IMPORTANT SERVICE
INFORMATION FOR:
 SERVICE MANAGER
 SERVICE ADVISOR
 TECHNICIAN
 PARTS DEPARTMENT
 WARRANTY PERSONNEL

BULLETIN NUMBER:
CB23-J-003
ISSUE DATE:
OCTOBER 2023
GROUP:
ENGINE

CUSTOMER SATISFACTION CAMPAIGN
TIRE SIZE REPROGRAMMING – ENGINE CONTROL
MODULE (ECM) AND MIMAMORI UNIT (MMU) (V2303)
AFFECTED VEHICLES
•

2022-2023MY F-Series Vehicles Equipped with RPO 5U5 Tire Size
255/70R22.5
INFORMATION

CONDITION
In some 2022-2023 MY Isuzu F-Series trucks equipped with RPO 5U5 Tire Size
255/70R22.5, a calibration error caused the affected vehicles to be built with an incorrect
tire size value. As a result, the speedometer will show a vehicle speed higher than the
actual vehicle speed while driving and the odometer will accumulate miles faster
(approximately 14% faster) than the “actual” or “True” vehicle miles. Additionally, mileage
data collected and stored in the Mimamori Unit (MMU) will be incorrect.
CORRECTION
Isuzu dealers will have the Cummins Engine Control Module (ECM) reprogrammed with
the correct tire size value and reprogram the MMU. This service will be provided free of
charge.
Isuzu is, by federal law, prohibited from adjusting the odometer to account for the
inaccurate mileage accumulated prior to the repair. To ensure the customer receives the
appropriate warranty coverage, Isuzu will also extend the ending mileage of the affected
truck’s emission warranty by 14,000 miles.
VEHICLES INVOLVED
Involved are certain 2022-2023 model year Isuzu F-Series vehicles equipped with RPO
5U5 Tire Size 255/70R22.5.
NOTE: It is not necessary to open a TAC case or generate a health report in order
to submit a warranty claim for this campaign.
NOTE: Dealers are to confirm vehicle eligibility prior to beginning repairs by using the
Isuzu Vehicle Information System (IVIS).

For dealers with involved vehicles, a report of involved vehicles containing the complete
vehicle identification number has been or will be provided. Dealers will not have a report
available if they have no involved vehicles currently assigned.
SERVICE PROCEDURE
1. Look up the VIN in the Isuzu Vehicle Information System (IVIS) and confirm the
vehicle is affected by this campaign.
2. Physically inspect the vehicle’s tires and record the tire’s size value. The tire size
should be 255/70R22.5.
a. If the value IS NOT 255/70R22.5, contact the Isuzu Technical Assistance
Center at 1-877-ISUZUCV (1-877-478-9828) for further assistance.
b. If the value IS 255/70R22.5, continue to the next step.
3. Contact the local Cummins Certified Service Facility to have the ECM reprogrammed
per the procedure below.
a. If you (the Isuzu dealer) are also a Cummins Certified Service Facility, this
procedure should be performed at your location, as you are the closest
Cummins Certified Service Facility.
b. If you (the Isuzu dealer) are not a Cummins Certified Service Facility, you
should arrange to have this procedure performed at the closest Cummins
Certified Service Facility; you can find the closest Cummins Certified
Service Facility on the web at https://www.cummins.com/locations.
4. Provide the “Procedure” section of this bulletin to the Cummins Certified Service
Facility to have a Cummins trained technician reprogram the ECM with the
correct Tire Size value settings using the Cummins INSITE tool.
NOTE: Once the Cummins procedure is completed, proceed to Step 17.
PROCEDURE (to be performed by a Cummins Certified Service location using
INSITE)
5. Using the Cummins INSITE tool (version 8.8.0.101 or later), from the Main
Screen, select Connect to ECM to establish communication with ECU, and
select Connect. (See Figure 1.)

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Figure 1

6. Navigate to “Features and Parameters”. (See Figure 2.)

Figure 2

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7. Navigate to “Vehicle Speed Source”. (See Figure 3.)

