Toyota Pallet Truck Service Manual Troubleshooting Electrical Troubleshooting Guidelines Electrical Troubleshooting Guidelines Whenever measuring resistance, turn the truck OFF and disconnect the battery connector. Battery current can damage an ohmmeter. For troubleshooting DC electric motors, see “DC Electric Motor Tests” on page 5-7. Many problems are caused by a faulty or dirty battery. Make sure the battery is clean. See “Battery” on page 6-8. For troubleshooting AC electric motors, see “AC Electric Motor Tests” on page 5-9. For information on fuses, see “Fuses” on page 6-14. Make sure you jack and block the pallet truck whenever a troubleshooting procedure requires turning the truck ON.
This will avoid accidents caused by unexpected truck travel. For information on pin, connector, and harness connections, see “List of Electrical Symbols” on page 5-15, “Wiring Harness” on page 6-12, and “AMP Harness/Traction Power Amplifier Connector” on page 6-27. For information on functions and normal voltages of terminals and harness connector pins refer to the pinout matrix chart on page 5-69. Unless otherwise directed, disconnect the battery connector when you examine electrical circuits or components with an ohmmeter. Electrical current can damage the ohmmeter. Troubleshooting the CAN Bus The CAN bus consists of two wires interconnecting the VM, TPA, and service port interface.
One wire is called CAN Hi and the other is called CAN Lo. All communications between the VM, TPA, and service port are performed over those two wires. Check these wires first if a communication problem arises or for any problem that could be related to the CAN Bus. Save time and trouble by looking for simple causes first. Visually inspect all wiring and electrical components for: Loose connections or connectors Loose or broken terminals Damaged terminals, blocks, or strips There is a 120 ohm terminating resistor in the VM and also one in the TPA. If the TPA has a jumper wire installed between JP1-21 and JP1-34, the resistor will terminate the bus wires at the TPA.
There is no jumper wire for the VM. Broken wiring and shorted conditions (especially those that are close to metal edges or surfaces) Use a digital multimeter such as a Fluke meter for all measurements. Analog meters can give inaccurate readings and load down sensitive electronic circuits enough to cause failure. Ensure meter cables are connected to the correct meter jacks and that the correct function and scale are selected. To check the CAN Bus wires between the VM and TPA and to test the terminating resistors, disconnect either the VM or TPA from the CAN bus.
If the resistor on the TPA and the wires from the VM to the TPA are checked, disconnect the wires going into the VM and measure the resistance from the CAN wires back to the VM. 120 ohm should be measured if the wires and resistor are good. If the resistor on the VM and 00700-CL398-07, Issued: 9 August 2007 5-3