If you’ve ever found yourself staring at a flashing number on your Hyster or Yale forklift’s screen and thinking, “Okay… what now?”, you’re not the only one. Yale and Hyster forklifts are known for their strength, durability, and reliability in high-demand environments. But like any smart machine, they come with onboard diagnostics, and when something’s off, they flash a code. And those codes? They’re not just random digits. They’re how your forklift communicates. They’re early warnings, subtle alerts, and sometimes, urgent red flags that shouldn’t be ignored.
Here at Forklift Toronto, we have Hyster forklifts for sale and Yale forklifts for sale in Toronto. We also supply forklift parts for these brands to keep your machines working great. We work hands-on with businesses throughout the GTA, teams running non-stop operations, juggling pressure, performance, and tight turnarounds.
We know how fast things can fall behind when a forklift goes down. That’s why we’ve created this clear, practical Yale and Hyster forklift fault codes list, so you can spend less time guessing and more time moving. Whether you’re looking to diagnose an issue quickly or stay one step ahead of costly downtime, this code list and fixing guide is built to help, simple, direct, and right when you need it.
This fault-code list and fix guide is your go-to reference for Yale and Hyster Forklift Errors—meanings, causes, and quick fixes, right when you need them.
| Fault code | Description | Possible causes | How to fix |
| AL01 | traction and hoist functions not working | There is an incomplete connection between the control card and the controller; the traction reversing switch is not connected; or the tiller card is faulty or damaged. | Inspect and secure the connections between the control card and the controller; use a diagnostic handset to verify the function of the traction reversing switch; replace the control card if the tiller card is found to be damaged. |
| AL02 | traction and hydraulic functions not working | The main contactor contacts might be stuck together (welded closed), or there could be a break in the motor field circuit. | Disconnect the power wires from the contactor and test to see if the circuit is open; also, check all the connections between the motor field and the controller to make sure everything’s properly connected. |
| AL4 | traction and hydraulic functions not working | There’s a damaged connection to the lowering valve, or the lowering coil or valve cartridge itself is faulty. | Inspect the electrical connection between the valve coil and the controller; test the lowering valve coil’s resistance and replace it if it’s not close to 17.7 ohms; replace the lowering valve cartridge if needed. |
| AL5 | traction and hydraulic functions not working | There’s a problem with the connection to the brake, or the brake coil is damaged. | Check the wiring between the electric brake and the controller; test the brake coil’s resistance in both directions and replace it if the resistance isn’t between 27.36 and 30.24 ohms. |
| AL6 | traction and hydraulic functions not working | There’s a damaged connection to the traction motor; the traction motor armature resistance is too low; the field wires are loose or damaged; or the motor field winding is shorted or has too low resistance. | Inspect the electrical connections between the traction motor, field wires, and controller; test the traction motor armature for shorts; check the motor field resistance and make sure it’s between 0.5 and 1.5 ohms; also, check the contactor coil resistance, which should be around 52 ohms. |
| AL7 | traction functions reduced below 14°F or above 167°F and not working above 194°F | The controller’s temperature is either too high or too low; the temperature sensor isn’t calibrated properly; or the sensor or controller is damaged. | Move the truck to a warmer or cooler spot as needed; use a diagnostic handset to compare the controller’s temperature reading with the actual room temperature; if they don’t match, the controller may need to be replaced. |
| AL8 | traction and hydraulic functions not working | There’s an overcurrent in one of the driven components. | Inspect the main harness for any damaged connections to the main contactor, brake, and electric valve coils; also, check the condition of the contactor and brake. |
| AL66 | hydraulic function not working | The battery voltage is low, or the controller’s voltage calibration is off. | Charge or replace the battery; if the problem persists, use a diagnostic handset to check the voltage the controller is reading and compare it to a real voltmeter; if there’s a difference of more than 1.5 volts, replace the controller. |
| AL99 | traction and hydraulic functions not working | The wrong battery is being used, the battery is damaged, or there’s a faulty connection to the battery. | Make sure you’re using the correct voltage battery for your truck, manually test the battery’s voltage, inspect the battery for any damage, and check the battery cables and connectors for any issues. |
