Connect the indicator wire, and check whether the indicator is on or off in the working state, as shown in Figure 5-64 and Figure 5-65.
1. ST7126 is used to check the continuity of a single line. The indicator is on and the circuit is normal. .
2. S17123 is used to check the solenoid valve assembly circuit (for proportional solenoid valve and directional solenoid valve).
(1) Proportional solenoid valve and travel speed selector solenoid valve. When the corresponding joystick or switch works, the indicator light is on and the circuit is normal. :
(2) Rotary parking solenoid valve. When swinging and/or stick retracting, the indicator light is off and the circuit is normal. When the joystick is in neutral, the indicator light is on and the circuit is normal.
3. ST7130 is used to check the rotary buffer solenoid valve circuit. When the rotary joystick works, the indicator light is on and the circuit is normal.
4. ST7124 is used to check the pump displacement solenoid valve circuit (because the indicator light only lights up briefly, so be careful not to miss it). When the joystick is working, the indicator light is on and the circuit is normal (it is easier to check the operation of the boom).
5. ST7125 is used to check the EC motor circuit. When one of the power mode switches P, E, L or I is pressed, if the two indicator lights are on, the circuit is normal; if only one indicator light is on, the circuit where the indicator is off is faulty; if the two indicators If none of the lights are on, check the relay and wire.
6. ST7129 is used to check terminals 2 and 3 of EC sensor, A sensor and DP sensor.
7. ST7139
ST7139 lamp wire and ST7129 lamp wire are connected to the same connector (terminal 2) for adjusting the installation position of the A sensor. After connecting the S17139 lamp wire to the A sensor, the switch is turned off (OFF), the signal voltage becomes OV, and the pump displacement angle increases to the maximum value. Then, turn the switch ON, and adjust the installation position of the A sensor so that the signal voltage is equal to the specified signal voltage (4.4 +0.05) V.
8. ST7127
As shown in Figure 5-66, it is used to check the emergency relay circuit (only for Isuzu engine), when the engine is difficult to start or stop.
(1) T lamp: Check between terminals ACC and 4(T). The following states indicate that ACC (power supply) is supplying current to the engine oil pressure switch: (a) When the engine oil pressure switch is turned ON (the oil pressure is low), the T lamp is turned ON.
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(b) When the engine oil pressure switch is turned off (OFF), the T lamp is off (()FF) (dimmed).
(2) ACC lamp: Check between terminals ACC and 3(E). The following states indicate that ACC (power) is supplying current to the engine stop relay: (a) When the key switch is in the ON or START position, the ACC light is on. (b When the key switch is in the OFF position, the ACC lamp is off.
(3) PI lamp: Check between terminals 2 (P1) and 3 (E). The following states indicate that the engine stop motor is in the fuel supply position: (a) When the engine is running (the key switch is on (ON> position), the P1 light is on. (b) When the engine is started (the key switch is in the START position)) At the time, the P1 light is on. (e) When the engine is stopped (the key switch is in the OFF position), the P1 light is off.
(4) P2 lamp: Check between terminals 5 (P2) and 3 (E). The following states indicate that the engine stop motor is in the fuel cut-off (closed) position: (a) When the engine is stopped (the key switch is in the OFF position), the P2 light is on. (b) When the engine starts (the key switch is in the start position), the P2 light goes out. (c) When the engine is running (the key switch is in the on position), the P2 light is off.
(5) P2' lamp: check between terminals 6 (P2') and 3 (E). The following states indicate that the engine stop (fuel cutoff) signal is sent from the emergency relay to the engine stop motor: (a) When the engine is stopped (the key switch is in the ON or OFF position), the P2' light is on. (b) When the key switch is in the HEAT, ACC, or START position, the P2’ light turns off.
(6)c lamp: Check between terminals 1(c) and 3(E). The following states indicate that the engine start signal is sent from the key switch to the emergency relay: (a) When the key switch is in the START position, the C light is on. (b) When the key switch is in any position other than the start position, the C lamp is off.
9. ST7128
As shown in Figure 5-67, it is used to check the engine stop motor circuit (only applicable to Isuzu engines), when the engine is difficult to start or stop.
(1) A lamp: Check between terminals 1 (A) and 5 (E). The following states indicate that the engine stop motor drive signal is sent from the engine stop relay: (a) Start the engine, turn the key switch to the OFF position, and the A light is on.
(b) When the engine is stopped, move the key switch to the START position, and the A light is on. (c) When the engine is running or stopped, the A lamp is off.
(2) B lamp: Check between terminals 3 (B) and 5 (E). Whenever the B light is on, it means that the battery voltage is supplied to the engine stop motor.
(3) P1 lamp: Check between terminals 4 (P1) and 5 (E). The following states indicate that the engine stop motor is in the fuel supply position: (a) When the engine is running (the key switch is in the ON position), the PI light is on. (b) When the engine is started (the key switch is in the START position), the P1 light is on. (c) When the engine is stopped (the key switch is in the OFF position), the P1 light is off.
(4) P2 lamp: Check between terminals 2 (P2) and 5 (E). The following states indicate that the engine stop motor is in the fuel cut-off (closed) position: (a) When the engine is stopped (the key switch is in the OFF position), the P2 light is on. (b) When the engine starts (the key switch is in the START position), the P2 light goes out.
