Isuzu 4HK-1 - Common Rail Pressure Sensor Circuit Description and Symptoms

Trouble Shooting 104
Description of circuit
The common rail pressure sensor detects the common
rail internal pressure. The common rail pressure sensor
is installed to the common rail. As the common rail
internal pressure changes depending on engine
condition, output voltage of the common rail pressure
sensor will change (if the common rail internal fuel
pressure is low, output voltage becomes low, if the
pressure is high, the output voltage becomes high as
well). The engine control module (ECM) reads this
output voltage change, converting it into common rail
internal pressure, to utilize for control. Dedicated
communication circuits are used for the sensor power
supply (5V), SIG, and ground in the common rail
pressure sensor, which are connected to the ECM.
Also, the sensor circuit is shielded to avoid electrical
noise etc.
Main trouble symptom
• Intense engine vibration
• Rough idling
• Output lowering
• Engine blow up fault
• Black smoke emitted
• Excessive output possible
Preconditions when Error Code is set
1st step
• Key switch input voltage is 18V or more.
• Error Code 0088, 0192, 0193, or 1635 is not
detected.
• Actual rail pressure is 2 MPa or more, and 70 rpm
or more.
2nd step
• Battery voltage is normal.
• Error Code 0088, 0192, 0193, or 1635 is not
detected.
• Actual rail pressure is 2 MPa or more, and 70 rpm
or more.
TSHK0028
5V
111 E-56
B+
0.75
W/R
8
5
E-80
0.75
B
5 E-80
94 E-56
0.75
G/B
4
1
E-80
103 E-56
B+
0.75
W/B
7
6
E-80
W
V
93 E-56
0.75
G/W
3
2
E-80
110 E-56
B+
0.75
W/L
6
7
E-80
92 E-56
0.75
G/Y
2
3
E-80
99 E-56
1
4
E-112
87 E-56
0.75
W
0.75
W
0.75
G
1
12
E-80
90 E-56
3
E-113
2
E-113
13
0.75
B
0.75
Br
0.75
W/R
98 E-56
2
5
E-112
3 E-112
0.75
B/W
1
E-113
6
82 E-56100 E-56
U
H-20 H-20 H-20
H-20
H-20
H-8
H-8
H-8 H-8 H-8 H-8
101 E-56
14
H-20
0.75
Br
Engine control
module (ECM)
EGR position sensor/EGR motor
EGR valve
Common rail pressure sensor
Common rail pressure
sensor signal
EGR position
sensor signal
EGR position
sensor signal
EGR position
sensor signal
CMP sensor
signal
CMP sensor