Mercedes Benz C 300 4MATIC # S-07_61-59A Date: 091113
Engine Controls - Multiple DTC Troubleshooting
Date: November 2009
Order No: S-B-07.61/59A
Supercedes: S-B-07.61/59, February 2006
Group: 07
Revision: Models 204, 207, 212 Added.
SUBJECT:
Troubleshooting DTC Fault Codes Related to:
^ Adaptation Limits of Lambda Control
^ Mass Air Flow Sensor/Intake Air Temperature Sensor
Models
204, 207, 212, 171.454, 171.456, 203.052, 203.054, 203.092, 203.056, 203.087, 209.356, 209.456, 211.056, 211.087, 211.256, 211.287, 164.186,
251.165, 221.171
This bulletin explains how to troubleshoot DTC fault codes 0337, 0338, 0341, 0342, 0537, (0620), 0745, 0746, 0749, 0750, 0789, 0790, 0793,
0794, 1045, 1046, 1047, 1048, 1049, 1050, 1051, 1052, 1345, 1346, 1347, 1349, 1350, 1351, 1352, 1857, 1858, 2025, 2026, 2029, 2030, 2032,
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2089, 2090, 2091, 2092, 2093, 2094, 2095, 2096, 2181, 2082 by providing special diagnostic trees based on DAS for each fault code.
Troubleshoot each fault code by solving it before moving onto the next code.
Required DAS-printouts for warranty returns:
^ Printout of all fault codes of the ME 9.7-motor electronics 9.7 (Quick test).
^ Freeze frame data of all fault codes stored in the ME 9.7-motor electronics 9.7.
^ All other required printouts within this document.
^ Returned hot film mass air flow sensor (component B2/5) without the required information will be debited back to the dealer as of repair date
February 20, 2006.
Note:
Only original, readable printouts with the VIN number (DAS-readout) of the vehicle will be accepted. The required printouts can be made only with
DAS-Version starting 11/2005. A hot mass air flow sensor (component B2/5) may be returned and debited back to the dealer should it be determined
that it was not properly tested with DAS and in fact, is working correctly.
General Information: Description of the adaptive mixture control as part of the lambda control:
The catalytic after treatment of the exhaust gas using a closed loop three way catalytic converter has proven to be a highly effective means of
meeting the current low emission limits.
Approximately 14.7 kg of air are required for complete combustion of 1 kg of gasoline. The excess air factor lambda is used to define this A/F ratio.
The engine must be operated within a very narrow range in which lambda = 1 +/- 0.005 . Such precision can only be achieved with precise closed
loop control of the A/F mixture with a lambda oxygen sensor installed upstream of the converter. A second lambda sensor downstream of the
catalytic converter increases the precision even further.
To compensate individual engine differences and long-lasting drifts in sensors and actuators of the injection system and also to compensate small not
measured air leakage, the lambda control contains an adaptive pilot control. This adaptive pilot control takes over the controller correction in two
different ranges (see Figure 2). It takes a certain time of learning in each range, until the correction is completed.
Deviations of the A/F ratio in range 1 is compensated by an additive factor and in range 2 by a multiplying factor. There are individual factors for the
right and the left banks of the engine.
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Note:
In the idle speed range, the additive factor can also be affected by the multiplicative factor. For example, if the multiplicative factor (adapted in
range 2) at idle speed is too large, the additive factor (adapted in range 1) will adapt in a negative direction.
Example:
Idle adaptation of 3 % means mixture control at idle is adding fuel. Look for cause of engine is running lean. Partial load adaptation of 0.80 means
mixture control at partial load is taking fuel away. Look for cause of engine is running to rich.
Repair process for fault codes from adaptation of mixture formation:
Self-adaptation of mixture formation (right/left bank) for enrichment at partial load is above the permissible limit (fault codes 0337, 0341,
0789, 0793, 1045, 1049, 2089, 2093).
If this value is greater than 1.20 there may be unmetered air (a leak) in the intake system or not enough fuel is being supplied to the combustion
chamber.
