Gentech DEF Coolant-Flow Solenoid, Testing and
Replacement

49-4
Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

Description of Revisions: This bulletin replaces the version dated
September 2012. Any Gentech DEF coolant-flow control solenoid
related fault codes are now acceptable. The "Solenoid Test" instructions are also clarified.

General Information
NOTE: This bulletin pertains to vehicles with Cummins engines and aftertreatment systems only.
NOTE: The test procedure should be performed with the header unit installed in the DEF tank.
The Gentech diesel exhaust fluid (DEF) coolant-flow-control solenoid is an electric 12V solenoid that controls
the flow of coolant through stainless steel tubes in the DEF tank. The solenoid is checked every time the truck
is started and is used when the DEF temperature drops to its freezing point, 12°F (-11°C) or below. The command is controlled by the Cummins engine controller. Several different fault codes may indicate a problem with
the DEF tank temperature data. See Table 1 for the most common examples. If any Gentech DEF coolant-flow
control solenoid related fault codes are shown, perform the following test to determine if the solenoid valve functions correctly.

Fault Code
1679
1683
1684

Gentech DEF Coolant-Flow-Solenoid, Common Fault Codes (Typical)
Description
Aftertreatment DEF tank temperature – data erratic, intermittent, or incorrect.
Aftertreatment DEF tank heater – voltage above normal, or shorted to high source.
Aftertreatment DEF tank heater – voltage below normal, or shorted to low source.
Table 1, Gentech DEF Coolant-Flow-Solenoid, Common Fault Codes (Typical)

If the solenoid valve is functioning correctly, test the rest of the system for the problem.
If the solenoid valve is not functioning correctly, replace the solenoid valve assembly only. Do not replace the
complete header.

Solenoid Test
NOTE: Wear protective gloves when working on the DEF system to protect from crystallized DEF.
1. Park the vehicle on a level surface, shut down the engine, and set the parking brakes. Chock the tires.

IMPORTANT: Gentech changed the design of the coolant flow control solenoid in March 2011. There
are two different solenoids with the same part number but different resistance values. Refer to Fig. 1
and Fig. 2 to see the differences in the solenoid housings. The tag on the solenoid will say, "7W" or
"10W".
2. Determine which style of solenoid is installed on the vehicle. See Fig. 1 and Fig. 2.
3. Disconnect the 2-pin solenoid connector from the harness.
4. Measure the resistance of the solenoid. The solenoid resistance should be 20±1 Ω for the 7-watt unit, or
13.5±0.7 Ω for the 10-watt unit. Wiggle the solenoid pigtail to test for an intermittent condition.
If the reading is within specification, remove the Phillips screw from the solenoid, separate the two parts of
the solenoid, and check for corrosion on or around the solenoid terminals. See Fig. 3.
If the solenoid resistance is out of range, or if there is corrosion, replace the solenoid valve assembly only.
Do not replace the complete header.

Thomas Built Buses Service Bulletin, June 2013

Page 1

49-4

Gentech DEF Coolant-Flow Solenoid, Testing and
Replacement

Thomas Built Buses
Service Bulletin

03/22/2012

> Saf-T-Liner C2

f490466

Fig. 1, 7-Watt Solenoid Valve ( 20±1 Ω)

03/22/2012

f490465

Fig. 2, 10-Watt Solenoid Valve (13.5±0.7 Ω)

If the solenoid resistance is not out of range, or if there is no corrosion, troubleshoot the rest of the system.

Solenoid Valve Assembly Replacement
Refer to Fig. 4 for this procedure.
1. Park the vehicle on a level surface, shut down the engine, and set the parking brakes. Chock the tires.
2. Using hose-pinch pliers, pinch off the rubber coolant lines connected to the DEF tank.
3. Remove the DEF tank cover, if equipped.
4. Place a catch pan under the DEF tank to catch any lost coolant.
5. Remove the retaining clip, and disconnect the coolant line at the solenoid valve.
6. Disconnect the solenoid pigtail connector.
7. Remove the retaining clip.
8. Rotate the solenoid valve out of the retainer, and pull it from the header.
9. Push the the new solenoid valve into the header, and rotate it into the retainer.
10. Install the retaining clip.
11. Connect the wire harness.
12. Connect the coolant lines at the valve.
13. Remove the pinch pliers from the coolant lines.
14. Install the DEF tank cover, if equipped.
15. Check the coolant level, and add coolant as needed.

Page 2

Thomas Built Buses Service Bulletin, June 2013

Gentech DEF Coolant-Flow Solenoid, Testing and
Replacement

49-4
Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

3
7

3

4

2

2
5
11/14/2011

6

f490462

Remove the pigtail cable and check this area for
corrosion.

1

Fig. 3, Checking for Corrosion
08/08/2012

f490460a

Test the solenoid resistance at the 2-pin connector.
1. DEF Line Connections (lines not shown for clarity)
2. Coolant Line
3. Retainer, Solenoid Valve
4. 2-Pin Connector, Solenoid
5. Solenoid Valve
6. Retaining Clip, Solenoid Valve to Header
7. Phillips Screw
Fig. 4, DEF Coolant Flow Solenoid Installation (DEF
lines not shown for clarity)

Parts
Parts are available through the PDC. See Table 2 for part numbers.

Part Number
04-28039-000
04-28039-001

Replacement DEF Solenoid Valves
Description
Where Used
10-, 11.5-, 13- and 23-Gallon
Solenoid Valve, LH
Tanks
Solenoid Valve, RH
6-Gallon Tank
Table 2, Replacement DEF Solenoid Valves

Thomas Built Buses Service Bulletin, June 2013

Page 3

Gentech DEF Coolant-Flow Solenoid, Testing and
Replacement

49-4
Thomas Built Buses
Service Bulletin

> Saf-T-Liner C2

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 3 for QuickClaim damage code and labor allowance information. Refer to
this service bulletin by number at the beginning of the claim comments. See Table 4 for OWL VMRS codes and
labor allowance information. Enter this service bulletin number in the Service Bulletin # field.

Damage Code
23U-007-059
23U-007-059

SRT Code
234-5005B
234-5005A

QuickClaim Damage Code and Labor Allowance
Description
DEF, Coolant Flow, Solenoid, Test
DEF, Coolant Flow, Solenoid/Valve, R/R

Time: Hours
0.2
0.8

Table 3, QuickClaim Damage Code and Labor Allowance

Primary Failed Part
04-28039-000 or 0428039-001
04-28039-000 or 0428039-001

OWL VMRS Codes and Labor Allowance
Component
Cause Code SRT Code
Description
Code

Time: Hours

043-007-018

12

234-5005B DEF, Coolant Flow, Solenoid, Test

0.2

043-007-018

12

234-5005A DEF, Coolant Flow, Solenoid/Valve, R/R

0.8

Table 4, OWL VMRS Codes and Labor Allowance

Page 4

Thomas Built Buses Service Bulletin, June 2013