TECH TIP
TT-19-001 DEF PUMP DIAGNOSTIC TECH TIPDTC P20E8
SUPERSEDES TT-16-003
GROUP: 0-GENERAL
TECH TIP NO: TT-19-001
DATE: 1-9-2019
REFERENCE: HMM-190104-J1

SUBJECT VEHICLES: 11MY-20MY Conventional Trucks

equipped with a J08 engine or 12MY-20MY Cab-Over Engine
(COE) equipped with a J05E engine.
Note: This Technical Tip is provided as technical
information and is not authorization for a warrantable repair.
DESCRIPTION OF CONDITION:

Subject vehicles may exhibit a MIL lamp on due to DTC
(Diagnostic Trouble Code) P20E8 setting in the DCU (Dosing
Control Unit). This DTC sets when low pressure of the DEF
(Diesel Exhaust Fluid) pump is detected. Please review the
diagnostic tips below regarding the DEF pump.

PARTS:
Part Number

Part Description

Quantity

S17M0E0010

Inlet Connector

As Required

DIAGNOSTIC TIPS
DTC P20E8- DEF System Pressure Low
This DTC sets when low DEF pressure is detected by the DCU. Low DEF
pressure may be caused by a restriction on the DEF sensor pickup tube, a
restriction in the tank vent tube, a restriction in the DEF pump lines, or a
restriction in the DEF pump inlet connector. Restrictions in the system may
occur due to contamination entering the DEF tank during a refill. Low DEF
pressure may also be caused by an external leak in one of the DEF lines or
DEF injector. These items need to be inspected and/or addressed prior to
replacement of the DEF pump.
Supplemental Information:
• Make certain the DEF tank vent tube is clear of crystallization or clogs. A
restricted vent tube will result in low DEF pressure and DTC P20E8.
• Replacement of the DEF pump inlet connector (Part No. S17M0E0010) is
REQUIRED during step 7 of the diagnostic procedure. If DEF pump
pressure is normal after replacement of the inlet connector, no further
repairs are needed. Warranty claims for DTC P20E8 will not be reimbursed
if the DEF pump inlet connector is not first replaced prior to replacement of
the pump assembly. An inlet connector must be charged out on the
warranty claim. DO NOT replace the white backflow connector for DTC
P20E8.
• If contamination is found inside of the DEF tank on step 6 of the
diagnostic procedure, follow the recommended procedures in the
Workshop Manual. Replacement of SCR system components due to fluid
contamination IS NOT a warrantable failure.
• For 11MY-14MY Conventional trucks and 12MY-16MY COE trucks,
ensure that the inlet filter screen is present on the DEF tank as outlined by
SB-15-031 on Hinonet.
• The pump contains a filter which has a 150,000 mile maintenance interval
and should ONLY be replaced for maintenance purposes. Replacement of
this filter has not proven effective for resolving DTC P20E8. The filter may
ONLY be replaced under warranty for external leaks.
• When the DEF pump is to be replaced for DTC P20E8, it is
recommended to drain the DEF tank from the drain plug, rinse the tank
out with water, and refill the DEF tank with fresh DEF. This
may prevent recurrence of DEF pump failure due to potential
particulate contamination inside the DEF tank that cannot be
seen with the naked eye.

Leaks Around Filter Cap
If the DEF pump filter cap is improperly torqued, a leak around the filter
cap, as depicted on the right, may occur. DO NOT replace the DEF pump
for this condition. This is not a leak from the pump housing. If a leak occurs
within the DEF pump, DEF will first come out of the electrical connector.
The crystallized DEF can be scraped off and/or dissolved with water.
Replace the DEF filter (Part No. S17K0E0011, which includes a new seal)
to address this condition.

DTC P204F in Engine ECU With No DTC in DCU
If DTC P204F is present in the engine ECU, the DEF pump may fail to
operate when performing the pump Leak Test or the Injector dosing test. To
clear DTC P204F, perform the UREA SCR System Memory Reset. From
the Engine ECU Data Monitor and Active Test menu, select Active Test
Setting> UREA SCR Related Memory Reset> then follow the prompts to
complete the reset. After performing the SCR reset, clear DTC P204F from
the engine ECU, and cycle the ignition off for 60 seconds. Turn the ignition
on, and then read out DTC’s in the Engine ECU and DCU. If no DTC’s are
present, the DEF Pump tests can now be performed.