Mach 307
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- Thread starter
- #1
TL;DR / Solution
For 2021+ S550 Mustangs with the wired rear buckle sensors, this allows the rear buckle/receptacle assemblies to be completely removed when installing a rear seat delete instead of leaving the wired buckles plugged in to prevent DTCs.
Using FORScan, change the following values:
IPC 720-02-02:
xxx4 xxxx → xxx0 xxxx
RCM 737-02-01:
xxxx xxxx 7xxx → xxxx xxxx 1xxx
Change only those identified values, not the entire As-Built lines.
Then:
1. Power the car down.
2. Unplug both rear buckle sensors.
3. Power the car back up.
4. Clear any existing DTCs.
5. Perform a fresh DTC scan.
Tested successfully on my 2022 Mach 1: both rear buckle sensors unplugged with no DTCs.
You can now fully remove the rear female buckle/receptacle assemblies for the rear seat delete.
Back up your original As-Built before making any changes.
——————————————————————
2021+ Mustang Mach 1 / GT500 Rear Seat Delete — Possible FORScan Solution
TL;DR
Based on a comparison of complete factory As-Built data from 33 S550 Mustangs, the proposed 2021+ rear-seat-delete configuration changes are:
IPC 720-02-02
xxx4 xxxx -> xxx0 xxxx
RCM 737-02-01
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
For the IPC, change only the indicated 4 to 0 and let FORScan calculate the checksum.
For the RCM, the complete factory target value was identical across the entire dataset, so the full factory RSD value can also be used:
C768 ED3B 7008 -> C768 ED3B 10A8
There were no exceptions to the relevant pattern in the 33-car sample, and I did not find another universal As-Built setting that consistently separated the 2021+ four-seat cars from the factory RSD/pre-2021 configuration.
Do not copy any other As-Built values from a donor car.
Background
I’ve been researching the rear seat-belt monitoring issue that comes up when installing a rear seat delete in 2021+ S550 Mustangs.
On these cars, removing and unplugging the rear buckle sensors can cause a rear seat-belt system warning. The workaround people have generally used has been to leave the rear buckle electronics connected and hide them underneath the rear seat delete.
I wanted to figure out how Ford handled this on cars that actually came with a rear seat delete from the factory.
I started with Ford’s own Mustang workshop/service information instead of randomly searching As-Built values. Ford identifies the IPC as module 720 and the RCM as module 737, and BeltMinder/seat-belt reminder configuration functions are associated with those modules.
The service information does not specifically state that rear seat delete coding is located at 720-02-02 and 737-02-01. What it did was narrow down which modules were relevant. The exact As-Built addresses and values were then isolated by comparing factory production data.
Dataset
I collected and compared the complete factory As-Built files from 33 S550 Mustangs spanning 2019–2023.
18 Mach 1s from 2021–2023:
12 four-seat cars
6 factory rear-seat-delete cars
The 12 four-seat Mach 1 controls included 8 Recaro cars and 4 comfort-seat cars, with manual and automatic transmissions and both Handling Package and non-Handling Package configurations represented.
9 GT500s from 2020–2022:
3 Recaro four-seat GT500s
3 comfort-seat four-seat GT500s
3 factory Carbon Fiber Track Package cars with the rear seat delete
That gave me one Recaro four-seat GT500, one comfort-seat four-seat GT500, and one CFTP/RSD GT500 for each of the 2020, 2021, and 2022 model years.
6 GT350s from 2019–2020:
2 Recaro four-seat GT350s
2 comfort-seat four-seat GT350s
2 factory GT350Rs with the rear seat delete
That gave me one Recaro GT350, one comfort-seat GT350, and one GT350R for both 2019 and 2020.
In total, the dataset contains 21 four-seat cars and 12 factory rear-seat-delete cars if the Mach 1 RSD, GT500 CFTP, and GT350R groups are combined.
The older GT350s and 2020 GT500s were especially useful because they provided controls from before the newer 2021+ rear seat-belt monitoring configuration.
How the parameters were found
I compared the complete As-Built files rather than only looking at a couple of suspected restraint-related addresses.
Across the dataset, the universal 2021+ four-seat versus factory-RSD/pre-2021 difference consistently came down to two locations.
FIRST:
IPC 720-02-02
2021+ four-seat configuration:
xxx4 xxxx
Factory RSD / earlier configuration:
xxx0 xxxx
Universal change:
xxx4 xxxx -> xxx0 xxxx
Only the indicated 4 changes to 0.
The rest of the IPC line varies depending on the individual vehicle’s equipment, so I would not recommend copying an entire IPC line from another car.
Instead, change only the universal 4 to 0 and let FORScan calculate the proper checksum for that particular vehicle.
