GROUP

NUMBER

ENGINE

DATE

Technical Service Bulletin

20-EM-002H

MODEL

JULY, 2020

ELANTRA (ADa)

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

SUBJECT:

Description: This bulletin provides a procedure for replacing the thermostat on certain 2019 Elantra
vehicles. The thermostat may not function properly and may result in Diagnostic Trouble Codes
P0128 or P2181. To correct this condition, follow the procedure outlined in this bulletin to replace
the thermostat and air bleed the cooling system after refilling.
No drivability issues are associated with this condition.
DTC

DESCRIPTION

P0128

Coolant Thermostat (Coolant temperature below thermostat regulating temperature)

P2181

Cooling System Performance

APPLICABLE
VEHICLES:

Certain 2019 Elantra (ADa)* with 2.0L Gasoline (Nu) MPI engine

NOTE: *Elantra (ADa) vehicles have VINs starting with “5NP”.
Parts Information:
MODEL

PART NUMBER

DESCRIPTION

Elantra (ADa)

25500-2E085-QQH

Thermostat

PHOTO

NOTE: This Part number may also be used on 17~18MY ADa (VIN: 5NP) when servicing as warranty.
Warranty Information:
OP CODE

OPERATION

OP
TIME

CAUSAL P/N

Elantra (ADa) 00DA21R0

Thermostat
Replacement

0.9

25500-2E085-QQH

MODEL

NATURE CAUSE
CODE
CODE
I3T

ZZ3

NOTE 1: Submit claim on Campaign Claim Entry Screen
NOTE 2: If a part is found in need of replacement while performing the repair for this TSB, and the
affected part is still under warranty, please submit a separate claim using the same Repair Order. If
the affected part is out of warranty, submit a prior approval request for goodwill consideration prior to
performing the work.
Circulate To: Service Manager, Warranty Manager, Service Advisors, Technicians, Fleet Repair

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

SUBJECT:

Service Procedure:
1.

Open the hood and loosen the radiator cap.

!

CAUTION

DO NOT open the cap when the
engine is hot.

2.

Lift the vehicle on a hoist.
Use a 10mm socket and ratchet to remove 7
bolts as shown.
Use a trim tab or similar tool to remove 12
plastic fittings and remove the undercover.

3.

Place a clean container under the radiator.
Use pliers to loosen the plastic drain plug for
the radiator and drain approximately 1/2 gallon
of coolant.
Tighten the plug after draining the coolant.

NOTICE
The drained coolant will be re-used
during the repair.
4.

Lower the vehicle.
Place the same coolant container under the engine.

TSB #: 20-EM-002H

Page 2 of 7

SUBJECT:

5.

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

Locate the lower radiator hose with integral
quick disconnect under the alternator.
For vehicles with a white retainer:
Insert a 90° pick or similar tool under the silver
tab. Gently rotate the pick clockwise and lift the
silver tab up. Pull the white retainer out of the
tab.

6.

Press the tabs on the left and right sides of the
quick disconnect and pull the radiator hose
from the thermostat.

7.

Press the tab on the bottom side of the coolant
temperature sensor connector and disconnect
the connector.

TSB #: 20-EM-002H

Page 3 of 7

SUBJECT:

8.

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

Use a 12mm socket and ratchet to remove the
nuts for the thermostat and remove the
thermostat.
Install the new thermostat and tighten the nuts
to the specified torque.
Tightening torque:
23 Nm (17 lb-ft)

9.

Reconnect the coolant temperature sensor
connector.

10. Reinstall the radiator hose to the thermostat.


Push firmly until a click is heard from the
quick disconnect.



Insert the white retainer into the tab (if
applicable).

TSB #: 20-EM-002H

Page 4 of 7

SUBJECT:

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

11. Refill the cooling system and prepare for air
bleeding.
 Attach a large fill funnel to the filler neck.
 Pour the previously drained coolant in Step
3 into the fill funnel, making sure that the
coolant is clean and free of debris.
 Keep the funnel filled to 1/3 level during the
air bleeding process.

12. Elevate the FRONT LH corner of the vehicle.
 Park vehicle on level ground with parking
brake ON, and block the rear wheels.
 Raise the front left side of the vehicle at the
lift point approximately 100mm (4 inches)
higher than the rest of the vehicle.

Raise FRONT LH corner approx. 100mm (4”)

13. Gently squeeze the 2 upper radiator hoses
leading to the filler neck Y-Junction several
times to initially release any trapped air.
 Hose (A) leading towards the engine
 Hose (B) leading towards the radiator

NOTICE
(Fill funnel not shown in this picture
only for visual purposes.) Keep the
funnel attached to the filler neck and
partially filled with coolant until all
air bleeding steps are complete.

A

B

14. With the GDS connected to monitor the engine coolant temperature (ECT), start the engine and
allow the engine coolant temperature to warm up to 75°C (167°F) at idle.
 To assist the initial engine warm up, turn off the heater blower.
 While the engine is idling and coolant temperature is still cold, squeeze the radiator
hoses (A & B) several more times before engine warms up.

TSB #: 20-EM-002H

Page 5 of 7

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

SUBJECT:

15. When the minimum engine coolant
temperature of 75°C (167°F) has been
reached, use the GDS to perform the coolant
air bleeding.
 From the GDS home page, Select AUTO
VIN > Software Management > Engine
Control > Engine coolant filling mode.
 Follow the prompts on the GDS to begin
the air bleeding process of opening the
electric thermostat, and then perform the
Engine REV steps below.

NOTICE
After warm up has been achieved, monitor for signs of coolant temperature overheating.
 Shut the engine off if coolant boils over or is about to overflow the fill funnel.
 Check coolant fan function and then resume after the engine has cooled sufficiently.
16. Set HVAC to the following to stabilize the coolant temperature during Engine REV steps:
 Temperature to maximum HOT
 A/C indicated ON
 Blower at approximately ¾ speed
17. Perform the following Engine REV steps to help purge the remaining trapped air:
a) REV and hold the engine speed to approximately 1,100 RPM for 1 minute.
b) REV and hold the engine speed to approximately 1,400 RPM for 10 seconds.
c) IDLE for 1 minute. (Check the level of the fill funnel and replenish coolant if necessary.)
d) Repeat Steps (17a) through (17c) for at least 5 cycles, while observing for purged air.
e) Shut the engine off.
f) Allow the engine to cool with the funnel still attached and filled (observe for purged air).

NOTICE
If purging of air is still observed, repeat all of Step 17 at least 2-3 times, or as necessary.
18. After the engine and coolant has fully cooled to lukewarm temperature, remove the fill
funnel and reinstall the radiator cap.
 Check the coolant reservoir level. Fill to FULL if necessary.
TSB #: 20-EM-002H

Page 6 of 7

SUBJECT:

ENGINE THERMOSTAT REPLACEMENT DTC P0128 / P2181

19. Clean any coolant residue under the engine.
Check for leaks from the thermostat.
Reinstall the undercover.
Tightening torque:
5 Nm (44 lb-in)

20. Check for Diagnostic Trouble Codes and erase any DTC.
Erase the DTC in the BlueLink system according to TSB 12-BE-005-2.
Drive the vehicle to confirm proper engine coolant temperature operation.

TSB #: 20-EM-002H

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