The oxygen sensor measures a lean signal which causes the lambda control to compensate for the problem by making the mixture richer.
Note:
Self-adaptation of mixture formation is at the limit or out of the range on one cylinder bank only, indicates that the hot film mass air flow sensor is
not the cause. Do NOT replace the hot film mass air flow sensor (component B2/5)!
Self-adaptation of mixture formation (right/left bank) for enleanment at partial load is below the permissible limit (fault codes 0338, 0342,
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0790, 0794, 1046, 1050, 2090, 2094).
If this value is less than 0.80 the fuel pressure may be higher than 4 bar (affects both cylinder banks) or a fuel injector is leaking. In this case too
much fuel is supplied into the combustion chamber. The oxygen sensor measures a rich signal, which causes the lambda control to compensate for
the problem by making the mixture more lean.
Note:
Self-adaptation of mixture formation is at the limit or out of the range on one cylinder bank only, indicates that the hot film mass air flow sensor is
not the cause. Do NOT replace the hot film mass air flow sensor (component B2/5)!
Self-adaptation of mixture formation (right/left bank) for enrichment at idle speed is above the permissible limit (fault codes 0745, 0749,
1045, 1049, 2091, 2095).
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If the actual value of self-adaptation in the idle speed range is 3 % above the stated set values on both cylinder banks, there may be unmetered air (a
leak) in the intake system or the connected vacuum and crank chase ventilation lines. In this case not enough fuel is being supplied into the
combustion chamber. The oxygen sensor measures a lean signal which causes the lambda control to compensate for the problem by making the
mixture richer.
Note:
Self-adaptation of mixture formation is at the limit or out of the range on one cylinder bank only, indicates that the hot film mass air flow sensor is
not the cause. Do NOT replace the hot film mass air flow sensor (component B2/5)!
Self-adaptation of mixture formation (right/left bank) for enleanment at idle speed is below the permissible limit (fault codes 0746, 0750,
1046, 1050, 2092, 2096).
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If the actual value of self-adaptation at the idle speed range is 3 % below the stated set values the fuel pressure may be higher than 4 bar (affects both
cylinder banks) or a fuel injector is leaking. In this cases too much fuel is supplied into the combustion chamber. The oxygen sensor measures a rich
signal, which causes the lambda control to compensate for the problem by making the mixture more lean.
Note:
Self-adaptation of mixture formation is at the limit or out of the range on one cylinder bank only, indicates that the hot film mass air flow sensor is
not the cause. Do NOT replace the hot film mass air flow sensor (component B2/5)!
In the case of an adaptation mixture formation fault code on both cylinder banks please check the following:
^ Check seal of component B2/5 (hot film mass air flow sensor).
^ Inspect air filter housing for correct installation.
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A damaged seal (Figure 3) between the hot film mass air flow sensor and the air filter housing or a improper installation of the air filter housing
(Figure 4) can cause a false air flow measurement. The measured value of this improper air flow does not represent the actual air mass. The
difference between the measured value (based on the false measurement) and the actual value of the air mass in the engine is corrected by the lambda
control. In this case a rich or lean condition on both cylinder banks can occur.
Note:
Please be informed that models 203 and 209 do not have air intake housing mounting clip due to design packaging.
^ Check for restriction on air filter inlet (diesel restrictor plate).
A further source for a false air flow measurement can be a restriction before the air filter (plastic bag, ∧) or in the air filter inlet (Figure 5).
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Figure 6 shows a restrictor plate for a diesel engine. If this restrictor plate is installed in a vehicle with gasoline engine (M272, M273) it causes also
a false air flow measurement!
^ Inspect hot film mass air flow sensor for correct installation.
Incorrect installation (Figure 7) of the hot film mass air flow sensor (component B2/5) to the intake manifold might be source for two problems:
- A false air flow measurement (improper air flow at sensor element).
- Unmetered air (leak) at the intake system (lean running condition on both cylinder banks).
In case of improper installation, correct the installation of the hot film mass air flow sensor to the intake manifold (securely place the clips).
