just at the symptom.
Starter motor testing, replacement, solenoid service, and battery cable inspection. A no-start condition diagnoses from the battery terminal to the starter.
7-way connector repairs, trailer wiring harness repair, marker light circuits, brake light circuits, and trailer ABS system service.
HVAC system electrical, power window circuits, lighting systems, and cab electrical repairs that affect driver comfort and safety.
We use professional-grade scan tools capable of reading and clearing codes on all major truck platforms including PACCAR (MX-11, MX-13), Cummins (ISX, X15, ISB), Detroit Diesel (DD13, DD15), Navistar MaxxForce, Volvo D11/D13, and Mack MP8. We read live data, perform active tests, and access platform-specific diagnostic functions.
Yes. Modern commercial trucks are highly electronic, and we have the equipment and training to diagnose both software-related faults and physical wiring failures. We work on trucks from the 1990s with basic electronics to fully modern platforms.
An active fault is a condition currently present that the ECM is actively monitoring. A stored (inactive) code is a fault that occurred in the past but has since cleared. Stored codes are valuable for identifying developing problems before they become breakdowns. We check both and advise on what requires attention.
Possibly. Many check engine lights on modern trucks are for emissions system faults (DEF, DPF, EGR) that don't immediately affect performance but will cause derating if ignored. Get them scanned and assessed — don't assume 'runs fine' means no action needed.
Yes. Trailer wiring harness repairs, lighting faults, ABS sensor replacements on trailers, and 7-way connector repairs are all within our capability. Trailer electrical failures are a major cause of DOT inspection violations.