54-39

RX Module Fault Codes
> Constellation
> Heritage
4700 Models

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> 4900 Models

5900 Models
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Western Star
Service Bulletin

Description of Revisions: This bulletin replaces the version dated
October 2012. MID 37 is now used to transmit RX module fault
codes on EPA 2010 vehicles, and later. There are also additional
fault codes associated with EPA 2010 vehicles. The bulletin title is
also changed.

General Information
When ServiceLink or other diagnostic tools are used to monitor fault codes, there may be active faults with MID
37 that are nuisance faults. The RX module measures resistance or voltage of nine different vehicle sensors. It
then converts this data into SAE J1708/J1587 format, and broadcasts it over the vehicle J1708/J1587 databus.
The following sensor inputs may be connected to the RX module:
• pyrometer thermocouple;
• ammeter shunt;
• fuel level sensor;
• up to six other temperature sensors.
The RX module can sense an open circuit or a disconnected sensor for each input except the ammeter shunt.
The RX module reports these fault conditions on the J1587 databus. See Table 1.

NOTE: Some vehicles do not use all nine sensors. For sensor inputs that are not used on the vehicle,
open-circuit fault codes for those inputs should be treated as nuisance faults. For sensor inputs that
are used on the vehicle, open-circuit fault codes for those inputs should be treated as actual faults to
be repaired as necessary.
IMPORTANT: In 2010, MID 37 replaced MID 41 to transmit RX module fault codes.
Use Table 1 to identify J1587 fault codes reported by the RX module for EPA 2007 vehicles, and earlier.
Use Table 2 to identify J1587 fault codes reported by the RX module for EPA 2010 vehicles, and later.

J1587
MID
41
41
41
41
41
41
41
41

RX Module Fault Codes, EPA 2007 and Earlier
Fault Code
Fault Code Description
PID
FMI
077
05
Forward-Rear Axle Temperature Sensor — Open Circuit
078
05
Rear-Rear Axle Temperature Sensor — Open Circuit
096
05
Fuel Level Sensor — Open Circuit
120
05
Brake Saver Temperature Sensor — Open Circuit
173
05
Pyrometer Thermocouple — Open Circuit*
177
05
Transmission #1 Oil Temperature Sensor — Open Circuit
373
05
Center-Rear Axle Temperature Sensor — Open Circuit
418
05
Transmission #2 Temperature Sensor — Open Circuit

* This fault will only occur after the pyrometer voltage is below the minimum (or open circuit) for 4 minutes after
the ignition is turned on. This is to avoid faults when the exhaust temperature is low right after the engine is started.

Table 1, RX Module Fault Codes, EPA 2007 and Earlier

Western Star Service Bulletin, June 2013

Page 1

54-39

RX Module Fault Codes

Western Star
Service Bulletin

J1587
MID
37
37
37
37
37
37
37
37
37
37

> Constellation
> Heritage
4700 Models

4800 Models
> 4900 Models

5900 Models
> 6900 Models

RX Module Fault Codes, EPA 2010 and Later
Fault Code
Fault Code Description
PID
FMI
077
05
Forward-Rear Axle Temperature Sensor — Open Circuit
078
05
Rear-Rear Axle Temperature Sensor — Open Circuit
096
05
Fuel Level Sensor — Open Circuit
114
05
Ammeter — Open Circuit
120
05
Brake Saver Temperature Sensor — Open Circuit
171
05
Outside Air Temperature — Open Circuit
173
05
Pyrometer Thermocouple — Open Circuit*
177
05
Transmission #1 Oil Temperature Sensor — Open Circuit
373
05
Center-Rear Axle Temperature Sensor — Open Circuit
418
05
Transmission #2 Temperature Sensor — Open Circuit

* This fault will only occur after the pyrometer voltage is below the minimum (or open circuit) for 4 minutes after
the ignition is turned on. This is to avoid faults when the exhaust temperature is low right after the engine is started.

Table 2, RX Module Fault Codes, EPA 2010 and Later

Warranty
This is an information bulletin only; warranty does not apply.

Page 2

Western Star Service Bulletin, June 2013