Do NOT replace the hot film mass air flow sensor!
^ In case of "Self adaptation of mixture formation for enrichment is above the permissible limit" check for air leaks in the air intake system and
connected hoses.
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Check for cracks (Figure 9) and open (broken) connection (Figure 10 & 11) on all hoses connected to the intake manifold.
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In case of Warranty, use the table above.
Hot Film Air Flow Sensor Related Fault Codes
Functional description of the hot film air flow sensor (component B2/5):
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Upon engine start, a current is passed through the hot film air flow sensor, heating the sensor element (Figure 12) to a certain constant temperature.
As air passes through the sensor, this film is cooled and the sensor determines how much electricity is required to keep the film up to temperature.
This enables the sensor to determine how much air (in weight) is passing through the sensor at any given moment. It also recognizes the direction in
which the air is flowing it is able to take pulsation and backflows into account. This means that the hot film air flow sensor is able to measure the
actual air mass independent of pulsation and backflows. This signal is then sent to the ME9.7 engine control unit which it compares to a
preprogrammed map to deliver fuel and ignition spark, taking into account other engine inputs such as engine rpm and temperature. The hot film air
flow sensor HFM 6 transmits a frequency (HFM 5 of engine management system ME2.8 transmitted a signal voltage) to the ME9.7 engine control
unit. The integrated deflection particulate contamination and reduce drift over lifetime.
The air intake temperature sensor is also mounted into the mass air flow sensor
Repair process for hot film air flow sensor (component B2/5) related fault codes:
Repair process for fault codes 1345, 1346, 1347:
The fault codes are stored in case of a problem with the cables or the connectors of the hot film mass air flow sensor (component B2/2) or the hot
film mass air flow sensor itself. Please use the symptom overview for components B2/5 (hot film mass air flow sensor) to locate the problem.
NOTE
Fault code 1347 is stored when the connector (5-pin) of the hot film mass air flow sensor (component B2/5) was unplugged during two key cycles.
To check the signals of component B2/5 (Hot film MAF sensor) on vehicles with ME 9.7 - Motor electronics 9.7 there are two guided test available
in DAS:
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1.) Check signal of component B2/5 (Hot film MAF sensor) via actual value with engine OFF.
2.) check signal of component B2/5 (Hot film MAF sensor) via actual value with engine speed greater then 3500 rpm.
Repair process for fault codes 1349, 1350, 1351, 1352:
These fault codes are stored if the measured air mass is implausible compared to the position of the throttle valve actuator. in this case, please check
component m16/6 (throttle valve actuator) for proper operation.
Repair process for fault codes 1857, 1858:
These fault codes are stored if the ratio of the hot film mass air flow sensor signal to intake manifold pressure is out of range. In this case, please
check component B28 (pressure sensor) for proper operation.
Repair process for fault codes 2181, 2182:
Check for a proper connection of the connector (5-pin) on the hot film mass air flow sensor (component B2/5).
NOTE
Fault code 2182 is stored when the connector (5-pin) of the hot film mass air flow sensor (component B2/5) was unplugged during two key cycles.
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Diagnostic Tree for Hot film air Flow Sensor
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Symptom Overview for Hot Film Mass Air Flow Sensor
Note:
The HFM-SFI signal check of component B2/5 (Hot film mass air flow sensor) via actual value with engine OFF is to be done with ignition ON and
engine OFF. If the engine speed (also shown in the screen of the HFM-SFI signal test) is not 0 rpm, the specified value of the HFM-SFI signal can't
be used for this test.
If the status of the relevant actual value is out of range from the specified value and all test requirements were fulfilled, replace the hot film mass air
flow sensor (component B2/5) and send this part with the required DAS original printouts (see below) to our Quality Evaluation Center.
Note:
Before replacing the hot film air flow sensor, check for sand and dirt particles in the clean side (between air filter and engine) of the air intake system
and clean if necessary. Check complete air intake system with air cleaner and repair as necessary.
