49-5

DEF Gauge Reading Incorrectly

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

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

General Information
When filing a warranty claim in OWL for this service bulletin, add the letter "T" to the end of the SB number. In
this case, "49-5T".
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

1. Check to see if there is DEF in the tank. If the tank is not empty, drain the tank.
On vehicles with a 6-gallon DEF tank, disconnect the DEF line from the DEF outlet port and let the DEF
drain into the drain pan.
On vehicles with a 13- or 23-gallon DEF tank, use a siphon 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.

Thomas Built Buses Service Bulletin, May 2013

Page 1

49-5

DEF Gauge Reading Incorrectly

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

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.

DEF Level Sensor Resistance Measurement
Detroit
Cummins
A04-27445-000
A04-28046-000
Part Number
All
A04-27942-000
A04-28402-000
Test at Sensor Connector Pins
1 and 2
1 and 4
Resistance with Float at Top of Travel
~19800Ω
~70Ω
~112Ω
Resistance with Float at Center of Travel
~2035Ω
~730Ω
~750Ω
Resistance with Float at Bottom of Travel
~240Ω
~4810Ω
~4812Ω
Engine Type

Table 1, DEF Level Sensor Resistance Measurement

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.

Page 2

Thomas Built Buses Service Bulletin, May 2013

49-5

DEF Gauge Reading Incorrectly

Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

When filing warranty claims in OWL for this service bulletin, enter 49-5T as the service bulletin number.

Damage Code
234-000A07130

SRT Code
234-5010A

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

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

Thomas Built Buses Service Bulletin, May 2013

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