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How do I decode the odometer "N" message in the RIH Log?
N message decoded in RIH Log
Fleetwatch FMS · RIH Log Troubleshooting
Decoding the JX Odometer “N Message”
The RIH log shows the odometer reported by the vehicle’s JX module as an N Message. The odometer value is in hexadecimal. This guide shows how to find it in the message and convert it to miles.
Example N Message
Each colored section is explained in the table below.
J3D5D4DN00000003298000F504C7E124000000000000000000000000000000060439080613*8000F70440A3020000000000000000000000000000060439080613*36<-
| # | Value | Meaning |
|---|---|---|
| 1 | 3D5D4D | Tag ID of the vehicle’s module. |
| 2 | N | Marks this as an N message. |
| 3 | 0000 | Division. |
| 4 | 000329 | Vehicle number. |
| 5 | 80 | Message ID (MID). Hex 80 = decimal 128, the ID for the engine control module (ECM). |
| 6 | F5 | Parameter ID (PID). Hex F5 = decimal 245. PID 245 is Total Vehicle Distance, which is the odometer. |
| 7 | 04 | Number of data bytes that follow. 4 bytes = 8 hex characters. |
| 8 | C7E12400 | The odometer value, in hex. Decode it using the steps below. |
Decoding the Odometer
| 1 |
Take the 8 characters after the 04.
C7 E1 24 00
|
| 2 |
Reverse the order of the pairs. Start from the last pair and work backward. Keep the two characters in each pair together.
00 24 E1 C7
|
| 3 |
Convert hex to decimal. Enter 0024E1C7 into a hex-to-decimal calculator.
0024E1C7 (hex) = 2,417,095 (decimal)
|
| 4 |
Convert to miles. PID 245 counts in steps of 0.1 mile, so multiply by 0.1 (or move the decimal point one place to the left).
2,417,095 × 0.1 = 241,709.5 miles
|
Odometer reported by vehicle 000329
241,709.5 miles
(about 388,994 km)
Why reverse the pairs?
The vehicle’s data bus (J1587/J1708) sends multi-byte values least significant byte first. Reversing the pairs puts the bytes back in normal reading order before converting. Reverse whole pairs only. Don’t reverse the individual characters: C7 stays C7, not 7C.
Using the Windows Calculator
| 1 | Open Calculator, click the menu (☰), and choose Programmer. |
| 2 | Click HEX, then type the reversed value (for example, 24E1C7). Leading zeros can be left off. |
| 3 | Read the decimal result on the DEC line, then multiply by 0.1 for miles. |
Bonus: Engine Hours in the Same Message
The section after the * follows the same pattern, but with a different PID:
8000F70440A3020000000000…
| PID | Hex F7 = decimal 247, Total Engine Hours |
| Data bytes reversed | 40 A3 02 00 → 00 02 A3 40 |
| Hex to decimal | 0002A340 = 172,864 |
| Convert (0.05 hour per count) | 172,864 × 0.05 = 8,643.2 engine hours |
Quick reference
| Hex | Decimal | Meaning | Multiply by |
|---|---|---|---|
| MID 80 | 128 | Engine control module (ECM) | — |
| PID F5 | 245 | Total Vehicle Distance (odometer) | 0.1 (miles) |
| PID F7 | 247 | Total Engine Hours | 0.05 (hours) |
Questions about RIH logs or odometer readings? Reach out to Fleetwatch Support.