Isuzu 4HK-1, Manual, Page: 6 / 50

6
Isuzu 4HK-1 and 6HK-1 Engine Overview (continued)
Inputs to 40 pin engine harness connector(continued):
•
The 2 wire crankshaft position sensor (CKP) is located on the flywheel housing at
the left rear corner of the engine. The CKP sensor detects 45 projections equally
spaced every 7.5° around the flywheel periphery. There is also a space (equal to 3
projections) to act as a top dead center (TDC) reference signal for the engine control
module (ECM). With these 45 pulses and the TDC reference signal, the ECM
calculates the engine speed and exact position of the crankshaft.
•
The 2 wire camshaft position sensor (CMP) is located on the cylinder head at the
rear of the camshaft gear. The camshaft position sensor detects a total of the
number of the cylinders in the engine plus an extra one. The extra hole indicates the
top dead center position of number 1 cylinder. Five through holes (four holes
arranged equally every 90° on the gear and one reference hole) on the camshaft
gear flange surface on the 4HK-1 Engine. Seven through holes (six holes arranged
equally every 60° on the gear and one reference hole) on the camshaft gear flange
surface on the 6HK-1 Engine. The camshaft position sensor indicates the rotational
position of the camshaft to the ECM. The CMP signal input, determines the crank
angle and the ECM can use it to control fuel injection and calculate the engine
speed. The crankshaft position sensor (CKP) typically controls these functions,
however it is done by CMP sensor if the CKP sensor is faulty.
Diagnostic aid
If there is relevant Error Code to the crankshaft (CKP) sensor and Camshaft (CMP)
sensor, the engine will not start until memory clear is performed.
If an intermittent trouble is suspected, the following may be the cause:
• Improper connection of harness connector
• Defective harness routing
• Worn harness cover
• Wire disconnection inside harness cover
•
The 3 wire boost pressure sensor is located in the piping to the intake manifold of
the engine. The sensor converts the boost pressure into the voltage signal and
sends it to engine control module (ECM). The ECM should detect a higher signal
voltage at a high boost pressure.
•
The 4 wire Exhaust Gas Recirculation (EGR) position sensor is installed in EGR
valve and detects the valve lift amount of EGR.
Note:
Do not disassemble the EGR position sensor. If it is faulty, replace it as EGR
valve assembly.