| 524223-0 | XMSN Reverse Pressure Greater Than Commanded Pressure | Possible causes include an open or broken sensor power supply wire, a sensor that has malfunctioned due to age or damage, mechanical issues in the transmission causing abnormal pressure readings, or failure within the controller’s processing circuits. | Begin by inspecting the sensor power supply wiring harness for any breaks, corrosion, or loose connections. Test the sensor output with a multimeter or scan tool to verify it’s operating within specs. Inspect mechanical parts related to reverse pressure (valves, seals). If sensor and wiring are fine, test and possibly replace the controller module controlling transmission pressures. |
| 524225-0 | XMSN Forward Pressure Greater Than Commanded Pressure | Causes can include electrical issues such as power supply opens or shorts, a faulty sensor outputting incorrect pressure readings, mechanical blockage or wear causing excess pressure, or a failing controller unable to correctly interpret or command pressure levels. | Check wiring for sensor power and signal integrity; repair any damaged wires. Use diagnostic tools to monitor sensor output during operation. Inspect transmission components for wear or blockages that could increase pressure. Replace sensor if faulty. If problem persists, test and replace the controller. |
| 524223-1 | XMSN Reverse Pressure Less Than Commanded | Possible causes include low or insufficient transmission fluid levels, sensor power supply faults, sensor internal failure, mechanical problems reducing pressure, or issues with the controller misreading sensor data or commanding pressure incorrectly. | Check and top off transmission fluid levels to manufacturer specifications. Thoroughly inspect sensor wiring for opens or shorts. Test sensor function using diagnostics and replace if defective. Inspect transmission for mechanical faults (worn pumps, valves). If no mechanical or sensor issues, test controller output signals and replace controller if needed. |
| 524225-1 | XMSN Forward Pressure Less Than Commanded | Similar causes to reverse pressure low: low fluid, electrical faults in sensor power or signal lines, sensor malfunction, mechanical failure (worn parts, stuck valves), or controller malfunction. | Verify transmission fluid levels are adequate and at correct temperature. Inspect and test sensor wiring and sensor outputs. Examine transmission internals for issues reducing pressure generation. Use diagnostics to verify controller commands and sensor feedback. Repair or replace faulty components accordingly. |
| 105-3 | Intake Air Temperature (IAT) Sensor OORH | Causes include an open circuit in the wiring harness, sensor signal wire shorted to 5V reference voltage or battery voltage, sensor internal failure due to exposure or contamination, or controller input circuitry malfunction. | Visually inspect wiring harness and connectors for damage, corrosion, or loose connections. Use a multimeter to check for shorts between sensor signal and 5V or battery voltage. Replace the IAT sensor if faulty. Reset error codes and monitor sensor data live to verify fix. If issue remains, test controller inputs and replace controller if defective. |
| 110-3 | Coolant Temperature Sensor OORH | Wiring may have an open circuit or short to battery voltage, sensor itself could be damaged or failing, or the engine controller’s coolant temp sensor input may be malfunctioning. | Perform continuity and resistance tests on coolant sensor wiring. Inspect connectors for corrosion or damage. Replace coolant temp sensor with OEM part if testing indicates failure. Clear codes and monitor sensor readings. If problem persists, consider controller repair or replacement. |
| 177-3 | Transmission Oil Temperature Sensor OORL | Possible wiring harness open circuit or short to 5V or battery voltage, sensor internal failure due to heat or wear, or controller input circuit failure. | Inspect sensor wiring harness and connectors for damage or corrosion. Use diagnostic tools to check sensor resistance and signal voltages at operating temperatures. Replace sensor if readings are abnormal. If wiring and sensor are good, test controller sensor inputs and repair/replace as needed. |
| 522603-3 | Fuel Temp (LPG) Sensor OORH | Wiring open, shorted to 5V or battery voltage, sensor internal failure due to contamination or wear, or engine control module malfunction. | Inspect wiring harness thoroughly for breaks or shorts. Replace the fuel temperature sensor with a known good unit. Clear fault codes and verify sensor readings during operation. Test ECM inputs for proper operation; replace if necessary. |
| 105-4 | Intake Air Temperature (IAT) Sensor OORL | Sensor signal shorted to ground or open circuit wiring, sensor internal failure, or controller malfunction causing low or no sensor voltage signal. | Check wiring harness for shorts to ground or open circuits. Replace sensor if resistance readings are out of spec. Inspect connector terminals for corrosion. Verify controller sensor input voltages and replace controller if proven faulty. |
