Two Speed Rear Axle Shift Motor Diagnosis. Isuzu Isuzu MD Steel Tilt (F Model) 1999

For 1990-2009 cars only

Makes 🢒 Isuzu 🢒 1999 🢒 Isuzu MD Steel Tilt (F Model) 🢒 Driveline/Axle 🢒 Rear Axle Controls 🢒 Two Speed Rear Axle Shift Motor Diagnosis

Two Speed Rear Axle Shift Motor Diagnosis High Speed Inoperative

Step

Action

Value(s)

Yes

Did you complete the two-speed rear axle system check?

Go to Step 2

Refer to Two Speed Rear Axle System Check

Move the two-speed rear axle switch to HIGH.
Connect a J 39200 from CKT 241 (BRN) at the two-speed rear axle motor shift relay to the chassis ground.

Did the DMM read a battery voltage?

Go to Step 4

Go to Step 3

Locate and repair the open in CKT 241 (BRN).

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 4

System OK

Connect a J 39200 between the two-speed rear axle motor shift relay CKT 1469 (LT BLU) PIN 87 and the chassis ground.

Did the DMM read a battery voltage?

Go to Step 14

Go to Step 5

Connect a J 39200 between the two-speed rear axle motor shift relay CKT 1468 (LT BLU) PIN 87 and the chassis ground.

Did the DMM read a battery voltage?

Go to Step 7

Go to Step 6

Replace the two-speed rear axle motor shift relay.

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 7

System OK

Disconnect the two-speed rear axle motor shift relay.
Connect an J 39200 across the two-speed rear axle motor shift relay socket terminal 86 and the chassis ground.

Did the DMM detect continuity?

Go to Step 8

Go to Step 9

Replace the two-speed rear axle motor shift relay.

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 9

System OK

Disconnect the two-speed axle switch.
Connect an J 39200 across the two-speed axle switch terminal A and the chassis ground.

Did the DMM detect continuity?

Go to Step 11

Go to Step 10

Locate and repair the open in one or more of the following circuits:

•	CKT 21 (GRN/BLK or GRY/BLK)

•	CKT 416 (GRN/BLK or GRY/BLK)

•	CKT 1467 (GRN/BLK or GRY/BLK)

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 11

System OK

Connect an J 39200 across the two-speed axle switch terminal B and the chassis ground.

Did the DMM detect continuity?

Go to Step 12

Go to Step 13

Replace the two-speed axle switch.

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 14

System OK

Locate and repair the open in one or more of the following circuits:

•	CKT 22 (BLK)

•	CKT 16 (BLK)

•	CKT 27 (BLK)

•	CKT 26 (BLK)

•	CKT 160 (BLK)

•	CKT 152 (BLK)

•	CKT 21 (BLK)

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 14

System OK

Connect a J 39200 from CKT 1469 (LT BLU) at the two-speed rear axle shift motor PIN A to the chassis ground.

Did the DMM read a battery voltage?

Go to Step 16

Go to Step 15

Locate and repair the open in CKT 1469 (LT BLU).

Is the two-speed rear axle HIGH speed still inoperative?

Go to Step 16

System OK

Disconnect the two-speed rear axle shift motor.
Connect a J 39200 from CKT 450 (BLK) at the connector PIN B and the chassis ground.

Does the DMM indicate continuity?

Go to Step 17

Go to Step 18

Replace the two-speed rear axle shift motor.

Is the replacement procedure complete?

System OK

Locate and repair the open in CKT 450 (BLK).

Is the repair complete?

System OK

Two Speed Rear Axle Shift Motor Diagnosis Low Speed Inoperative

Step

Action

Value(s)

Yes

Did you complete the two-speed rear axle system check?

Go to Step 2

Refer to Two Speed Rear Axle System Check

Move the two-speed rear axle switch to LOW.
Connect a J 39200 from CKT 241 (BRN) at the two-speed rear axle motor shift relay to the chassis ground.

Did the DMM read a battery voltage?

Go to Step 4

Go to Step 3

Locate and repair the open in the CKT 241 (BRN).

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 4

System OK

Connect a J 39200 between the two-speed rear axle motor shift relay CKT 1468 (LT BLU) PIN 87A and the chassis ground.

Did the DMM read a battery voltage?

Go to Step 12

Go to Step 5

Connect a J 39200 between the two-speed rear axle motor shift relay CKT 1469 (LT BLU) PIN 87 and the chassis ground.

Did the DMM read a battery voltage?

Go to Step 7

Go to Step 6

Replace the two-speed rear axle motor shift relay.

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 7

System OK

Disconnect the two-speed rear axle motor shift relay.
Connect an J 39200 across the two-speed rear axle motor shift relay socket terminal 86 and the chassis ground.

Did the DMM detect continuity?

Go to Step 9

Go to Step 8

Replace the two-speed rear axle motor shift relay.

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 9

System OK

Disconnect the two-speed axle switch.
Connect the J 39200 across the two-speed axle switch terminal A and the chassis ground.

Did the DMM detect continuity?

Go to Step 10

Go to Step 11

Locate and repair the short to the ground in one or more of the following circuits:

•	CKT 21 (GRN/BLK or GRY/BLK)

•	CKT 416 (GRN/BLK or GRY/BLK)

•	CKT 1467 (GRN/BLK or GRY/BLK)

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 12

System OK

Replace the two-speed axle switch.

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 12

System OK

Connect a J 39200 from CKT 1468 (LT BLU) at the two-speed rear axle shift motor PIN C to the chassis ground.

Did the DMM read a battery voltage?

Go to Step 14

Go to Step 13

Locate and repair the open in CKT 1468 (LT BLU).

Is the two-speed rear axle LOW speed still inoperative?

Go to Step 14

System OK

Disconnect the two-speed rear axle shift
Connect a J 39200 from CKT 450 (BLK) at the connector PIN B and the chassis ground.

Does the DMM indicate continuity?

Go to Step 15

Go to Step 16

Replace the two-speed rear axle motor shift relay.

Is the replacement procedure complete?

System OK

Locate and repair the open in CKT 450 (BLK).

Is the repair complete?

System OK