SECOND:
RCM 737-02-01
2021+ four-seat configuration:
xxxx xxxx 7xxx
Factory RSD / earlier configuration:
xxxx xxxx 1xxx
Universal change:
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
The actual configuration change is the indicated 7 changing to 1.
The RCM is different from the IPC because the complete 737-02-01 line was invariant throughout the 33-car dataset.
It appeared in only two forms:
2021+ four-seat:
C768 ED3B 7008
Factory RSD / pre-2021 state:
C768 ED3B 10A8
Every applicable 2021+ four-seat car in the dataset used C768 ED3B 7008.
Every applicable factory-RSD or pre-2021 car used C768 ED3B 10A8.
There were no exceptions.
Because of that, the complete factory RSD RCM value can reasonably be copied directly:
C768 ED3B 7008 -> C768 ED3B 10A8
You could alternatively change only the 7 to 1 and allow FORScan to recalculate the checksum, but unlike the IPC, the complete RCM target value is known and was identical across every applicable car in the dataset.
Production pattern
The production pattern was extremely consistent.
All of the 2021+ four-seat Mach 1 and GT500 examples used the 4 / 7 configuration.
All of the 2021+ factory-RSD Mach 1 and GT500 examples used the 0 / 1 configuration.
The 2019–2020 cars also used the 0 / 1 state regardless of whether they physically had a rear seat.
That is important because it suggests these values relate to Ford’s newer 2021+ rear-belt-monitoring architecture rather than simply meaning “rear seat installed” or “rear seat deleted.”
The GT500 comparison is especially useful.
For 2020, before the newer monitoring configuration appeared in the dataset, both the four-seat GT500s and CFTP/RSD GT500 used the older 0 / 1 configuration.
Beginning in 2021, the four-seat GT500s switched to the 4 / 7 configuration while the factory CFTP/RSD cars remained at 0 / 1.
The exact same split repeated in 2022.
The Mach 1 data reproduced that same four-seat-versus-RSD pattern across 2021, 2022, and 2023.
Other As-Built differences
I found other differences between regular GT500s and CFTP cars and between GT350s and GT350Rs.
However, those differences existed independently of the 2021 rear-belt-monitoring transition and were not reproduced across the factory Mach 1 rear-seat-delete cars.
Those appear to be CFTP/GT350R package-specific configuration rather than universal rear-seat-delete coding.
I would not change any of those values.
After comparing the complete As-Built files, I did not find a third universal setting that consistently separated the 2021+ four-seat cars from the factory RSD/pre-2021 configuration.
My 2022 Mach 1 example
IPC 720-02-02
Current:
4884 8C83
Universal change:
4 -> 0
Expected after FORScan checksum update:
4880 8C7F
RCM 737-02-01
Current:
C768 ED3B 7008
Universal change:
7 -> 1
Factory target value:
C768 ED3B 10A8
Proposed FORScan RSD changes
FIRST:
IPC 720-02-02
xxx4 xxxx -> xxx0 xxxx
Change only the indicated 4 to 0 and let FORScan calculate the checksum.
SECOND:
RCM 737-02-01
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
Either change only the indicated 7 to 1 and allow FORScan to calculate the checksum, or use the complete factory target:
C768 ED3B 10A8
Do not copy any other As-Built lines or values from a donor vehicle.
Why I think these are the relevant settings
Ford’s service information points to the IPC and RCM as the modules involved with BeltMinder/seat-belt reminder configuration, while the factory As-Built comparison isolated the exact addresses and bits within those modules.
The service information supports the module-level theory; the 33-car production dataset provides the exact As-Built evidence.
Important disclaimer
This is not an official Ford retrofit procedure.
The factory-data correlation is extremely strong, but I have not yet completed real-world validation on a converted car.
Anyone testing this should save the original IPC and RCM As-Built files first and make only the two changes listed above.
After writing the values:
Key-cycle the vehicle.
Re-read 720-02-02 and 737-02-01 to confirm the stored values.
Perform a complete DTC scan.
Verify normal restraint-system and instrument-cluster operation.
For the first test, I would leave the rear buckle sensors connected.
If everything remains clean, the more important second test would be disconnecting the rear buckle sensors and confirming that no rear-belt-monitor or restraint-system faults return.
If anyone tests this, please post:
Vehicle/model year
Whether the car originally had four seats or factory RSD
Original 720-02-02 value
New 720-02-02 value after FORScan writes it
Original 737-02-01 value
New 737-02-01 value after FORScan writes it
Any DTCs immediately after programming
Whether the DTCs clear and remain gone
Whether the rear buckle sensors were connected or disconnected
Whether any rear BeltMinder warning appears afterward
If this works the way the factory data suggests, it could eliminate the need to retain the rear buckle sensors underneath an aftermarket/Ford Performance rear seat delete.