| 110-4 | Coolant Temperature Sensor OORL | Wiring open or shorted to ground, sensor internal failure, connector issues, or controller sensor input failure causing low sensor signal voltage. | Test wiring harness for continuity and shorts to ground. Replace coolant temperature sensor if necessary. Clean or replace corroded connectors. Use diagnostic tools to check sensor voltages and replace controller if input circuitry is malfunctioning. |
| 177-4 | Transmission Oil Temperature Sensor OORL | Wiring open circuit, short to ground, sensor internal fault, connector issues, or controller input failure. | Inspect wiring and connectors for damage or corrosion. Replace sensor after verifying fault. Use diagnostic equipment to test sensor signal voltage under operating conditions. Replace controller sensor input circuitry if wiring and sensor are confirmed good. |
| 522603-4 | Fuel Temp (LPG) Sensor OORL | Wiring open or shorted to ground, sensor failure, connector damage, or controller input malfunction resulting in low or no sensor signal. | Inspect and repair wiring harness, focusing on shorts to ground. Replace the fuel temperature sensor if out of spec. Check connector terminals for corrosion or poor contact. Test controller inputs and replace controller module if needed. |
| 522712-3 | Accelerator A Position Sensor OORH | Sensor power supply wiring open or shorted to battery or 5V reference, sensor signal open or shorted to battery, sensor internal failure, or controller failure in interpreting sensor signals. | Inspect sensor power supply wiring for breaks or shorts. Use multimeter to check sensor signal wiring integrity. Replace accelerator position sensor A if faulty. Verify controller sensor input voltages; replace controller if sensor wiring and sensor are good but fault persists. |
| 522713-3 | Accelerator B Position Sensor OORH | Same causes as Accelerator A: sensor power supply or signal wiring open or shorted, sensor failure, or controller input malfunction. | Inspect wiring harness and connectors, test sensor output signals with diagnostic tools, replace sensor B if needed. Check controller sensor input; replace controller if no wiring or sensor faults found. |
| 522712-4 | Accelerator A Position Sensor OORL | Sensor signal open or short to ground, sensor power supply wiring open, sensor failure, or controller malfunction leading to loss or insufficient sensor signal. | Repair wiring harness open circuits or shorts to ground. Replace accelerator position sensor A if sensor is defective. Test controller inputs and replace if sensor and wiring are verified to be good. |
| 522713-4 | Accelerator B Position Sensor OORL | Similar to sensor A: wiring open or shorted to ground, sensor internal failure, or controller malfunction causing low or no sensor signal. | Inspect wiring for open or short circuits, replace sensor B as needed. Check controller sensor inputs and replace controller if wiring and sensor test normal. |
| 1079-31 | 5VE1 & 5VE2 Simultaneously OORH | The throttle assembly may be physically stuck or binding, sensors 5VE1 and 5VE2 could be faulty or misaligned, wiring harness problems, or controller failing to correctly process signals. | Inspect throttle body and linkage for dirt, corrosion, or mechanical binding; clean or lubricate as needed. Check sensor alignment and operation; replace if faulty. Verify wiring harness integrity. If hardware is fine, test and replace controller module. |
| 51-2 | Throttle Position Sensor Signals A and B Not Tracking Correctly | Sensor signals A and B not correlating due to misalignment, sensor wear, wiring damage, or calibration errors in the controller. | Perform sensor calibration procedures per manufacturer instructions. Inspect wiring harness for damage. Replace throttle position sensors if misalignment or sensor wear is confirmed. Use diagnostic tools to verify correct sensor tracking. |
| 51-7 | Throttle Position Sensor Signals A and B Not At Commanded Value | Sensors may be outputting incorrect voltage levels due to internal faults, wiring issues, or controller calibration problems causing mismatch with expected values. | Test sensor output voltages against specifications. Repair or replace wiring if damaged or corroded. Calibrate or replace sensors as needed. Update or replace controller firmware if calibration problems persist. |
| 51-31 | Throttle Position Sensor 1 & 2 Out of Range | Sensor readings outside expected operating ranges possibly due to sensor failure, wiring issues, or physical damage to throttle body. | Inspect and test sensor outputs for correct voltage ranges. Repair wiring or replace sensors. Check throttle body for mechanical damage or binding. Replace controller if necessary. |
