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 Peterbilt Repair
Peterbilt Truck Repair in Charleston, SC. We Come to You.
On-site diagnostics and repair for Peterbilt 579, 589, 389 and 567 trucks, plus medium-duty models. We come to your yard, jobsite, or roadside spot, read the PACCAR or Cummins fault codes, test for the cause, and tell you what failed before any parts get ordered.
- PACCAR MX-13, MX-11 and Cummins X15 derates, EGR, and aftertreatment faults
- TX-12 shifting, air system, multiplex electrical, and no-start problems
- Charleston, North Charleston, Summerville, Goose Creek, Mount Pleasant
What We Handle On-Site
Peterbilt problems we diagnose and repair
MX-13 and MX-11 derates
PACCAR MX engines pair EGR with a DOC, DPF, and SCR system that doses DEF. A NOx sensor fault or a sticking, crystallized DEF doser can pull power in steps until the truck is held to 5 mph. We check wiring, exhaust leaks, and doser output before condemning a sensor.
Cummins X15 in a 579, 567, or 589
The X15 runs a variable geometry turbo and a single-module DPF and SCR unit. A worn or seized VGT actuator shows up as low boost, a derate, and a weak engine brake. We compare actuator position to what the ECM commands and test the doser and NOx sensors.
Coolant loss with no leak
An EGR cooler that cracks inside pushes coolant into the exhaust, so there is no puddle, just a dropping level and scattered codes. On MX engines coolant also heats the DEF tank, so a cooling fault can surface as a DEF problem. We pressure test and trace it on-site.
TX-12 shifting and CECU faults
The TX-12 is a 12-speed automated manual PACCAR builds with Eaton. Fault 706 (clutch position), hard shifts, and failed clutch learns can come from air supply, the clutch actuator, or clutch wear, so we check air pressure and the dryer first. Dead gauges and network codes get traced through the CECU behind the center console and its J1939 wiring.
Know Your Peterbilt
Models and powertrains we work on
The 579 is Peterbilt's on-highway truck, offered with the PACCAR MX-13, MX-11, or Cummins X15. The 589 replaced the 389, which Peterbilt built through the end of 2023, and it comes with the MX-13 or X15 behind an Eaton manual, a TX-12 or Endurant, or an Allison automatic.
On the vocational side, the 567 handles dump, roll-off, and transfer work with the MX-13, MX-11, PX-9, or X15, and the TX-12 PRO is aimed at dump, tanker, and municipal duty. The low-cab-forward 520 is a refuse truck, now offered with the MX-11.
The medium-duty 535, 536, 537 and 548 run the PACCAR PX-7 (6.7L) or PX-9 (8.9L), both built by Cummins, with the PACCAR TX-8 automatic, and the 537 also offers Allison and Eaton transmissions. We work on those and on older 337, 348 and 220 trucks the same way: we read the engine and transmission codes and test the same aftertreatment, cooling, air and electrical items we check on the Class 8 trucks, at your yard or jobsite.
Between them, these models cover regional and long-haul freight, dump and construction work, and roll-off and refuse routes. Since 2010 every PACCAR MX engine has carried EGR plus a DOC, DPF, and SCR with DEF, and since 2017 the X15 has used the Cummins single-module system.
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
What to send us and what happens next
1. Text the model, engine, and codes
Send the model (579, 589, 567, 520, or medium duty), the engine (MX-13, MX-11, X15, or PX-9), the year, and a photo of the dash or the active fault codes.
2. Tell us what it is doing
Derate, low power, coolant dropping, white smoke, shifting trouble, dead gauges, or a no-start. Note whether it happens hot, cold, loaded, or at idle.
3. We come to the Peterbilt
Yard, jobsite, terminal, or roadside across the Charleston area, day or night.
4. Codes, live data, and tests
We read the engine and aftertreatment modules, then test NOx readings, DEF dosing, MAP, exhaust and DPF differential pressure, VGT position, air pressure and network voltage.
5. Fix the cause, not the light
We repair the failed sensor, doser, wiring, or component instead of clearing codes and sending it back out.
6. Plain written findings
You get what was tested, what failed, and the next step. On a 2022 or 2023 579 with a frozen digital dash or a steering concern, we will also point you to the open recalls.
Need a Peterbilt mechanic in the Charleston area?
Call or text Lowcountry Diagnostics with the model, engine, and codes, and we will come to the truck.
Common Peterbilt repair questions
Do you work on Peterbilts with PACCAR MX-13 or MX-11 power?
Yes. We diagnose and repair Peterbilts with PACCAR MX-13 and MX-11 engines, including NOx sensor faults, DEF doser problems, EGR valve and cooler issues, and DPF regen derates. We check wiring and exhaust leaks before replacing a sensor.
Can you fix a Peterbilt with a Cummins X15?
Yes. The X15 is offered in the 579, 567 and 589. We handle VGT actuator faults, EGR restriction, SCR NOx sensor codes and DEF doser problems on-site.
Do you work on the TX-12 automated transmission?
Yes. We diagnose TX-12 and Endurant shift complaints, clutch position faults and failed clutch learns. We start with air supply and the air dryer, because a weak air system can show up as a shifting problem.
Do you work on medium-duty Peterbilts?
Yes. We work on the 535, 536, 537 and 548 with PACCAR PX-7 and PX-9 engines, plus older 337, 348 and 220 trucks, at your yard or jobsite.
Request Peterbilt Repair
Tell us where the Peterbilt is, the model and engine, and what it is doing. For a truck-down or derate call, calling or texting is fastest.
Peterbilt down or in derate? 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.”