Isuzu N-Series. Service manual - part 900

Transmission Control System (Smoother) 7A-55

1. Turn OFF the ignition for 30 seconds.
2. Keep the test lamp with connected.
3. Disconnect the ECM harness connector (J-

191 connector).

4. Turn ON the ignition, with the engine OFF.

Does the test lamp illuminate?

—

Go to Step 11

Go to Step 31

Repair the open circuit or high resistance on the
ground circuit of the starter cut relay switch side
between the starter cut relay (pin 1 of X-26
connector) and the chassis ground (J-9).

Did you complete the repair?

—

Go to Step 33

—

Repair the open circuit or high resistance on the
starter relay control circuit to the starter cut relay
switch side between the starter relay (pin 5 of X-21
connector) and the starter cut relay (pin 4 of X-26
connector).

Did you complete the repair?

—

Go to Step 33

—

Repair the short to ground on the starter cut relay
control circuit between the TCM (pin 16 of B-425
connector) or ECM (pin 14 of J-191 connector) and
the starter cut relay (pin 5 of X-26 connector).

Did you complete the repair?

—

Go to Step 33

—

Replace the starter cut relay.

Did you compete the replacement?

—

Go to Step 33

—

1. Turn OFF the ignition.
2. Replace the starter relay with the glow relay or

replace with a known good relay.

3. Put the vehicle with the following conditions:

• Selector lever N position
• Release the brake pedal
• Release the parking brake
• Emergency switch OFF

4. Attempt to start the engine.

Does the engine crank?

—

Go to Step 29

Go to Step 14

1. Turn OFF the ignition.
2. Remove the starter relay.
3. Inspect for an intermittent, for poor

connections and corrosion at the harness
connector of the starter relay (pins 1, 2, 4 and
5 of X-21 connector).

Did you find and correct the condition?

—

Go to Step 33

Go to Step 15

Probe the starter relay battery voltage feed circuit
(pin 2 of X-21 connector) with a test lamp that is
connected to a known good ground.

Does the test lamp illuminate?

—

Go to Step 16

Go to Step 23

1. Probe the starter relay ignition voltage feed

circuit (pin 4 of X-21 connector) with a test
lamp that is connected to a known ground.

2. Turn Start the ignition while observing the test

lamp.

Does the test lamp illuminate?

—

Go to Step 17

Go to Step 24

Step

Action

Value(s)

Yes

7A-56 Transmission Control System (Smoother)

1. Test the starter C terminal circuit between the

starter relay (pin 1 of X-21 connector) and the
starter C terminal for an open circuit or high
resistance.

2. Repair the circuit(s) as necessary.

Did you find and correct the condition?

—

Go to Step 33

Go to Step 18

1. Turn OFF the ignition.
2. Reinstall the starter relay.
3. Replace the emergency relay with the dimmer

relay or replace with a known good relay.

4. Put the vehicle with the following conditions:

• Selector lever N position
• Release the brake pedal
• Release the parking brake
• Emergency switch OFF

5. Attempt to start the engine.

Does the engine crank?

Go to Step 30

Go to Step 19

1. Turn OFF the ignition.
2. Remove the emergency relay.
3. Inspect for an intermittent, for poor

connections and corrosion at the harness
connector of the emergency relay (pins 1, 2, 3
and 5 of X-14 connector).

Did you find and correct the condition?

—

Go to Step 33

Go to Step 20

Probe the emergency relay ground circuits (pins 2
and 5 of X-14 connector) with a test lamp that is
connected to battery voltage.

Does the test lamp illuminate?

—

Go to Step 21

Go to Step 25

1. Probe the emergency relay voltage feed circuit

(pin 3 of X-21 connector) with a test lamp that
is connected to a known ground.

2. Turn ON the ignition, with the engine OFF.
3. Turn ON the emergency switch.

Does the test lamp illuminate?

—

Go to Step 22

Go to Step 26

1. Probe the starter relay control circuit to the

emergency relay switch side (pin 1 of X-14
connector) with a DMM that is connected to a
known good ground.

2. Turn OFF the emergency switch.
3. Turn Start the ignition while observing the

DMM.

Does the DMM voltage more than the specified
value?

18.0 volts

Go to Step 28

Go to Step 27

Repair the open circuit or high resistance on the
battery voltage feed circuit between the starter relay
(pin 2 of X-21 connector) and the battery terminal.
Check the Starter (60A) slow blow fuse (SBF-8) is
first.

Did you complete the repair?

—

Go to Step 33

—

Step

Action

Value(s)

Yes

Transmission Control System (Smoother) 7A-57

Repair the open circuit or high resistance on the
ignition voltage feed circuit between the starter relay
(pin 4 of X-21 connector) and the starter switch (pin
4 of B-67 connector). Check the Starter (10A) fuse
(F-22) is first.

Did you complete the repair?

—

Go to Step 33

—

Repair the open circuit or high resistance on the
ground circuits of the emergency relay between the
emergency relay (pins 2 and 5 of X-14 connector)
and the ground (B-7).

Did you complete the repair?

—

Go to Step 33

—

Repair the open circuit or high resistance on the
emergency switch voltage feed circuit between the
emergency relay (pin 3 of X-14 connector) and the
emergency switch (pin 5 of N-17 connector).

Did you complete the repair?

—

Go to Step 33

—

Repair the open circuit or high resistance on the
starter relay control circuit to the emergency relay
switch side between the starter relay (pin 5 of X-21
connector) and the emergency relay (pin 1 of X-14
connector).

Did you complete the repair?

—

Go to Step 33

—

Repair or replace the starter motor. Refer to starting
and charging system in the engine section.

Did you complete the repair?

—

Go to Step 33

—

Replace the starter relay.

Did you complete the replacement?

—

Go to Step 33

—

Replace the emergency relay.

Did you compete the replacement?

—

Go to Step 33

—

Important:
Replacement ECM must be programmed.
Replace the ECM. Refer to Engine Control Module
(ECM) Replacement /Restore Fuel Injector ID Code
Data in engine control section.

Did you complete the replacement?

—

Go to Step 33

—

Important:
Replacement TCM must be programmed and
learned.
Replace the TCM. Refer to Transmission Control
Module (TCM) Replacement in this section.

Did you complete the replacement?

—

Go to Step 33

—

Step

Action

Value(s)

Yes

7A-58 Transmission Control System (Smoother)

1. Reconnect all previously disconnected fuse,

relay or harness connector(s).

2. Clear the DTCs with the Tech 2 if stored.
3. Turn OFF the ignition for 30 seconds.
4. Put the vehicle with the following conditions:

• Selector lever N position
• Release the brake pedal
• Release the parking brake
• Emergency switch OFF

5. Attempt to start the engine.

Does the engine crank?

—

Go to Chart 1 of 3

Step 5

Go to Chart 1 of 3

Step 6

Step

Action

Value(s)

Yes

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