Tennant T300/T300e: Decoding Tennant T300 Fault Codes & Control Board

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July 20, 2026 5 min read

SAFETY WARNING:Always set the key switch to OFF and unplug the main battery cable before disconnecting control module harness plugs or servicing electrical panels. Static discharge can destroy logic chips; wear a grounded ESD wrist strap attached to battery negative when handling bare circuit boards.

The Tennant T300 and T300e communicate electrical system status through two primary operator interface styles:

Standard Membrane / BDI Display (T300e & Standard T300): Uses a row of 5 Battery Discharge Indicator (BDI) LEDs. System faults appear as specific combinations of flashing and solid LEDs.
Pro-Panel LCD Display (Premium T300): Displays explicit 4-digit hexadecimal fault codes (e.g., 0x0106, 0x0704) directly on screen, providing granular detail on the precise sub-circuit causing the trip.

Membrane/BDI Interface: Pro-Panel LCD Touchscreen:

┌─────────────────────────┐ ┌─────────────────────────┐

│ [⚡] [●] [○] [●] [○] │ │ FAULT CODE: 0x0106 │

│ Flashing LED Pattern │ ────► │ Scrub Motor Short Fault │

└─────────────────────────┘ └─────────────────────────┘

When diagnosing a machine in the field, cross-reference BDI flash sequences or Pro-Panel hex codes against the fault matrix below before condemning expensive logic boards.

Use this factory reference table to quickly identify the root cause and immediate corrective actions for common T300/T300e fault codes:

LCD Fault Code	Condition	Primary Root Cause	Field Correction Step
0x0102	Scrub Board Power Loss	Blown in-line fuse; loose switched B+ power at Wire 6 (BLU) Pin J8-7.	Inspect 70A main line fuse FU1 and harness connector J8 Pin 7.
0x0106	Scrub Motor Short Fault	Shorted scrub motor winding or pinched Wire 24 (YEL) / Wire 12 (BRN).	Disconnect motor plug J10. Check winding resistance (< .2 Ohms) indicates internal motor short).
0x0107	Scrub Motor FET Fault	Damaged internal field-effect transistor (FET) on Machine Board or severe voltage drop during startup.	Check power and ground connections at J6/J7. If 24V supply is clean, replace Machine Control Module.
0x0501	Vac Motor Open Warning	Disconnected connector J10; worn vacuum motor carbon brushes; blown 20A breaker CB6.	Verify connector J10 is seated. Test 20A breaker CB6 and measure motor carbon brush length.
0x0507	Vacuum FET Fault	Failed vacuum output driver on main control board.	Replace Machine Control Module.
0x0704	ec-H2O CAN Comm Fault	ec-H2O module unpowered; 4A breaker CB2 tripped; failed M2 relay.	Check 4A CB2. Measure 24V DC at ec-H2O connector J12 Pins 11 & 12.
0x0910	Propel Breaker Tripped	30A CB4 tripped; i-Drive harness unplugged; transaxle motor bound or overloaded.	Reset CB4. Check i-Drive white 14-way connector and drive wheel rotation.
0xF103	Charger CAN Comm Fault	On-board charger lost power or CAN network line broken.	Power cycle machine. Perform CAN resistance check across YEL & GRN communication lines.

To avoid replacing a good control board when a peripheral sensor or motor is at fault, follow the SUN-I/O System Isolation Procedure. SUN-I/O checks four core board states: Switched power, Unswitched power, Negative ground, and I/O (Inputs/Outputs).