Figure 3

8. Navigate to “Tire Size”. (See Figure 4.)

Figure 4

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9. Change the Tire Size calibration from 491 revs/mile (current ECM Value) to:
563 revs/mile (low profile tire size value). (See Figure 5.)

Figure 5

10. Navigate to “File”, select “Sent To”, and select “ECM”. (See Figure 6.)

Figure 6

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11. Click OK to Confirm ECM Adjustment. (See Figure 7.)

Figure 7

12. Turn key switch OFF, and click OK. (See Figure 8.)

Figure 8

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13. Wait for the progress bar to complete. (See Figure 9.)

Figure 9

14. Turn key switch ON, and click OK. (See Figure 10.)

Figure 10

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15. The corrected value will show stored in the ECM. Confirm corrected “Tire Size”
ECM Value. (See Figure 11.)

Figure 11

16. Once the ECM has been reprogrammed, return the vehicle to the Isuzu dealer;
ISUZU DEALER should proceed to “MMU Reprogramming Via IDSS”.
MMU REPROGRAMMING VIA IDSS
17. Connect Isuzu Diagnostic Service System (IDSS) version 15.0.9 or later, to the
vehicle and click on the “Auto Detect” button and then select “Scan Tool”. (See
Figure 12.)

Figure 12

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18. Navigate to “Data Display” and “Mimamori ECU”. (See Figure 13.)

Figure 13

19. Use the drop-down arrow to select the “Configuration Data” datalist. (See Figure
14.)

Figure 14

20. Check the “Tire Size” value. (See Figure 15.)
a. If the value that was recorded in the inspection conducted in Step 2 IS
255/70R22.5 and the MMU value is 255/70R22.5, the tire size value is
CORRECT. No programming action is required. Proceed to “Apply the
Campaign Label”.
b. If the value that was recorded in the inspection conducted in Step 2 is
255/70R22.5 and the MMU is 11R22.5, the tire size value is INCORRECT.
Continue to the next step to reprogram the correct tire value.

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Figure 15

21. Navigate to “Controller Programming”. (See Figure 16.)

Figure 16

22. Select “Mimamori ECU”, then “Software and Calibrations” and then “Replace and
Reprogram Controller. (See Figure 17.)
IMPORTANT: DO NOT USE Update Calibration. This will NOT correct the EOL
settings in the MMU.

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Figure 17

23. Verify the VIN number matches the vehicle. If OK, click “Next”. (See Figure 18.)
NOTE: If the VIN does not match the vehicle, contact TAC for further assistance.

Figure 18

24. On this screen click “No”. You are not replacing the module so this step should
be ignored. (See Figure 19.)

Figure 19

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25. Confirm the VIN again. If OK, click “Next”. (See Figure 20.)
NOTE: If the VIN does not match the vehicle, contact TAC for further assistance.

Figure 20

26. On this screen click “Next”. You are not replacing the module so this step should
be ignored. (See Figure 21.)

Figure 21

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27. Click “Program EOL” and wait for the program event to finish. (See Figure 22.)

Figure 22

28. Turn the ignition “OFF” and click “Next”. (See Figure 23.)

Figure 23

29. Wait for the reset to finish. The screen will display “Programming complete!”
when finished. Then click “Exit”. (See Step 24.)

Figure 24

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30. Repeat Steps 17 through 20 and confirm the correct tire size value was
programmed.
31. Proceed to Applying the Campaign Label.
APPLYING THE CAMPAIGN LABEL
32. Using a ball-point pen, fill in a campaign label (Part No. 2-90028-700-0) with
Campaign Number V2303, Isuzu dealer code, and repair date.
33. Affix the campaign label onto the driver's side B-pillar.

CAMPAIGN CLAIM INFORMATION
Refer to the Isuzu ICS Claims Processing Manual for details on Campaign Claim
Submission. Submit only one claim as indicated below.
NOTE: It is not necessary to open a TAC case or generate a health report in order
to submit a warranty claim for this campaign.
Labor
Code

V2303

Description

Labor Hours

Sublet

ECM & MMU Reprogram
Customer Satisfaction Campaign

0.5*

ADD: Reprogram MMU

0.4

Cummins
Service Repair
Cost**

*Includes 0.1 hours for administrative allowance, coordination with Cummins Certified Service
Facility and campaign label installation.
** Use “Sublet C” for reimbursement of reprogramming expense from the Cummins location.
Dealers must attach the paid invoice, from the Cummins Certified Service Facility, to the claim
for reimbursement. If there are other expenses incurred during this process, please contact
your DSPM for additional direction on payment or reimbursement.

