2006 Honda TRX350FA TRX350FEA ATV Service Manual (P/N C4085-91017)

• Covers Honda TRX680FA and TRX680FGA models with selectable 2WD/4WD, a three-speed Automatic Transmission, ESP manual-shift mode, and reverse
• Honda Motor Co., Ltd. Service Publication Office issue dated November 2005
• Contains 565 PDF pages organized into 26 sections covering engine, drivetrain, chassis, electrical systems, diagnostics, and troubleshooting
• Documents the 674.9cc longitudinal single-cylinder engine with OHV valve train, liquid cooling, dry-sump pressure lubrication, and PGM-FI
• Details the PCM-controlled powertrain, where engine control, transmission control, and selectable 4WD functions share sensors and diagnostic logic
• Includes model-specific wiring, cable and harness routing, connector locations, factory test values, and special-tool references

System and Component Specifications

This service manual is built around the measurements and limits needed for component-level repair work. Engine data includes a 102 x 82.6 mm bore and stroke, 9.2:1 compression ratio, 40 mm throttle bore, and valve clearances of 0.15 mm (0.006 in) intake and 0.33 mm (0.013 in) exhaust. PGM-FI specifications include 1,400 ± 50 rpm idle speed, 284–304 kPa (41–44 psi) fuel pressure, and a minimum fuel-pump flow of 71 cm³ in 10 seconds at 12 V.

The lubrication and transmission data is equally specific. Engine oil capacity is 2.7 L after draining, 2.9 L with filter change, and 4.1 L after disassembly. Honda specifies 785 kPa (114 psi) at 5,000 rpm and 80°C for the oil-pressure line; the 1st, 2nd, and 3rd shift-clutch circuits use the same pressure value. The Automatic Transmission uses a torque converter and three hydraulically operated wet multi-plate clutches, with engine oil serving as the transmission hydraulic fluid. The manual also gives clutch clearances and wear limits, a 108 N·m (80 lbf·ft) torque-converter lock-nut specification, front differential slip torque of 14–17 N·m with a 12 N·m service limit, and front/rear final-drive backlash limits.

Diagnostics, Electrical, and Special Tools

The PCM integrates the engine and transmission control functions with selectable 4WD control, so the diagnostic coverage goes well beyond basic fuel-injection fault codes. PGM-FI troubleshooting covers MAP, ECT, TP, IAT, injector, IACV, rear vehicle-speed sensor, and PCM/EEPROM faults. Drivetrain diagnostics cover the front final clutch, A/T clutch-pressure-control solenoid, shift solenoids, gear-position inputs, and shared sensor faults. The fail-safe strategy is documented as well: certain A/T faults disable automatic shifting and anti-creep operation and hold the transmission in 2nd gear, while selectable-4WD faults can default the machine to 2WD.

HDS coverage includes DTC, freeze-data and current-data readout plus PCM reset functions. The manual also provides MIL and drivetrain-indicator blink-code diagnosis when the HDS pocket tester is not used. Factory tool references include pressure gauge set 07406-0020005, fuel pressure gauge 07406-0040004, HDS pocket tester TDS 3557-0112-01, SCS connector 070PZ-ZY30100, test probe 07ZAJ-RDJA110, and differential inspection tool 07KMK-HCS0101.

Electrical and hydraulic diagnosis is supported by named illustrations rather than only component photos. Examples include the Lubrication System Diagram, PGM-FI System Diagram, Fuel Flow Chart, Shift Clutch Hydraulic Circuit and Operation, Automatic Transmission Performance Curve, and the TRX680FA/FGA Wiring Diagram. Separate connector-location and cable/harness-routing pages identify PCM connectors, shift-solenoid wiring, front and rear vehicle-speed sensors, front final-clutch wiring, IACV, injector, MAP/TP and ECT circuits. Variant-specific material also covers the GPS receiver on the GPS model and Australia-only horn circuitry.

Factory Repair Procedures and Service Limits

The repair scope reaches full mechanical teardown. Covered procedures include engine removal and installation; cylinder-head disassembly and inspection; valve-guide replacement and valve-seat refacing; camshaft, rocker-arm, cylinder and piston service; crankcase separation; crankshaft and balancer inspection; oil-pump overhaul and pressure testing; cooling-system testing and water-pump service; and sub-transmission and selector-cable work.

Transmission repair procedures include shift-valve-body service, torque-converter removal and inspection, shift-clutch/mainshaft disassembly and assembly, and electronic A/T/4WD diagnosis. The scope distinction matters: the torque converter and 1st shift clutch can be serviced with the engine installed, while the mainshaft and 2nd/3rd shift clutches require crankcase separation and engine removal. A faulty torque converter is treated as an assembly replacement rather than an internal rebuild.

Chassis sections cover front and rear suspension, steering shaft and tie rods, wheel hubs and knuckles, front differential/final-clutch work, rear final-drive gear contact and backlash inspection, drive shafts and universal joint service, plus DOT 4 brake-fluid replacement, bleeding, master-cylinder and caliper repair. Maintenance data ties these systems back to factory intervals, fluid capacities, tire pressures, toe settings, brake wear limits, and critical fastener torques.

Several manual-specific cautions are important during repair. The throttle body is factory preset; disturbing its white-painted fasteners can cause throttle-body malfunction. Coolant containing silicate inhibitors can prematurely wear the water-pump seals or block radiator passages, while tap water can contribute to engine damage. The PCM can be damaged by excessive voltage if its connectors are disconnected while current is flowing.

Always review the safety messages and handling procedures in the Honda publication before beginning repair work, especially around pressurized fuel, hot coolant, brake hydraulics, electrical circuits, and heavy engine removal.