[Machine Function Fails to Actuate]

│

Step 1: Check SUN Board Power Supplies

(Unswitched B+, Switched KSI, B- Ground)

│

┌──────────────┴──────────────┐

Power Missing Power Present

│ │

Check Key Switch, CB1, Step 2: Check Component

& Main Power Cables [cite: 253, 285] Inputs to Board

│

┌─────────────┴─────────────┐

Inputs Missing Inputs Present

│ │

Check Microswitches Step 3: Measure

(SW4, SW8, Bail) [cite: 294, 309] Board Output

│

┌─────────────┴─────────────┐

Output Missing Output Present

│ │

Board FET Failed Harness, Relay,

(Replace Module) or Motor Issue

Step 1: Verify Board Supply Voltage (SUN)

Unswitched Positive (U): Probe Wire 1 (RED) at connector J6 on the Machine Control Module. Must read main battery voltage (24V DC nominal).
Switched Key Power (S): Probe Wire 6 (BLU) at connector J8 Pin 7 with key turned ON. Must read 24V DC. If missing, inspect key switch and 4A circuit breaker CB1.
Negative Ground (N): Probe Wire 13 (BLK) at connector J7. Measure voltage drop to main battery negative post (must be < .2 V DC).

Step 2: Verify System Logic Inputs (I)

If power supply is confirmed, test command inputs entering the module before blaming the board:

Scrub Head Down Signal: Lower deck pedal. Verify Wire 28 (GRY) at connector J4 Pin 5 drops from 5V DC to 0V DC.
Bail Switch Trigger: Squeeze motion bail. Verify Wire 30 (TAN) at Interface Module J4 Pin 2 grounds out (0V DC).

Step 3: Measure Component Board Output (O)

Command the function and measure output voltage directly at the board output terminals:

Scrub Motor Output: Measure across connector J10 Pins 1/2 (24/YEL) and J10 Pins 3/4 (12/BRN).

Result A (24V DC present, but motor doesn't run): Board output driver is working. The issue is downstream in the motor cable harness or worn motor carbon brushes.
Result B (Inputs valid, but 0V DC output): Internal board relay or driver FET has failed. Replace the Machine Control Module.

A frequent challenge in field repair is determining whether error code 0x0106 (Scrub Motor Short) or 0x0107 (Scrub Motor FET Fault) means the motor damaged the board, or if the board failed independently.

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Tech Tip to Prevent Secondary Board Failure: Never plug a newly installed Machine Control Module into an untested scrub or vacuum motor that previously caused a short circuit code. Always verify winding resistance to ground (> 1 M Ohms) before energizing a new board!

When replacing major electrical controls on the Tennant T300 series—such as the Interface Module, Machine Control Module, or i-Drive Propel Controller—the new hardware must be programmed to match the machine's specific physical options.

[PC / Service Laptop]

│

USB to Mini-USB Cable [cite: 369]

│

[Operator Console Programming Port] [cite: 369, 573]

│

┌──────────────────────┼──────────────────────┐

[Interface Module] [i-Drive Controller] [ec-H2O Module] [cite: 371, 372, 376]

Module Replacement Checklist:

i-Drive Propel Module: Replacement i-Drive controllers must have factory default parameters flashed using the Tennant Service Diagnostics Software via the USB port on the operator console.
Interface Module (LCD/Membrane): Stored machine configuration data (scrub deck type, battery profile, ec-H2O installation) must be uploaded to a new interface module upon replacement.
On-Board Battery Charger: Automatically receives battery profile configuration from the Interface Module upon initial power-up after replacement.

Technical Summary Checklist

Identify whether the machine uses BDI LED flash sequences or Pro-Panel 4-digit hex codes for diagnosis.
Apply the SUN-I/O method (Switched, Unswitched, Negative, Inputs/Outputs) to isolate board failures from peripheral faults.
Check motor winding resistance to ground before connecting replacement control boards to prevent repeat FET failures.
Remember that replacement Interface and i-Drive modules require firmware configuration using Tennant Service Diagnostics software.

Need OEM Tennant T300 Replacement Parts? Keep your equipment running at peak performance with factory-certified replacement components: Shop T300/T300e Parts

Tennant T300/T300e: Decoding Tennant T300 Fault Codes & Control Board Isolation- Part 3

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