1985 Autocar: we work on any truck
If it runs diesel and needs help, we'll show up. Age is not a barrier: classic, vintage, or modern.
Mobile Kenworth Repair
Kenworth Truck Repair in Charleston, SC. We Come to You.
On-site diagnostics and repair for Kenworth T680, T880, W900 and W990 trucks, plus the T180 through T480 medium-duty line. Whether it runs a PACCAR MX-13, an MX-11 or a Cummins X15, we test the aftertreatment, coolant, transmission, air or electrical fault where the truck is parked and tell you what failed before any parts get ordered.
- PACCAR MX-13/MX-11 and Cummins X15 derate, aftertreatment and coolant-loss faults
- TX-12 shifting, air system and multiplex electrical diagnostics
- Charleston, North Charleston, Summerville, Goose Creek, Mount Pleasant
What We Handle On-Site
Kenworth problems we diagnose and repair
MX-13 and MX-11 aftertreatment
PACCAR MX engines pair EGR with a DOC, DPF and an SCR system dosed with DEF. We run down NOx sensor codes, clogged or crystallized DEF dosers, and regen problems tied to the pressure sensors, checking wiring and exhaust leaks before condemning a sensor.
Coolant loss with no puddle
An internal crack in the EGR cooler can drain coolant slowly with nothing on the ground and only intermittent codes. We pressure test the cooling system and watch the exhaust and overflow tank to separate an EGR cooler from a hose, water pump or head gasket problem.
Cummins X15 boost and exhaust brake
Plenty of T680, T880 and W990 trucks carry the X15. Low boost, a weak exhaust brake and a derate often point to a worn or sticking VGT actuator. We read the actuator data and test it before anyone orders a turbo.
TX-12, air and multiplex electrical
The PACCAR TX-12 automated manual depends on a healthy air supply and a clutch that stays in range. We hunt air leaks, check the air dryer, read transmission faults, and trace multiplex problems through the cab controller (CECU) and J1939 network.
Kenworths in the Lowcountry
From T680 sleepers to T880 dump trucks
Kenworths generally work two kinds of jobs. T680 and W990 tractors run regional and long-haul freight, while the T880 is built for vocational work like dump, mixer, refuse, heavy haul, tanker and tow. A lot of W900 and T800 trucks are still earning a living too, even though Kenworth is ending W900, T800W and C500 production in 2026 and naming the W990 and T880 as their successors.
Powertrains vary more than people expect. A T680 or T880 can carry a PACCAR PX-9, MX-11, MX-13 or Cummins X15, behind a PACCAR TX-12 or TX-18, an Eaton Endurant, or on the T880 an Allison automatic. The medium-duty T180 through T480 run PACCAR PX-7 and PX-9 engines, which Cummins builds on its B6.7 and L9, with the PACCAR TX-8 automatic as standard. Knowing which combination is in front of us decides which tests come first.
We are an independent mobile shop, not a Kenworth dealer. We bring diagnostic equipment to the truck and work the fault from codes and live data. Open recalls, like those on some 2023 T680s for a freezing digital dash and the steering gear, still go through a dealer, so check the VIN on NHTSA's recall lookup.
Why operators call us
- Mobile service where the truck is sitting
- Testing before parts replacement
- Clear written findings and next steps
- Commercial diesel and fleet-focused support
- 24/7 Charleston-area availability
How We Work
From your first text to a fixed Kenworth
1. Text the truck details
Model (T680, T880, W900, W990 or medium duty), engine (MX-13, MX-11, X15 or PX-9), the year or VIN, and exactly where it is parked.
2. Send the dash and the codes
A photo of the dash, the active fault codes, and whether the truck is derated or held to 5 mph tell us which tests and tools to bring.
3. Tell us what changed
Coolant you keep topping off, a regen that never finishes, hard shifts, a recent repair. That history often narrows the problem faster than codes.
4. We test at the truck
Depending on the complaint: aftertreatment temperatures and pressures, DEF dosing, NOx readings, boost and VGT position, cooling system pressure, or air pressure and leaks.
5. Fix the cause, not the light
We repair the failed sensor, doser, wiring or leak behind the fault instead of clearing codes and sending the Kenworth out to derate again.
6. Findings you can file
You get what was checked, what failed, what we did and what still needs attention, in plain language for the unit's records.
Need a Kenworth mechanic in the Charleston area?
Call or text Lowcountry Diagnostics, day or night, and we will come to the truck.
Common Kenworth repair questions
Do you work on Kenworths with PACCAR MX-13 and MX-11 engines?
Yes. We diagnose MX-13 and MX-11 Kenworths on-site, including NOx sensor codes, DEF doser and SCR faults, EGR valve and EGR cooler problems, regen trouble and coolant loss.
Can you fix a Kenworth that is derated to 5 mph?
Often, yes. A 5 mph derate on an MX-13 or X15 usually traces back to the DEF or SCR side, such as a clogged or crystallized doser or a failed NOx sensor. We find the cause where the truck sits so it does not derate again after a reset.
Do you work on Cummins X15 powered Kenworths?
Yes. Many T680, T880 and W990 trucks run the Cummins X15. We diagnose VGT actuator faults, low boost, weak exhaust brake complaints, EGR problems and aftertreatment codes on those trucks at your yard, jobsite or roadside.
Do you handle TX-12 transmission and air system problems?
Yes. We read TX-12 fault codes, look into clutch position faults, and test for air leaks and air dryer problems that cause hard shifts.
Are you a Kenworth dealer?
No. Lowcountry Diagnostics is an independent mobile diesel service based in Goose Creek, and we come to your truck across the Charleston area 24/7. Open recall campaigns go through a Kenworth dealer. Call or text (843) 310-0995.
Request Kenworth Repair
Tell us where the Kenworth is and what it is doing. For a truck that is down or derated, calling or texting is fastest.
Truck down or derated? Call or text (843) 310-0995 now.
Recent Repair Photos
A look at the repairs we make
Real field photos from Lowcountry Diagnostics, from engine diagnostics and electrical to hydraulic, HVAC, and heavy-duty truck service, handled on-site across the Charleston area.
Reviews
What Charleston truck owners and fleets say
“Great team, personal and professional. These men were responsive and had great diagnostic equipment paired with experience…”
“These guys really know their stuff. Couldn't recommend em more.”