| 2350-3 | Front Work Lights Relay (RL4) Driver Output OORH | Safety switch disconnected or faulty, relay coil wiring shorted to battery voltage, open or broken relay coil or ground wiring, or controller driver output failure. | Check safety switch wiring and operation. Repair wiring shorts to battery or broken connections. Test relay coil resistance and replace relay if defective. Test controller output pins and replace controller module if faulty. |
| 522710-3 | Throttle A Position Sensor OORH | Sensor ground wire open, sensor signal shorted to supply voltage or battery, sensor internal failure, or controller input malfunction. | Inspect wiring harness for open ground wires or shorts to supply. Replace throttle A sensor if testing shows fault. Verify controller sensor input voltages and replace controller if needed. |
| 522711-3 | Throttle B Position Sensor OORH | Similar issues as throttle A sensor: wiring open or shorted, sensor internal failure, or controller malfunction | Check wiring harness and connectors. Test sensor B output signals and replace sensor if faulty. Verify controller inputs. |
| 522710-4 | Throttle A Position Sensor OORL | Sensor signal open circuit, supply open circuit, short to ground, sensor internal fault, or controller sensor input failure causing low or no sensor voltage. | Repair wiring open circuits or shorts to ground. Replace sensor if defective. Test controller inputs and replace if necessary. |
| 522711-4 | Throttle B Position Sensor OORL | Sensor signal open circuit, supply open circuit, short to ground, sensor internal fault, or controller sensor input failure causing low or no sensor voltage, for throttle B. | Inspect and repair wiring harness, replace sensor B if faulty. Test controller sensor input circuits and replace controller if needed. |
| 521-3 | Brake Pedal Position Sensor OORH | Sensor ground open, signal shorted to supply or battery voltage, sensor failure, wiring damage, or controller input fault causing high sensor voltage. | Check wiring harness for open ground or shorts to supply voltage. Replace brake pedal sensor if testing shows faults. Test controller inputs and replace if faulty. |
| 523780-3 | Park Brake Position Sensor OORH | Same causes as brake pedal sensor: wiring open or shorted to supply, sensor malfunction, controller input issues. | Inspect and repair wiring harness. Replace park brake sensor if defective. Verify controller sensor input voltages and replace controller if necessary. |
| 524245-3 | Seat Occupancy Position Sensor OORH | Wiring harness open, shorted, sensor failure due to mechanical damage or contamination, controller input circuit failure. | Inspect wiring and connectors for damage or corrosion. Replace seat occupancy sensor if faulty. Test controller input and replace if sensor and wiring are good. |
| 521-4 | Brake Pedal Position Sensor OORL | Sensor supply open, signal open, short to ground, sensor internal failure, wiring harness issues, or controller sensor input fault causing low sensor voltage. | Repair wiring harness for opens or shorts to ground. Replace sensor if faulty. Test controller sensor input and replace controller if necessary. |
| 523780-4 | Park Brake Position Sensor OORL | Same causes as brake pedal sensor OORL: wiring open or short to ground, sensor failure, controller malfunction. | Inspect wiring, replace sensor as needed, test and replace controller module if required. |
| 524245-4 | Operator Presence System Sensor OORL | Wiring harness open or shorted, sensor failure, contamination or mechanical damage, controller sensor input malfunction. | Repair wiring harness, replace sensor. Test controller input voltages and replace controller if sensor and wiring are confirmed good. |
| 523833-3 | Glow Plug Relay Driver Output OORH | Relay coil shorted to battery voltage due to wiring shorts or internal relay coil failure, or controller output driver malfunction. | Inspect relay wiring for shorts to battery voltage. Replace glow plug relay if coil is shorted. Test controller driver output pins and replace controller if faulty. |
| 524195-3 | Cold Start Relay Driver Output OORH | Wiring short to battery voltage, relay coil failure, or controller output driver fault causing high voltage output. | Repair wiring shorts to battery. Replace cold start relay if defective. Test and replace controller output drivers if problem persists. |
| 523833-4 | Glow Plug Relay Driver Output OORL | Relay coil shorted to ground or controller output driver fault causing low voltage output. | Inspect wiring for shorts to ground. Replace relay if coil is shorted. Test and replace controller driver output circuitry as needed. |
| 524195-4 | Cold Start Relay Driver Output OORL | Relay coil shorted to ground or controller output driver fault causing low voltage output for cold start relay: wiring short to ground, relay coil failure, or controller output fault causing low voltage output. | Repair wiring shorts to ground. Replace relay if coil is defective. Test and replace controller if output driver circuit is faulty. |
