1997–2006
TJ / LJ
4.0L models
Manual + automatic
Built by Jeep owners • for Jeep owners
The Jeep WranglerDIY Companion
Practical guides, real-world solutions, and easy-to-follow instructions for TJ, LJ, JK, and JKU owners. Learn to diagnose, maintain, and repair your Jeep, save money, and become a more confident and self-reliant owner.
TJ / LJ 4.0L 1997–2006JK / JKU 3.8L 2007–2011JK / JKU 3.6L 2012–2018
Check your Wrangler
Does the Companion cover my Jeep?
Yes, if your Wrangler is one of the generations shown to the right. Coverage includes applicable two- and four-door models with manual and automatic transmissions.
2007–2011
JK / JKU
3.8L engine
Manual + automatic
2012–2018
JK / JKU
3.6L engine
Manual + automatic
The first edition does not cover TJ models with the 2.4L or 2.5L engine, or YJ, JL, or Gladiator models. Always confirm procedures and specifications against factory information for your exact year, engine, transmission, trim, and options.
Who we are
Real Jeeps. Real fixes.Lessons earned the hard way.
I’m Martin Slater, the author behind The Jeep Wrangler DIY Companion and the founder of OMG! Old Men’s Garage & Off-Road Misadventures. My interest in four-wheel drives began in Ecuador and followed me through England and back to the United States.
Over the past fifteen-plus years, our family has maintained, repaired, diagnosed, and modified JKs, JKUs, and TJs together. We have made mistakes, bought parts we did not need, found strange electrical problems, and learned that a careful test is usually worth more than a confident guess.
This Companion is the practical book we wish we had when our first Wrangler arrived in the driveway.
15+ years
of family Jeep ownership and DIY repairs
200K miles
within reach when maintenance becomes a habit
The main build
One Companion. A garage full of answers.
Designed to live beside the factory service manual, not replace it. The Companion focuses on the information owners reach for most often and explains why each check matters.
See inside the manuscript01
Quick-reference answers
Fluid specifications, capacities, torque values, filters, plugs, fuses, relays, and connector locations.
02
Hands-on procedures
Clear steps for maintenance, testing, inspection, and the repairs owners are most likely to tackle.
03
Safety built into the work
Warnings, tool settings, stop points, and the checks that prevent a small job from becoming a large one.
04
Diagnosis before parts
A consistent approach: record the symptoms, start with the basics, test the circuit, and verify the result.
Inside the Companion
- Section 01: Jeep Ownership
- Section 02: Quick Reference
- Section 03: Basic Maintenance & Diagnostics
- Section 04: Recommended Tools & Supplies
- Section 05: Understanding Your Jeep
- Section 06: Dashboard, Gauges & Warning Lights
- Section 07: OBD Diagnostics & Troubleshooting
- Section 08: Common Problems
- Section 09: Practical Information, Solutions & Mods
- Section 10: Jeep Easter Eggs (and Ducks)
- Section 11: Resources
Turn a few pages
See how the Companion works in the garage.
Section 01
Jeep Ownership
Wrangler ownership, capability, traditions, model identification, and the Jeep community.
Section 02
Quick Reference
Garage-side specifications, capacities, service parts, electrical information, and terminology.
Section 03
Basic Maintenance
Maintenance planning, electrical checks, fluids, cooling, brakes, tires, inspections, and cleaning.
Section 04
Recommended Tools & Supplies
Carry kits, safety equipment, hand tools, power tools, specialty tools, and garage supplies.
Section 05
Understanding Your Jeep
A system-by-system explanation of how power, fluids, electricity, and information move through a Wrangler.
Section 06
Dashboard, Gauges & Warning Lights
What the gauges, lamps, displays, and chimes mean—and what the driver should do next.
Section 07
OBD Diagnostics & Troubleshooting
A test-first approach to trouble codes, scan data, electrical checks, and finding the actual cause.
Section 08
Common Wrangler Problems
Recurring Wrangler symptoms, likely causes, practical checks, and repair confirmation.
Section 10
Jeep Easter Eggs (and Ducks)
The hidden details, playful traditions, and community customs that add personality to Jeep ownership.
Section 11
Jeep Wrangler Resources
Factory information, repair references, trusted suppliers, communities, and additional help.
Free from the workbench
Useful pages for the glovebox and garage wall.
Download a maintenance log, a pre-trip Jeep inspection checklist, and a diagnostic worksheet. Print them, write on them, and keep better notes about what your Jeep is telling you.
Get the free downloads- 01Jeep Maintenance Log
- 02Pre-Trip Jeep Inspection
- 03Jeep Diagnostic Worksheet
A subscriber benefit
Stuck on a Jeep problem? Ask the garage.
Tell us what your Wrangler is doing, which codes you found, and what you have already tested. We will help you organize the next diagnostic steps and avoid the parts cannon whenever possible.
Submit a Jeep question