DEALER RESPONSIBILITY
All vehicles in dealers' possession and subject to this customer satisfaction campaign
must be held and repaired per the service procedure of this campaign bulletin before
customers take possession of these vehicles.
Customers who have recently purchased vehicles sold from your vehicle inventory, and
for which there is no customer information indicated on the dealer listing, are to be
contacted by the dealer. Arrangements are to be made to make the required correction
according to the instructions contained in this bulletin. A copy of the customer letter is
provided in this bulletin for your use in contacting customers. Program follow-up cards
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should not be used for this purpose, since the customer may not as yet have received the
notification letter.
In summary, whenever a vehicle subject to this customer satisfaction campaign enters
your vehicle inventory, or is in your dealership, you must take the steps necessary to be
sure the recall correction has been made before selling or releasing the vehicle.
OWNER NOTIFICATION
A sample of the customer satisfaction campaign letter that will be sent to owners of
affected vehicles already retailed in the United States is attached below.

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[SAMPLE OWNER LETTER – US]

CUSTOMER SATISFACTION CAMPAIGN
This notice applies to your vehicle,

OCTOBER 2023
Dear Customer,
The purpose of this notice is to inform you that Isuzu Commercial Truck of America, Inc. is
conducting a customer satisfaction campaign that affects 227 (two hundred and twenty-seven)
2022-2023 Model Year (MY) Isuzu F-Series trucks equipped with RPO 5U5 Tire Size
255/70R22.5. Your model year Isuzu F-Series, VIN , is involved in this
campaign.
WHAT IS THE CONDITION?
In some 2022-2023 MY Isuzu F-Series trucks equipped with RPO 5U5 Tire Size 255/70R22.5, a
calibration error caused the affected vehicles to be built with incorrect information about the tire
size. As a result of this error, your speedometer will show a vehicle speed higher than the actual
vehicle speed while driving and your odometer will accumulate miles faster (approximately 14%
faster) than the “actual” or “true” vehicle miles you have driven. Additionally, mileage data
collected and stored in the Mimamori Unit (MMU), is incorrect.
WHAT WE WILL DO
Your Isuzu dealer will have the Cummins ECM reprogrammed with the correct tire size value
(causing the speed to display correctly on the speedometer and the odometer to accumulate mileage
correctly going forward) and reprogram the MMU. This service will be provided free of charge.
Isuzu is, by federal law, prohibited from adjusting the odometer to account for the inaccurate
mileage accumulated prior to the repair. To ensure you receive the appropriate warranty coverage,
we will also extend the ending mileage of your truck’s emission warranty by 14,000 miles. Keep
this letter with your other important glove box literature for future reference.
WHAT YOU SHOULD DO
We recommend you contact your Isuzu dealer to schedule an appointment to bring your vehicle in
to have this service performed. Present this Owner Notification Letter at the time of your
appointment or refer to customer satisfaction campaign bulletin CB23-J-003. We estimate this
service may take approximately 60 minutes to perform, if your Isuzu dealer is also a Cummins
Certified Service Facility. However, if your dealer is not a Cummins Certified Service Facility and
depending on how appointments are scheduled and processed, additional time may be necessary.
To locate your nearest dealer please use the dealer locator on our website at www.isuzucv.com. If
you have questions or concerns, please contact our Customer Relations Department at 1-866-4419638.
We regret any inconvenience this action may cause you.
Sincerely,
Isuzu Commercial Truck of America, Inc.
Important: If you have sold or traded your Isuzu vehicle, please enter the owner's name and address, if known, on the attached "Change of
Information" postcard, tear off at both perforations, and drop it in the mail. Postage has already been paid. We will contact the new owner.

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