EDI DIAGNOSIS SERVICE MANUAL NUMBER 22
Page 5E-48 90-860074--1 FEBRUARY 2002
Timing Actuator (Timing Solenoid Valve)
Scan Code: P1630
Blink Code: 1214
Malfunction Indicator Lamp: OFF
75409
12
ECM
68
51
BLU
RED
1
2
45
23
REDRED
RED
a
b
c
d
e
e
e
a-Fuel Injection Pump
b-Timing Solenoid Valve
c-Harness Connector
d-Sensor Ground (–)
e-Battery Supply Voltage (1 of 3)
CIRCUIT DESCRIPTION:
Determining the proper fuel injection point (timing) depends on the quantity of fuel, engine
rpm and coolant temperature. The ECM controls the timing using the signal from the number
one instrumented injector and corrects the timing to the nominal timing rate. Timing is
changed by modulating (adjusting) the pressure in the upper (high pressure) chamber to
injector opening pressure at the correct instant (timing). Adjustment of pressure is carried
out by an electric Timing Solenoid Valve which the ECM operates. The solenoid valve is
closed if power (12 volts) is removed. With the valve fully closed (no voltage - pressure
increases) start of injection is advanced. With the solenoid valve permanently opened
(voltage present - pressure reduction) start of injection is retarded. In the intermediate
range, the on/off ratio (the ratio of solenoid valve open to solenoid valve closed - sometimes
referred to as duty cycle) can be infinitely varied by the ECM. Excess pressure is discharged
into the lower chamber.
A failure in the Timing Fault circuit should set a Scan Code P1630.
CKT PIN
NAME
51 Solenoid
68 Battery Supply Voltage
45 Battery Supply Voltage
23 Battery Supply Voltage
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