Isuzu D-Max / Isuzu Rodeo (TFR/TFS). Manual — part 611

ENGINE ELECTRICAL 6D – 51

QOS II PREHEATING SYSTEM

GENERAL DESCRIPTION

QOS II preheating system features a quick-on glow
plug with thermometer control of the glowing time and
the afterglow time function.

The system consists of a controller, indicator lamp,
thermoswitch, relay, and glow plug (4pcs).

With the employment of the thermoswitch, the glow
time changes according to the engine coolant
temperature, thus allowing optimum starting conditions
to be obtained.

6D – 52 ENGINE ELECTRICAL

SYSTEM DIAGRAM

QOS II Timing Chart

ENGINE ELECTRICAL 6D – 53

Inspection on QOS II System Operation

THERMO SWITCH

The thermo switch is located on the water outlet pipe.

Use a circuit tester to check the thermo switch for
continuity.
Thermo sensor (4JA1, 4JA1T, 4JG2T engine)

OFF

→ ON : 7 - 13°C (44.6 – 55.4°F)

ON

→ OFF : Below 3°C (37.4°F)

10

°C ON

OFF

3

°C

Thermo sensor (4JG2T engine)
Thermo Sensor Resistance

K-Ohm

Temperature

°C (°F)

Resistance

Temperature

°C (°F)

Resistance

-15

(5)

0

(32)

10

(50)

20

(68)

12.00

6.00
3.60
2.45

40 (104)
60 (140)
80 (176)

1.10
0.60
0.30

GLOW PLUG

Use a circuit tester to test the glow glugs for continuity.
Glow plug Resistance (Reference)

Ohms

Quick on start model

Approximately 0.9

6D – 54 ENGINE ELECTRICAL

QOS II SYSTEM TROUBLESHOOTING

1) Problems when the water temperature of the engine is 0°C or below.

Condition Cause

Circuit

Glow plug relay will
not be lit.

Bad connection of FLW between battery and starter.

Bad connection or disconnection of starter SW circuit

Bad connection or disconnection

Malfunction of other

of Fuse No . 8

circuits occurred

simultaneously.

Bad starter switch.

Bad connection of glow plug relay terminal.

Disconnection of glow plug relay excitation coil.

Disconnection of circuit between glow plug relay and timer.

Bad glow relay. (The main contact does not pass electricity.)

Bad connection of timer.

Bad timer.

Bad earth circuit of timer.

Bad thermoswitch. (It remains ON even in water temperature below 0°C.)

Earth short-circuiting of thermo SW.

3

2

1

6

7

7