For 2021+ S550 Mustangs with the wired rear buckle sensors, this allows the rear buckle/receptacle assemblies to be completely removed when installing a rear seat delete instead of leaving the wired buckles plugged in to prevent DTCs.
Using FORScan, change the following values:
IPC 720-02-02:
xxx4 xxxx → xxx0 xxxx
RCM 737-02-01:
xxxx xxxx 7xxx → xxxx xxxx 1xxx
Change only those identified values, not the entire As-Built lines.
Then:
1. Power the car down.
2. Unplug both rear buckle sensors.
3. Power the car back up.
4. Clear any existing DTCs.
5. Perform a fresh DTC scan.
Tested successfully on my 2022 Mach 1: both rear buckle sensors unplugged with no DTCs.
You can now fully remove the rear female buckle/receptacle assemblies for the rear seat delete.
Back up your original As-Built before making any changes.
——————————————————————
2021+ Mustang Mach 1 / GT500 Rear Seat Delete — Possible FORScan Solution
TL;DR
Based on a comparison of complete factory As-Built data from 33 S550 Mustangs, the proposed 2021+ rear-seat-delete configuration changes are:
IPC 720-02-02
xxx4 xxxx -> xxx0 xxxx
RCM 737-02-01
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
For the IPC, change only the indicated 4 to 0 and let FORScan calculate the checksum.
For the RCM, the complete factory target value was identical across the entire dataset, so the full factory RSD value can also be used:
C768 ED3B 7008 -> C768 ED3B 10A8
There were no exceptions to the relevant pattern in the 33-car sample, and I did not find another universal As-Built setting that consistently separated the 2021+ four-seat cars from the factory RSD/pre-2021 configuration.
Do not copy any other As-Built values from a donor car.
Background
I’ve been researching the rear seat-belt monitoring issue that comes up when installing a rear seat delete in 2021+ S550 Mustangs.
On these cars, removing and unplugging the rear buckle sensors can cause a rear seat-belt system warning. The workaround people have generally used has been to leave the rear buckle electronics connected and hide them underneath the rear seat delete.
I wanted to figure out how Ford handled this on cars that actually came with a rear seat delete from the factory.
I started with Ford’s own Mustang workshop/service information instead of randomly searching As-Built values. Ford identifies the IPC as module 720 and the RCM as module 737, and BeltMinder/seat-belt reminder configuration functions are associated with those modules.
The service information does not specifically state that rear seat delete coding is located at 720-02-02 and 737-02-01. What it did was narrow down which modules were relevant. The exact As-Built addresses and values were then isolated by comparing factory production data.
Dataset
I collected and compared the complete factory As-Built files from 33 S550 Mustangs spanning 2019–2023.
18 Mach 1s from 2021–2023:
12 four-seat cars
6 factory rear-seat-delete cars
The 12 four-seat Mach 1 controls included 8 Recaro cars and 4 comfort-seat cars, with manual and automatic transmissions and both Handling Package and non-Handling Package configurations represented.
9 GT500s from 2020–2022:
3 Recaro four-seat GT500s
3 comfort-seat four-seat GT500s
3 factory Carbon Fiber Track Package cars with the rear seat delete
That gave me one Recaro four-seat GT500, one comfort-seat four-seat GT500, and one CFTP/RSD GT500 for each of the 2020, 2021, and 2022 model years.
6 GT350s from 2019–2020:
2 Recaro four-seat GT350s
2 comfort-seat four-seat GT350s
2 factory GT350Rs with the rear seat delete
That gave me one Recaro GT350, one comfort-seat GT350, and one GT350R for both 2019 and 2020.
In total, the dataset contains 21 four-seat cars and 12 factory rear-seat-delete cars if the Mach 1 RSD, GT500 CFTP, and GT350R groups are combined.
The older GT350s and 2020 GT500s were especially useful because they provided controls from before the newer 2021+ rear seat-belt monitoring configuration.
How the parameters were found
I compared the complete As-Built files rather than only looking at a couple of suspected restraint-related addresses.
Across the dataset, the universal 2021+ four-seat versus factory-RSD/pre-2021 difference consistently came down to two locations.
FIRST:
IPC 720-02-02
2021+ four-seat configuration:
xxx4 xxxx
Factory RSD / earlier configuration:
xxx0 xxxx
Universal change:
xxx4 xxxx -> xxx0 xxxx
Only the indicated 4 changes to 0.
The rest of the IPC line varies depending on the individual vehicle’s equipment, so I would not recommend copying an entire IPC line from another car.
Instead, change only the universal 4 to 0 and let FORScan calculate the proper checksum for that particular vehicle.
SECOND:
RCM 737-02-01
2021+ four-seat configuration:
xxxx xxxx 7xxx
Factory RSD / earlier configuration:
xxxx xxxx 1xxx
Universal change:
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
The actual configuration change is the indicated 7 changing to 1.
