John Deere 5620, 5720 and 5820 Tractors Diagnosis and Tests Manual (TM4791)

What's Covered in This Manual

This is the Diagnosis and Tests service manual (TM4791) for the John Deere 5620, 5720 and 5820 tractors, in both 2WD and MFWD (mechanical front-wheel drive) configurations. These tractors use the PowrQuad or PowrQuad Plus transmission, and a good chunk of this manual is built around the electronic control units that run it - the manual dedicates an entire section to the BCU (Basic Control Unit), BIF (Basic Informator), EPC (control unit for the PowrQuad Plus transmission) and PRF (Performance Monitor), plus the data bus system that ties them together.

One detail worth knowing before you start a wiring diagnosis: the electrical system section splits its wiring harness listings at serial number 424816, so earlier and later tractors in this line use different harness diagrams. Check your tractor's own serial plate and use the matching set rather than assuming the first one you find applies.

Beyond the electronics, the manual covers everything else a technician needs to isolate a fault on these tractors: engine operational checks and adjustments, the fuel/air intake/cooling system, electrical circuit checks and functional schematics, the PowrQuad and PowrQuad Plus transmissions themselves, drive systems, steering and brakes, the hydraulic system, and the operator's cab, closing with a special tools reference. It's written as a diagnostic companion rather than a parts-replacement guide - test values and diagnostic trees are the focus throughout, so you can confirm exactly what's wrong before you start pulling anything apart.

Table of Contents

• Section 210 - General Information - safety measures, general references
• Section 220 - Engine - operational checks, tests and adjustments
• Section 230 - Fuel, Air Intake and Cooling Systems - tests, adjustments, theory of operation
• Section 240 - Electrical System - circuit checks, component testing, wiring harnesses (serial break at 424816)
• Section 245 - Electronic Control Units - BCU, BIF, EPC and PRF diagnostics, data bus theory
• Section 255 - PowrQuad and PowrQuad Plus Transmissions - transmission diagnosis
• Section 256 - Drive Systems - driveline diagnosis
• Section 260 - Steering and Brakes - diagnosis and tests
• Section 270 - Hydraulic System - diagnosis and tests
• Section 280/290 - Miscellaneous, Operator's Cab - cab systems
• Section 299 - Special Tools - diagnostic tool reference