Isuzu N-Series. Manual - part 433

6E-68 EMISSION AND ELECTRICAL DIAGNOSIS

DTC-P26 Quick Warm System (QWS) Relay Control Circuit High Voltage

N6A1183E

EMISSION AND ELECTRICAL DIAGNOSIS 6E-69

Location of Relay

Legend

1. Relay box (Installed on the left side rear of the 

cab)

N6A1184E

NO

RELAY NAME

X-20

Glow plug

X-21

Starter

X-22

Marker lamp

X-23

Rear fog

X-24

A/C COMP, 4WD ind. lamp

X-25

Exh, Brake control

X-26

CSD, A/C ON SIGNAL

X-27

Condenser fan

X-28

Exh. Brake cut

6E-70 EMISSION AND ELECTRICAL DIAGNOSIS

Inspection for Timing Advance Solenoid Switch cut
relay

Resistance value

Legend

A. Timing advance solenoid

N6A1175E

N6A1176E

N6A1177E

Inspection Point

Resistance

Reference

Inspection 
relay unit

2 

←→ 4

240 to 290 (

Ω) (for 12 volt)

256 to 276 (

Ω) (for 24 volt)

1 

←→ 5

∞

Not be supplied electricity

Below 0.5 (

Ω)

Be supplied electricity

3 

←→ 5

Below 0.5 (

Ω)

Be supplied electricity

∞

Not be supplied electricity

EMISSION AND ELECTRICAL DIAGNOSIS 6E-71

Step

Action

Value

YES

NO

1

Was the “on-board diagnostic (OBD) system
check” performed?

—

Go to Step 2

Go to self diag 

system check

2

1. Ignition “OFF”, with scan tool disconnect-

ed.

2. Disconnect the Relay solenoid switch

from the Relay box.

3. Apply a circuit tester with the voltage

range or a test light to the output circuit for
the Relay.

4. Ignition “ON”, Engine “OFF”.

Is voltage as prescribed, or is test Light lit until
18 seconds?

≥8 V or light 
“ON” (for 12 

Volt)

≥16 V or light 

“ON” (for 24 

Volt)

Go to Step 3

Go to Step 4

3

1. Ignition “OFF”
2. Disconnect the ECM connector from

ECM.

3. Check the short to voltage of Relay circuit

between the ECM and Relay connector.

4. Repair if necessary.

Has DTC 26 been corrected?

—

Go to Step 6

Go to Step 5

4

Replace the Relay.

Is the action complete?

—

Go to Step 6

—

5

Replace the ECM.

Is the action complete?

—

Go to Step 6

—

6

1. Reconnect all the connectors removed.
2. Ignition “ON”, Engine “OFF”

Is DTC 26 all right under Scan Tool Check?

—

Go to Step 7

Go to Step 2

7

Is any current trouble other than DTC 26 dis-
played by scan tool?

—

Go to trouble code 

section

Trouble code clear