LI20.10-P-072886

M17x with CEL for P012800 in the ME Control Unit: "The
Coolant Temperature is Below the Specified Temperature"
Topic number
LI20.10-P-072886
Version
1
Function group
20.10 - Coolant pump, coolant thermostat
Date
4/20/21
Validity
All M17x Engines
Reason for change
Complaint
CEL on with Code P012800 "The Coolant Temperature is Below the Specified Temperature"
Cause
Under investigation
Remedy
1.
2.
3.
4.
5.
6.
7.
During all the tests below ensure that HVAC system is completely off
Complete the guided test of the thermostat from hot and cold
This is done by answering yes and no to the initial question at the beginning of the test
Perform the test again with R48 unplugged
Bleed the cooling system as outlined in AR20.00-P-1142-04A (NOTE: Pease use all the tools specified in the
document)
Evacuate the system for 20-30 minutes instead of the 5 minutes specified by step 22 of the document
Once the system is bled, perform the guided test of R48 once more
If the response curve of the thermostat touches or crosses the upper or lower bound on any of the tests, replace the
thermostat and follow the bleeding procedures outlined above.
If the thermostat was replaced and the system was bled OR if all the tests pass, perform the following "WARM
START" and "COLD START" tests outlined below twice each:
WARM START
•
•
Begin with the engine coolant temperature at approximately 50 degrees C
Activate the AC system, if defrost is not in use open the windows
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© Copyright Mercedes-Benz AG
HENRAND
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•
•
•
•
Drive the car normally until a coolant temperature of 75 degrees C is achieved
Depress the accelerator pedal 50% for ~5 seconds (partial acceleration)
Let off the accelerator pedal and let the car coast for ~10 seconds
Continue to drive the car normally
COLD START
•
•
•
•
•
Drive for ~7 miles (normal driving)
Shut off the engine in a parking lot (or similar), wait 30 seconds, then restart and continue driving
Depress the accelerator pedal 50% for ~5 seconds (partial acceleration)
Let off the accelerator pedal and let the car coast for ~10 seconds
Continue to drive the car normally
If the code does not reappear, release the vehicle. If the code does reappear, open a PTSS case and include:
•
•
•
Initial quick test with fault freeze
ME control unit log
All test results from steps 1 through 5
Attachments
File
Description
AR20.00-P-1142-04A.pdf
R48 test answer no FAIL.pdf
R48 Test, Answer "NO": FAILED TEST
R48 test answr yes unplugged FAIL.pdf
R48 Test, Answer "YES": FAILED TEST
R48 test plugged in cold FAIL.pdf
R48 Test, Plugged In Cold: FAILED TEST
R48 test unplugged hot FAIL.pdf.pdf
R48 Test, Unplugged Hot: FAILED TEST
WIS-References
Document number
Title
Note
AR20.00-P-1142-04A
Pour in coolant and bleed coolant sys- none
tem
Symptoms
Power generation > Engine management > Indicator lamp > Engine diagnosis > lit
Parts
Part number
ES1 ES2 Designation
A1772005500
Quantity Note
THERMOSTAT
EPC
1
X
Operation numbers/damage codes
Op. no.
Operation text
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© Copyright Mercedes-Benz AG
Time
HENRAND
Damage
code
Note
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