Dtc31 - Idle Up Volume System Fault - Isuzu 4HL1 Workshop Manual

DTC31 - Idle Up Volume System Fault

0.5
R/B
PTO Sensor
Circuit Description
The idle up volume switch controls the idle speed
during warm-up and is installed in the driver's side
instrument panel. This switch is active only when the
gear is in the neutral position (parking or neutral
position for automatic transmission vehicles). When the
shift lever is moved to another position, the switch is
canceled. The ECM receives the idle up signal from
this switch and controls the fuel injection quanti ty.
DTC31 will be set when the output signal is excessively
high or low.
Major Faulty Event
• Poor driveability
Conditions for Setting the DTC
The idle up volume output signal deviates from the
range between 0.2 V and 4.8 V for 1 second.
Action Taken When the DTC Sets
• Even after the DTC is set, the ECM will not
illuminate the CHECK ENGINE lamp (MIL).
• The idle up volume switch is disabled.
Conditions for Clearing MIL/DTC
When the system fails and the DTC is stored to the
ECM, even repairing the faulty portion will not clear the
34 31 71
0.5 0.5
Y Y/BR
30
0.5
Y/G
Idling
Control
DTC from the memory. To clear the DTC, conduct the
following steps.
1. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
2. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
3. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
4. Turn on the idle position switch for not less than 1
second but not more than 3 seconds. (Release the
accelerator pedal.)
5. Turn off the idle position switch for not less than 1
second but not more than 3 seconds. (Press the
accelerator pedal.)
6. After the above operations are properly completed,
the CHECK ENGINE lamp (MIL) illuminates for 3
seconds to report the memory is cleared.
7. Turn off the starter switch. Wait for 5 seconds and
turn on the starter switch again.
When Tech 2 has been connected to the vehicle, the
DTC can be cleared through the memory clear
operation with Tech 2.
Engine Control System 1A-123
VIM
(Vehicle
Interface
Module)
VS Sensor
LNW21AMF007801-X