Part of the John Deere Repair Manuals.
This is the Operation and Test technical manual for John Deere 8120T, 8220T, 8320T, 8420T and 8520T track tractors (). It is the diagnostic half of the factory library: service codes, observable symptoms, system diagnosis, and the actual test specs a tech needs at the connector. You get the seven-step electrical test procedure, full wiring schematics, powershift transmission checks, hydraulic operational tests with theory of operation, and the ACU address tables with real voltage windows - hand throttle 0.50-2.50 volts full back, SCV lever positions, shift lever bit codes. AMS coverage includes GreenStar, AutoTrac and JDLink diagnostics. These tractors talk through their controllers; this book is how you listen. Pair it with TM1971 when it is time to pull things apart.
What's Inside This Manual
| System | Pages | Key Topics |
|---|---|---|
| General | 8-85 | Safety Procedures, General References, Bolt and Cap Screw Torque Values, Glossary of Terms, JIC Hydraulic Symbols |
| Service Codes | 86-680 | PCU Code Diagnostics, CCU Code Diagnostics, ACU Code Diagnostics, SCU Code Diagnostics, SSU Code Diagnostics, ATC Code Diagnostics |
| Observable Symptoms | 681-840 | Electrical Symptoms, Operator Station Symptoms, Steering Symptoms, Hitch Symptoms, Heating Ventilation and Air Conditioning Symptoms |
| System Diagnosis | 841-909 | Steering and Brakes System, Transmission System, Hydraulic System, Climatrak |
| Engine | 910-931 | Operational Checks, Tests and Adjustments, Theory of Operation, Schematics and Diagrams |
| Fuel and Air | 932-945 | Fuel System Theory of Operation, Air Intake Theory of Operation |
| Electrical | 946-1121 | Wiring Diagrams and Schematics, Electrical Schematic Symbols, Circuit Types and Malfunctions, Seven-Step Electrical Test Procedure, Using a Probe Light and Digital Multimeter |
| Control Units | 1122-1714 | CCU References, PCU References, ACU References, SCU References, SSU References, HCU References, Codes and Addresses |
| Transmission | 2084-2208 | Powershift Transmission, Operational Checks, Tests and Adjustments, Theory of Operation |
| Drive Systems | 2209-2226 | Theory of Operation, Tests and Adjustments |
| Steering and Brakes | 2227-2284 | Preliminary Checks, Operational Checks, Theory of Operation, Schematics and Diagrams, Tests and Adjustments |
| Hydraulics | 2285-2412 | Preliminary Checks, Operational Checks, Hydraulic Theory of Operation, Pressure and Flow Tests, Selective Control Valve Tests |
| Operator Station | 2413-2580 | Preliminary Checks, Operational Checks, Theory of Operation, Tests and Adjustments |
| Tools | 2581-2607 | Fabricated Tools, Test Kits |
| Ag Management Solutions (AMS) | 1715-2083 | GreenStar Diagnostics, JDLink Diagnostics, AutoTrac Diagnostics, Field DOC Operation and Tests, GPS Position and StarFire Receiver Tests |
Quick Reference Specifications
| Specification | Value | Page |
|---|---|---|
| ACU Address 03 | ||
| Hand Throttle Voltage (Full Back) | 0.50-2.50 Volts (ACU Address 03) | p. 86 |
| Hand Throttle Voltage (Full Forward) | 2.50-4.50 Volts (ACU Address 03) | p. 86 |
| Hand Throttle Voltage Range (Prior to Software Version 30) | >1.78 Volts (ACU Address 03) | p. 86 |
| Hand Throttle Voltage Range (Software Version 30 and Above) | >1.58 Volts (ACU Address 03) | p. 86 |
| ACU Address 08 | ||
| Rear Hitch Load / Depth Control Voltage (CCW) | 0.50-2.50 Volts (ACU Address 08) | p. 86 |
| Rear Hitch Load / Depth Control Voltage (CW) | 2.50-4.50 Volts (ACU Address 08) | p. 86 |
| Rear Hitch Load / Depth Control Voltage Range (Prior to Software Version 30) | >1.78 Volts (ACU Address 08) | p. 86 |
| Rear Hitch Load / Depth Control Voltage Range (Software Version 30 and Above) | >1.58 Volts (ACU Address 08) | p. 86 |
| ACU Address 09 | ||
| Rear Hitch Lever Control Voltage (Raise) | 0.50-2.50 Volts (ACU Address 09) | p. 86 |
| Rear Hitch Lever Control Voltage (Lower) | 2.50-4.50 Volts (ACU Address 09) | p. 86 |
| Rear Hitch Lever Control Voltage Range (Prior to Software Version 30) | >1.78 Volts (ACU Address 09) | p. 86 |
| Rear Hitch Lever Control Voltage Range (Software Version 30 and Above) | >1.58 Volts (ACU Address 09) | p. 86 |
| ACU Address 10 | ||
| Rear Hitch Raise Limit Control Voltage (Limited Raise) | 0.50-2.50 Volts (ACU Address 10) | p. 86 |
| Rear Hitch Raise Limit Control Voltage (Maximum Raise) | 2.500-4.50 Volts (ACU Address 10) | p. 86 |
| Rear Hitch Raise Limit Control Voltage Range (Prior to Software Version 30) | >1.78 Volts (ACU Address 10) | p. 86 |
| Rear Hitch Raise Limit Control Voltage Range (Software Version 30 and Above) | >1.58 Volts (ACU Address 10) | p. 86 |
| ACU Address 11 | ||
| Rear Hitch Rate-of-Drop Control Voltage Range (Prior to Software Version 30) | >1.78 Volts (ACU Address 11) | p. 86 |
| Rear Hitch Rate-of-Drop Control Voltage Range (Software Version 30 and Above) | >1.58 Volts (ACU Address 11) | p. 86 |
| All Models | ||
| SCV Control Voltage and Switch Status (Float) | 0.2.0-1.2.0 (ACU Address 12); 0.2.0-1.2.0 (ACU Address 13); 0.2.0-1.2.0 (ACU Address 14); 0.2.0-1.2.0 (ACU Address 15); 0.2.0-1.2.0 (ACU Address 16) | p. 86 |
| SCV Control Voltage and Switch Status (Retract / Forward Detent) | 1.2.1-1.8.1 (ACU Address 13); 1.2.1-1.8.1 (ACU Address 14); 1.2.1-1.8.1 (ACU Address 15); 1.2.1-1.8.1 (ACU Address 16) | p. 87 |