The RCM is different from the IPC because the complete 737-02-01 line was invariant throughout the 33-car dataset.
It appeared in only two forms:
2021+ four-seat:
C768 ED3B 7008
Factory RSD / pre-2021 state:
C768 ED3B 10A8
Every applicable 2021+ four-seat car in the dataset used C768 ED3B 7008.
Every applicable factory-RSD or pre-2021 car used C768 ED3B 10A8.
There were no exceptions.
Because of that, the complete factory RSD RCM value can reasonably be copied directly:
C768 ED3B 7008 -> C768 ED3B 10A8
You could alternatively change only the 7 to 1 and allow FORScan to recalculate the checksum, but unlike the IPC, the complete RCM target value is known and was identical across every applicable car in the dataset.
Production pattern
The production pattern was extremely consistent.
All of the 2021+ four-seat Mach 1 and GT500 examples used the 4 / 7 configuration.
All of the 2021+ factory-RSD Mach 1 and GT500 examples used the 0 / 1 configuration.
The 2019–2020 cars also used the 0 / 1 state regardless of whether they physically had a rear seat.
That is important because it suggests these values relate to Ford’s newer 2021+ rear-belt-monitoring architecture rather than simply meaning “rear seat installed” or “rear seat deleted.”
The GT500 comparison is especially useful.
For 2020, before the newer monitoring configuration appeared in the dataset, both the four-seat GT500s and CFTP/RSD GT500 used the older 0 / 1 configuration.
Beginning in 2021, the four-seat GT500s switched to the 4 / 7 configuration while the factory CFTP/RSD cars remained at 0 / 1.
The exact same split repeated in 2022.
The Mach 1 data reproduced that same four-seat-versus-RSD pattern across 2021, 2022, and 2023.
Other As-Built differences
I found other differences between regular GT500s and CFTP cars and between GT350s and GT350Rs.
However, those differences existed independently of the 2021 rear-belt-monitoring transition and were not reproduced across the factory Mach 1 rear-seat-delete cars.
Those appear to be CFTP/GT350R package-specific configuration rather than universal rear-seat-delete coding.
I would not change any of those values.
After comparing the complete As-Built files, I did not find a third universal setting that consistently separated the 2021+ four-seat cars from the factory RSD/pre-2021 configuration.
My 2022 Mach 1 example
IPC 720-02-02
Current:
4884 8C83
Universal change:
4 -> 0
Expected after FORScan checksum update:
4880 8C7F
RCM 737-02-01
Current:
C768 ED3B 7008
Universal change:
7 -> 1
Factory target value:
C768 ED3B 10A8
Proposed FORScan RSD changes
FIRST:
IPC 720-02-02
xxx4 xxxx -> xxx0 xxxx
Change only the indicated 4 to 0 and let FORScan calculate the checksum.
SECOND:
RCM 737-02-01
xxxx xxxx 7xxx -> xxxx xxxx 1xxx
Either change only the indicated 7 to 1 and allow FORScan to calculate the checksum, or use the complete factory target:
C768 ED3B 10A8
Do not copy any other As-Built lines or values from a donor vehicle.
Why I think these are the relevant settings
Ford’s service information points to the IPC and RCM as the modules involved with BeltMinder/seat-belt reminder configuration, while the factory As-Built comparison isolated the exact addresses and bits within those modules.
The service information supports the module-level theory; the 33-car production dataset provides the exact As-Built evidence.
Important disclaimer
This is not an official Ford retrofit procedure.
The factory-data correlation is extremely strong, but I have not yet completed real-world validation on a converted car.
Anyone testing this should save the original IPC and RCM As-Built files first and make only the two changes listed above.
After writing the values:
Key-cycle the vehicle.
Re-read 720-02-02 and 737-02-01 to confirm the stored values.
Perform a complete DTC scan.
Verify normal restraint-system and instrument-cluster operation.
For the first test, I would leave the rear buckle sensors connected.
If everything remains clean, the more important second test would be disconnecting the rear buckle sensors and confirming that no rear-belt-monitor or restraint-system faults return.
If anyone tests this, please post:
Vehicle/model year
Whether the car originally had four seats or factory RSD
Original 720-02-02 value
New 720-02-02 value after FORScan writes it
Original 737-02-01 value
New 737-02-01 value after FORScan writes it
Any DTCs immediately after programming
Whether the DTCs clear and remain gone
Whether the rear buckle sensors were connected or disconnected
Whether any rear BeltMinder warning appears afterward
If this works the way the factory data suggests, it could eliminate the need to retain the rear buckle sensors underneath an aftermarket/Ford Performance rear seat delete.
Sponsored
Last edited:
