SB-10054667-8295

49-11

DEF Gauge Reading Incorrectly
> Constellation
Heritage
> 4700 Models

> 4800 Models
> 4900 Models

Western Star
Service Bulletin

> 5900 Models
> 6900 Models

Description of Revisions:This bulletin replaces the version dated
May 2013. Table 1 is revised to include more unit part numbers.

General Information
When a vehicle equipped with a diesel exhaust fluid (DEF) system sits for an extended period of time, the DEF
in the tank may crystallize around the float on the DEF level sending-unit tube and require cleaning. This crystallization may cause the float to stick on the tube. See Fig. 1. If the DEF level indicator displays an incorrect
level reading, complete the procedure below.

1

2
3

4

03/27/2012

f490469

1. Head Unit
2. Crystallized DEF

3. Float
4. Sending-Unit Tube

Fig. 1, Stuck DEF Float

IMPORTANT: When using an ohmmeter to measure the different resistance settings of the DEF level
sensor, it is important that the readings fall below the range chosen on the ohmmeter. The resistance
settings on the DEF sensor can range from approximately 68 ohms to 20,000 ohms. If the ohmmeter
is set on a 4k resistance setting, any reading over 4000 ohms will show "OL" on the meter. This is not
an open circuit issue but a mistake in choosing the range setting on the ohmmeter. To avoid this situation, set the ohmmeter resistance scale to one that is above the highest resistance reading
expected. For example, if the highest resistance reading will be 20,000 ohms, set the ohmmeter to
the 40k setting. As you work down to the lower resistance settings, switch the ohmmeter to a lower
range. When encountering an "OL" reading on the ohmmeter, always select a higher range to determine whether there is an open circuit or if it’s just a matter of being on too low of a range.

Western Star Service Bulletin, December 2013

Page 1

49-11

DEF Gauge Reading Incorrectly

Western Star
Service Bulletin

> Constellation
Heritage
> 4700 Models

> 4800 Models
> 4900 Models

> 5900 Models
> 6900 Models

Removal, Testing, and Installation
1. Check to see if there is DEF in the tank. If the tank is not empty, drain the tank.
On vehicles with A04-27943-000 and A04-27943-001 tanks, disconnect the DEF line from the DEF outlet
port at bottom of the tank, and let the DEF drain into the drain pan.
On vehicles with any other DEF header, use a siphon or invert the DEF tank after removal from the mounting brackets to empty the DEF from the tank.
2. Remove the tank from the vehicle. For instructions refer to Group 49 of the vehicle’s Workshop Manual.
3. Remove the DEF-level sending unit. For instructions refer to Group 49 of the vehicle’s Workshop Manual.
4. Clean the float and tube thoroughly with hot water, to restore free movement of the float on the tube.
5. Clean all DEF crystallization from the remainder of the unit with hot water.
6. Using a digital multimeter (DMM), test the sending unit resistance to make sure it is working properly. Refer
to Table 1 for DEF level sensor resistance.
6.1

Connect the ohm meter to the sending unit connector on the pins identified in Table 1.

NOTE: DEF level testing by moving the float with the sensor connected to the vehicle wiring is not
recommended because the display response time to any movement in the DEF sensor float can
take several minutes.
6.2

Position the float at the full, midpoint, and empty positions and compare the resistance to that shown
in Table 1.
If the readings are within approximately ±10 percent of those listed in Table 1, the unit is good. Go
to the next step.
If the readings are not within range, replace the sending unit with a new one.

7. Install the sending unit in the tank. For instructions refer to Group 49 of the vehicle’s Workshop Manual.
8. Install the tank. For instructions refer to Group 49 of the vehicle’s Workshop Manual.
9. Fill the tank with DEF.

Engine Type

DEF Level Sensor Resistance Measurement
Detroit
04-27881-000

Cummins

A04-27943-000
A04-27942-000
A04-27943-001

Part Number

A04-27445-000

04-30774-001
04-30798-001

04-30774-000
04-30798-000
Test at Sensor Connector Pins
NOTE: Pins are numbered left to right.
Resistance: Float at Top of Travel
Resistance: Float at Center of Travel
Resistance: Float at Bottom of Travel

1 and 2

1 and 4

1 and 4

1 and 2

~19800Ω
~2035Ω
~240Ω

~68Ω
~730Ω
~4812Ω

~68Ω
~1064Ω
~10890Ω

~68Ω
~742Ω
~4732Ω

Table 1, DEF Level Sensor Resistance Measurement

Page 2

Western Star Service Bulletin, December 2013

49-11

DEF Gauge Reading Incorrectly
> Constellation
Heritage
> 4700 Models

> 4800 Models
> 4900 Models

> 5900 Models
> 6900 Models

Western Star
Service Bulletin

Warranty
This procedure is warrantable only if the described condition exists and the repair is performed within the applicable base or extended coverage warranty period. If a failure is not found, this procedure is considered preventive and warranty does not apply.
Normal warranty applies. See Table 2 for QuickClaim damage code and labor allowance information. Refer to
this service bulletin by number at the beginning of the claim comments. See Table 3 for OWL VMRS codes and
labor allowance information. Enter this service bulletin number in the Service Bulletin # field.

Damage Code
234-000A07130

QuickClaim Damage Code and Labor Allowance
Description
DEF Level Sensor, R/R and Clean

SRT Code
234-5010A

Time: Hours
2.5

Table 2, QuickClaim Damage Code and Labor Allowance

Primary Failed Part
DEF Level Sensor
DEF Level Sensor

OWL VMRS Codes and Labor Allowance
Component
Cause Code SRT Code
Description
Code
043-007-156
37
234-5010A DEF Level Sensor, R/R and Clean
043-007-012
37
234-5010A DEF Level Sensor, R/R and Clean

Time: Hours
2.5
2.5

Table 3, OWL VMRS Codes and Labor Allowance

Western Star Service Bulletin, December 2013

Page 3