Required DAS-printouts for warranty returns:
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^ Printout of all fault codes of the ME 9.7 - Motor electronics 9.7 (Quick test).
^ Freeze frame data of all fault codes stored in the ME 9.7 - Motor electronics 9.7.
^ Printouts (Figure 14, 15) of the HFM-SFI signal of component B2/5 (Hot film mass air flow sensor).
Returned hot film mass air flow sensors (component B2/5) without the required information will be debited back to the dealer as of repair date
February 20, 2006.
Note:
Only original, readable printouts with the VIN number (DAS-readout) of the vehicle are accepted. The required printouts can be made only with
DAS-Version starting 11/2005.
Air Temperature Sensor Related Fault Codes
Functional description of the air temperature sensor (component B2/5b1):
The air temperature sensor (component B2/5b1) is integrated into the hot film mass air flow sensor (component B2/5). It contains a temperature
dependent resistor whose resistance falls with rising temperature. The engine management system (ME9.7 Motor electronics 9.7) uses the change in
the applied voltage in order to determine the air temperature.
Repair process for air temperature sensor (component B2/5b1) related fault codes:
Repair process for fault code 2025, 2026:
These fault codes are stored in case of a problem with the cables or the connectors of the intake air temperature sensor (B2/5b1).
Note:
Fault code 2026 is stored when the connector (5-pin) of the hot film mass air flow sensor (component B2/5) was unplugged during two key cycles.
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Diagnostic Tree for Fault Code 2025
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Diagnostic Tree for Fault Code 2026
Repair process for fault code 2029, 2030, 2032
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These fault codes are stored if the measured value of the intake air temperature sensor (component B2/5b1) is implausible.
During the plausibility of intake air temperature procedure the actual value of intake air temperature (component B2/5b1) and coolant temperature
(component B11/4) is compared at engine cold start. A fault code will be stored when these two temperature values are not close enough to each
other. Please check component B11/4 (coolant temperature sensor) for proper operation.
Note:
Fault Code 1101, 1102, 1103, 1104, 1599, 1600, 2069, 2070 are related to the Ambient temperature display temperature sensor (component B14).
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Diagnostic Tree for Coolant Temperature Sensor
If the measured value of the resistor of the intake air temperature sensor (component B2/5b1) is out of range from the specified value and all test
requirements were fulfilled, replace the hot film mass air flow sensor (component B2/5) and send the part with the required DAS-printouts (refer ti
Repair process for fault codes of adaptation of mixture formation) to our Quality Evaluation Center.
Note:
Before replacing the hot film mass air flow sensor, check for sand and dirt particles in the clean side (between air filter and engine) of the air intake
system and clean if necessary. Check complete air intake system with air cleaner and repair as necessary.
Required DAS-printouts for warranty returns:
^ Printout of all fault codes of the ME 9.7 - Motor electronics 9.7 (Quick test).
^ Freeze frame data of all fault codes stored in the ME 9.7 - Motor electronics 9.7.
Note:
Document the value of the measured resistance and the approximate temperature of the area surrounding of component B2/5b1 for test purposes in
our Quality Evaluation Center in the dealer text section of the warranty claim.
Returned hot film mass air flow sensor (component B2/5) without the required information will be debited back to the dealer as of repair date
February 20, 2006.
Note:
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Only original, readable printouts with the VIN number (DAS-readout) of the vehicle are accepted.
Fault Codes of Adaptation of Mixture Formation/Diagnostic Trees
Repair process for fault codes of adaptation of mixture formation - Diagnostic trees of related systems and components:
The main diagnostic tree for adaptation of mixture formation links to several related systems and components. For a complete diagnostic solution it
may be necessary to follow the diagnostic path of a linked diagnostic tree.
Diagnostic Tree for Lambda Control
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Diagnostic Tree for Fuel system (lean condition) - "Fuel Restriction"
211
Diagnostic Tree for Fuel System (rich condition) - "too much fuel"
212
Diagnostic Tree for Fuel injectors
213
Performing Self-Adaptation of Mixture Formation
