Diode Circuit Inspection 
The resistance should be low in one direction and more than 10 times as much in the other direction. If any diode shows low or high in both directions, the diode is defective and the relay box must be replaced.
NOTE
The actual meter reading varies with the meter or tester used and the individual diodes, but generally speaking, the lower reading should be from zero to one half the scale.
Relay Box Internal Circuit

A: Headlight Circuit Relay
B: ECU Main Relay
C: Fuel Pump Relay
D: Starter Circuit Relay
E: Fan Relay
Relay Circuit Inspection
FuseExploded View
EO: Apply engine oil.
G: Apply grease.
L: Apply a non-permanent locking agent.
Lh: Left-hand Threads
MO: Apply molybdenum disulfide oil solution.
(mixture of the engine oil and molybdenum disulfide grease in a weight ratio
10:1)
R: Replacement Parts
S: Follow the specified t ...
Air Switching Valve
Air Switching Valve Operation Test
Refer to the Air Suction System Damage Inspection in the
Periodic Maintenance chapter.
Air Switching Valve Unit Test
Remove the air switching valve (see Air Switching Valve
Removal in the Engine Top End chapter).
Set the hand tester [A] to the × 1 ...
Fuel Pump Relay Inspection
Refer to the Relay Circuit Inspection in the Electrical System
chapter.
If the fuel pump relay is normal, check the wiring to the
fuel pump relay (see Fuel Pump Relay Circuit).
Special Tool - Hand Tester: 57001-1394
If the wiring is good, check the ECU for its ground and
power supply (se ...