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2/28/22, 1:02 PM
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DEF Level (UQLS) Sensor Troubleshooting Guide US17+OBD16 Emissions and Newer
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Internal Content
Overview
The Urea Quality Level Sensor (UQLS) is a smart sensor that is located in
the top of the Urea (DEF) Tank, commonly referred to as the DEF Level
Sensor or Combined Tank Unit. This smart sensor has Urea Quality,
Level, and Temperature all integrated into it as one unit and reports on
the DL7 (J1939-7) Datalink. This sensor is responsible for sending all the
urea information to the Aftertreatment Control Module (ACM) and
Engine Control Module (ECM).
Diagnosis and Repair
Perform a DTC Readout and Review Codes
If any of the codes in yellow below appear on the Readout in Active
or Confirmed status: Continue to the diagnostic steps in the following
section.
DTC
DTC Description
P203A13
P203C00
Reductant Tank Temperature Sensor, Circuit
Range/Performance
Reductant Level Sensor "A", Open Circuit
Aftertreatment Reagent Level, Short Circuit Low
P206A13
P206C00
Reductant Quality Sensor, Open Circuit
Reductant Quality Sensor, Short Circuit Low
P206B64
P205A13
Reductant Quality Sensor Range/Performance
Reductant Tank Temperature Sensor, Open Circuit
P205B64
P205C00 Aftertreatment Reagent Tank Temperature, Short Circuit Low
; Live UI
DO NOT REPLACE the DEF Level Sensor for any of the codes
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in green below: DO NOT proceed with the diagnostics steps in this
solution. None of these codes immediately indicate a failed DEF Level
Sensor. Use the table in conjunction with PTT’s Guided Diagnostics to
find the root cause.
DTC
DTC Description
P203F00 Reductant Level
Low
Aftertreatment
P203B00 Reagent Level
Warning
Lost
Communication
U02A200
with Reductant
Quality Module
Probable Source
Commonly low DEF quantity or
level sensor float in DEF tank stuck
System fault. Follow Guided Diagnostics.
Commonly a wiring harness or connection
issue.
Reductant
DEF tank temp above 70°C (160°F).
P24FF00 Temperature Too Commonly the coolant lines to the DEF tank
High
are swapped.
DEF quality low and SCR efficiency low.
P207F00 Reductant Quality
Commonly a DEF quality issue.
Diagnostic Steps For Yellow Codes
1. Check the sensor wiring harness connection.
• Disconnect the harness and make sure there is no damage to
the wires or pins, corrosion, or water ingress in either of
the connectors. If damage is found replace in accordance with FSB
258-040.
; Live UI
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2. Verify the DEF quality is at an acceptable value.
• Use refractometer part number 88890105 to verify the DEF
quality. See illustration below.
3. Verify that the DEF tank is not frozen.
4. Ensure that the DEF tank is adequately filled.
5. Clear the Fault Codes.
6. Start the engine. Run the engine on high idle for 2 minutes at 1000
rpm or higher.
7. Turn the Engine Off, Key Off for 15 seconds.
8. Start the engine. Run the engine on high idle for 2 minutes a second
time.
Evaluate the Results
If any of the faults shown in the yellow chart above return active:
Replace the DEF Level Sensor in accordance with Impact instructions
and the wires routed as shown in FSB 258-040.
If none of the faults in the yellow chart above return: No
troubleshooting or replacement of the DEF Level Sensor is necessary.
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Rules for Replacement
• Warranty will only cover replacement of the UQLS if one of the codes in
Yellow section above is present. If the UQLS is suspected to have failed
with no codes present, an eService case is required for further
evaluation.
• Standard Diagnostic Time for a DEF Level Sensor is 0.6 hrs.
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Tags
mack
def quality
volvo
p205b64
p206b64
def level sensor
u02a200
p206c00
p203b00
p24ff00
p203c00
p206a13
p205a13
uqls
p203a13
p207f00
p205c00
p203f00
Related links and attachments
FSB 258-040
Feedback
Give feedback
to help improve the content of this article
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