Wear of valve seat or valve guide. Engines M260 or M264
Topic number

LI01.30-P-072328

Version

9

Function group

01.30 - Cylinder head

Date

2/2/26

Validity

Passenger car with M260 or M264

Reason for change

Additional notes added and op-codes corrected

Complaint
-Check engine light illuminated.
-Engine runs rough.
-Poor shifting or jerking when accelerating.
-Fault codes stored related to mixture formation, injector quantity adjustment, or misfire.
Note: One or more of the above symptoms can occur. It is possible that no fault codes are stored.

Cause
Leaking valve seat in cylinder head.

Remedy
-Perform cylinder leakage check as noted in WIS group 01.00. If excessive leakage is found determine if leak is from
intake or exhaust valves.
-If leakage is found from intake or exhaust valves, remove cylinder head and inspect valve seats.
-The complete cylinder head must be replaced if valve seat damage is found. The valve seats can not be reworked.
-Engine oil and filter should be changed after the repair.
Workshop notes cylinder head repair:

1.
2.
3.
4.
5.
6.

The intake rocker arm roller is narrower than the exhaust and they must not be interchanged. Mark the rocker
arms so they are reinstalled in their original location.
Inspect all parts that are being reused (i.e. camshafts, rocker arms) for signs of wear or damage. See WIS doc
AH05.20-P-1000-09SZ for examples of normal and abnormal wear. Replace parts with new if damage or wear is
found.
Check that all rocker arms are correctly located on the camshaft before installing cylinder head cover. Rotate engine at least 2 times and check that there are no problems with rocker arms.
The timing chain tensioner can be reused if it extends fully, has no noticeable problems in prior operation, and
no chain drive components were replaced.
Care must be taken when removing fuel injectors to prevent damage. See WIS doc AR07.03-P-0004-03MM.
Cleanliness must be observed during repair to prevent subsequent complaint or engine damage:

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•
•
•

When cleaning engine block surface, ensure oil ports are sealed to prevent debris from entering oil circuit. Refer
to SI01.40-P-0010A.
No abrasive materials, sharp-edged tools, or unapproved cleaners should be used on engine block surface. Refer to AR01.00-P-0050-01A.
Any debris from cleaning that has entered the cooling jacket should be removed before assembly of engine. The
debris can otherwise cause blockage in the cooling circuit leading to engine overheating.

If any of the parts listed below are found damaged or in need of replacement during cylinder head valve‑seat diagnosis or repair, and the vehicle has warranty coverage, they must be claimed on a separate parts‑only line. These items
are not covered under the cylinder head warranty extension and cannot be included with the claim.

•
•
•
•
•
•
•
•
•
•

Camshafts
Camshaft adjustment solenoids
Camshaft positioners
Fuel injectors
Hydraulic valve play compensating elements
Roller rocker arms
Spark plugs
Timing chain
Timing chain guide rails
Timing chain tensioner

WIS-References
Document number

Title

Note

AH05.20-P-1000-09SZ

General information on checking
camshafts and bearing points of
camshafts

AR01.00-P-0050-01A

Remove sealant

SI01.40-P-0010A

Service Information: Cleaning of
crankcase

AR07.03-P-0004-03MM

Remove injection nozzles

Disclaimer
NOTE: The information contained in this document is intended for use by trained, professional technicians with the
knowledge to properly and safely perform diagnosis and repairs on Mercedes-Benz vehicles, using Mercedes-Benz
approved tools and equipment. It informs service technicians about conditions that could occur in certain vehicles and
provides information that could assist in proper vehicle diagnosis, service, or repair. It does not indicate that a defect
is present in any vehicle referenced in this document nor does it imply warranty coverage. DO NOT assume that a
symptom or condition, or a described cause of a symptom or condition, affects any particular vehicle or groups of vehicles, or that a described repair applies to any particular vehicle or groups of vehicles. There can be multiple causes
resulting in the same or similar symptoms or conditions described in this document, and trained professional service
technicians must use their diagnostic skills to make evaluations on a case-by-case basis. The information contained
in this document does not guarantee warranty coverage nor does it extend the vehicle’s warranty in any way.