| 1079-31 | 5VE1 & 5VE2 Simultaneously OORH (duplicate) | 5V supply shorted to system power, wiring harness faults causing cross voltage, or controller sensor input failure. | Inspect wiring harness for shorts between 5V sensor supplies and system power. Repair wiring faults. Replace controller if input circuit damaged. |
| 524260-3 | 5VE2 Sensor Supply Circuit Voltage OORH | Sensor supply voltage high due to wiring short to higher voltage, damaged sensor regulator, or controller input failure. | Check wiring harness for shorts to battery or higher voltage. Replace sensor if internal regulator faulty. Test and replace controller if necessary. |
| 524261-3 | 5VE1 Sensor Supply Circuit Voltage OORH | a. the 5-volt “e1” supply is accidentally connected to the main system power, causing a short.b. the 5-volt “e2” supply is also shorted to the system’s main power source.c. both 5-volt “e1” and “e2” supplies are shorted to the system power at the same time.d. there is a malfunction or failure inside the controller itself. | Inspect wiring harness and sensor. Repair wiring shorts. Replace sensor or controller if faulty. |
| 96-3 | Fuel Level Sensor OORH | Sensor signal wire shorted to battery voltage, open circuit wiring, sensor internal failure, or connector corrosion causing high sensor voltage reading. | Inspect and repair wiring harness for shorts or open circuits. Replace fuel level sensor if defective. Clean or replace corroded connectors. Verify sensor signals after repair. |
| 96-4 | Fuel Level Sensor OORL | Sensor signal low due to open circuit, short to ground, wiring damage, sensor failure, or poor connector contact. | Check wiring harness for opens or shorts to ground. Replace sensor if faulty. Clean connectors. Verify sensor outputs after repair. |
| 523833-3 | Glow Plug Relay Driver Output OORH (duplicate) | Relay coil shorted to voltage, wiring fault causing relay coil overload, controller driver output malfunction. | Repair wiring harness shorts. Replace relay coil. Test and replace controller output drivers if necessary. |
| 523920-3 | REV Circuit Shorted High | Wiring harness shorted to battery voltage, relay coil internal short, or controller output fault causing high voltage. | Inspect and repair wiring shorts. Replace relay coil if defective. Test controller output circuits and replace controller if needed. |
| 523930-3 | FWD Circuit Shorted High | Same as above for forward circuit relay coil short or wiring harness short to voltage. | Repair wiring, replace relay coil, test controller driver output pins. |
| 552752‑4 | Transmission Internal Noise | A. Internal transmission component wear or damageB. Faulty transmission sensorC. Transmission fluid contaminationD. Sensor signal degradation | Inspect transmission for mechanical issues; check sensor wiring; flush and replace transmission fluid if needed; test and replace faulty sensors. |
| 100‑3 | Engine Oil Pressure OORH (Over-Range High) | A. Short to battery or 5V on oil pressure sensor circuitB. Faulty engine oil pressure sensorC. Controller malfunction | Check for wiring shorts; inspect and test the oil pressure sensor; replace sensor or controller if necessary. |
Let’s be honest, if you’ve ever had a forklift go down right in the middle of a busy shift, you know it’s not just a minor inconvenience. It’s a full-on halt. Things stop moving, everyone’s waiting, and the clock doesn’t stop ticking. That’s why, here at Forklift Toronto, we take our role seriously. We’re not just in the business of selling equipment, we’re in the business of keeping businesses running.
Whether you’re managing a warehouse, a distribution center, or a small local operation, your equipment matters. That’s why we offer a solid range of both Yale and Hyster forklifts for rent and sale in Toronto, two of the most trusted names in the industry. These machines are built for performance and longevity, and we stand behind every single one we deliver. We also stock a wide selection of OEM and aftermarket parts, so when something breaks, you’re not left scrambling.
But more than that, we’re also your go-to team for forklift repair services in Toronto. Our techs know these machines inside and out. We’ve seen what happens when sensors glitch, when a controller misfires, when one tiny issue snowballs into hours of downtime. And we know how to fix it fast. Because we’ve been there too. We get how stressful and costly unexpected breakdowns can be. And it’s why we’re so big on forklift service maintenance.
Regular service isn’t just about oil changes or battery checks. It’s about peace of mind. It’s about knowing your machines are safe, reliable, and ready to go every time you turn the key. Our maintenance plans are flexible, personalized, and built around your schedule, not ours.
In the end, we’re more than just another equipment supplier. We’re a team of real people who care about your uptime and your bottom line. So whether you’re exploring your options, looking for reliable repairs, or just curious about the top 10 forklift brands out there, give us a call, send us an email, or stop by. We’re always here to help you with your material handling needs.