MON–FRI 7AM–5PM · SAT 7AM–2PM·4.9★ 350+ GOOGLE REVIEWS·3 MIN OFF I-94 · RIGHT BY US-41 (SKOKIE HWY)·MOBILE ROADSIDE SERVICE AVAILABLE·
Diesel mechanic running computer diagnostics on a semi truck engine at night at RT Group

Engine Repair & Diagnostics

RT Group repairs diesel engines and runs full ECM/computer diagnostics in Zion, IL — check-engine-light triage and common failure-point repair for major diesel platforms. Call (224) 588-3442.

Diesel Engine Repair

From performance loss to full rebuilds, our techs work on major diesel engine platforms used across Class 6-8 trucks. We diagnose before we quote, so you know the actual cause before any work starts.

ECM / Computer Diagnostics

Modern diesel engines run through an engine control module (ECM) that logs fault codes long before a problem becomes a breakdown. We pull and interpret those codes to triage check-engine lights fast and accurately.

Common Failure Points We See

  • Fuel system and injector issues
  • Turbocharger and boost-related faults
  • After-treatment system faults (DPF, SCR, EGR)
  • Sensor failures triggering false or misleading codes
  • Cooling system leaks and overheating

If your fault ties into a broader after-treatment or electrical issue, see also our Semi Truck Repair page.

Why RT Group

Built for Drivers Who Can't Afford Downtime

Diagnose before we quote

Fault codes get interpreted, not just cleared — you get the real cause.

Major diesel platform coverage

Techs experienced across the diesel engines common to Class 6-8 trucks.

Check-engine-light triage

Fast turnaround on figuring out if it's urgent or can wait.

Same-property fix

Diagnostics and repair happen in the same bay — no handoff delay.

Reviews

4.9★ from 350+ Google Reviews

★★★★★

“Blew an air line on I-94, they got the mobile unit out and had me rolling the same day. No upselling, no games, just fixed it right.”

[FIRST NAME]Owner-Operator, Kenosha WI
★★★★★

“Cleanest heavy-duty shop I’ve been to in the area. They diagnosed my transmission issue, quoted it straight, and had it done when they said they would.”

[FIRST NAME]Fleet Owner, Waukegan IL
★★★★★

“We bring all our DOT inspections here. In and out fast, paperwork done right, and they actually answer the phone.”

[FIRST NAME]Safety Manager, Lake County IL
Read All Reviews →
FAQ

Common Questions

My check engine light is on — is it safe to keep driving?
It depends on the code. Call us and we can help you triage whether it's safe to continue or needs immediate attention.
Can you clear a fault code without a real repair?
We diagnose and fix the underlying cause — clearing a code without addressing the fault usually means it comes right back.
Do you work on all major diesel engine brands?
Yes, our techs are experienced across the diesel platforms most common in Class 6-8 trucks.

Ready When You Are

Call now to talk to a live person, or request a quote and we'll follow up fast.

Call Now: (224) 588-3442