Symptoms
Power generation > Engine management > Engine running > Surges
Power generation > Engine management > Engine running > Runs rough/shakes
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Power transmission > Automatic transmission > Function > Engaging process
Power generation > Engine management > Indicator lamp > Engine diagnosis > lit
Power transmission > Automatic transmission > Function > Shifting is rough
Power generation > Engine management > Engine performance > No/poor output
Power transmission > Automatic transmission > Function > Poor shift quality

Parts
Part number

ES1 ES2 Designation

Quantity Note

EPC

A2600106801

M260 Cylinder head kit, with
1
valves, head gasket and intake
manifold seals

For engine M260

X

A2640106407

M264 Cylinder head kit, with
1
valves, head gasket and intake
manifold seals

For engine M264

X

Control unit/fault code
Control unit

Fault text

N3/10 - Motor electronics 'MED41' for combustion engine P030485 - Combustion misfiring of cylinder 4 has been
'M260/M264' (ME) (MED41)
detected. There is a signal above the permissible limit value.
P030385 - Combustion misfiring of cylinder 3 has been
detected. There is a signal above the permissible limit value.
P030285 - Combustion misfiring of cylinder 2 has been
detected. There is a signal above the permissible limit value.
P030185 - Combustion misfiring of cylinder 1 has been
detected. There is a signal above the permissible limit value.
P030085 - Combustion misfiring has been detected. There is a signal above the permissible limit value.
P1CEF85 - Injector injection quantity adjustment for cylinder balancing has almost reached the upper limit value at
at least one cylinder. There is a signal above the permissible limit value.
P219F78 - Mixture formation (cylinder 4) is irregular. The
adaptation or adjustment is incorrect.
P219E78 - Mixture formation (cylinder 3) is irregular. The
adaptation or adjustment is incorrect.
P219D78 - Mixture formation (cylinder 2) is irregular. The
adaptation or adjustment is incorrect.
P219C78 - Mixture formation (cylinder 1) is irregular. The
adaptation or adjustment is incorrect.
P219F77 - Mixture formation (cylinder 4) is irregular. The
commanded position cannot be reached.
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P219E77 - Mixture formation (cylinder 3) is irregular. The
commanded position cannot be reached.
P219D77 - Mixture formation (cylinder 2) is irregular. The
commanded position cannot be reached.
P219C77 - Mixture formation (cylinder 1) is irregular. The
commanded position cannot be reached.
P1CE678 - Injector injection quantity adjustment for uniform mixture formation has detected an excessively rich
mixture at at least one cylinder. The adaptation or adjustment is incorrect.
P1CE577 - Injector injection quantity adjustment for uniform mixture formation has detected an excessively lean
mixture at at least one cylinder. The commanded position
cannot be reached.

Operation numbers/damage codes
Op. no.

Operation text

Damage
code

Note

Damage code- Valve seat exhaust
"worn"

01205D1

Select damage code for valve seat
with most wear

Damage code- Valve seat intake "worn"

01224D1

Select damage code for valve seat
with most wear

006555

Perform oil change

011300

Check cylinder for leaks (spark plugs removed)

015760

Remove/install cylinder head

015801

Check cylinder head (Cylinder head removed)

017105

Replace Cylinder Head (cylinder head
removed, new cylinder head preassembled)

151010

Spark Plugs Remove and Install

201145

Drain/fill correct coolant

401580

Remove/install complete wheel

475140

Relieve fuel pressure

541011

Perform Quick Test

547989

Disconnect ground line of battery for
12V

611075

Remove/Install Engine Compartment
Paneling

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Time

Max claimable time 0.3 hrs

Max claimable time 0.3 hrs

H

CCUSHWA

Only for engine M260

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