Engine Controls - MAF/IAT Sensor DTC Troubleshooting
Date: November 2009
Order No.: S-B-07.61/039d
Supersedes: S-B-07.61/039c (May 2006)
Group: 07.61
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Revision History:
Revision Date Purpose
d November Models 204, 207 and 212 Added.
2009
c May 2006 Additional Models application (164.175, 219.375, 251.175)
b June 2005 Applies to all Model 215 and 220 vehicles;
screen shots and notes under Step B/B1 Changed
SUBJECT:
TROUBLE SHOOTING FAULT CODES RELATED TO:
^ ADAPTATION LIMITS OF LAMBDA CONTROL
^ MASS AIR FLOW SENSORS / INTAKE AIR TEMPERATURE SENSOR
MODELS
This bulletin explains how to troubleshoot fault codes P2004-[ ], P2006-[ ], P2017-[ ], P2086-[ ], P2016-[ ], and P2085-[ ] by providing a special
fault tree for each P-code. Troubleshoot each fault code by solving it before moving onto the next code. If you have no codes or a code other than
the above P-codes DO NOT REPLACE THE AIR MASS SENSOR.
Requirements for ALL air mass sensor replaced under warranty:
^ Printout of all fault codes of the ME2-SFI-motor electronics (short test).
^ Freeze frame data of all fault codes stored in the ME2-SFI-motor electronics.
^ Signal voltage printout Fig. 4 (page 10) of component B2/5 (Hot film MAF sensor).
^ Returned MAF sensors without the required information will be debited back to the dealer.
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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 02/04. All mass air flow sensors will be tested and if found to be functioning correctly will be sent back to the dealer and the
corresponding claim will be debited.
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In case of Warranty, use the table above.
MAF Sensor/Self-Adaptation of Mixture Formation
MAF sensor and self-adaptation of mixture formation trouble-shooting diagram
Repair process for fault code P2004-[ ]
Functional description of the MAF sensor:
Upon engine start, a current is passed through the MAF sensor, heating the wire film to a certain 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. This signal is then sent to the ECU 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 air intake temperature sensor is also mounted in the mass air flow sensor.
The monitor of the MAF sensor is active after a specified time after engine start and above a specified engine speed threshold.
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Repair process for fault code P2004-[2]
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Repair process for fault code P2004-[1]
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Repair process for fault code P2004-[4]
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Repair process for fault code P2004-[8]
Description of test steps of remedy process fault codes P2004-[ ]
Step A: Test voltage supply 5V of component B2/5 ( MAF sensor).
Step A1: Additionally please check the voltage supply of component B2/5 (MAF sensor) also with running engine to extend this test on higher
temperature and vibration conditions of the MAF sensor.
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Step A2: If the measured value is not O.K. please follow the next steps shown in Fig. 2:
Step B: Test voltage supply 12V of component B2/5 ( MAF sensor).
Step B1: Additionally please check the voltage supply of component B2/5 (MAF sensor) also with running engine to extend this test on higher
temperature and vibration conditions of the MAF sensor.
If the measured value is not O.K., check for a short circuit on the wiring or connector of the12V battery voltage cable and also the Z-connection
(Z7/35) of the MAF sensor (B2/5).
Step C: Test signal voltage of component B2/5 ( MAF sensor) by means of actual value.
Note:
The specified value of the HFM-SFI voltage depends on the intake air temperature (B2/5b1):
Specified value
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Note:
The signal voltage test is to be done with ignition ON and engine off. If the engine speed (also shown in the screen of the signal voltage test, Fig. 4)
is not 0 rpm, the specified value of the signal voltage can't be used for the signal voltage test.
Note:
In order to avoid the possibility of a false signal voltage reading please only perform the signal voltage test with the air filter housing completely
assembled on the hot film MAF sensor. Also please ensure that there is no exhaust gas extraction device on the tail pipe of the vehicle. Any air flow
thru the hot film MAF sensor during the signal voltage test will cause a false reading.
If the status of the relevant actual value is out of range from the specified value and all test requirements were fulfilled, replace the mass air flow
sensor and send this part with the required DAS original printouts to our Quality Evaluation Center.
Note:
Before replacing the 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 ME2-SFI-motor electronics (short test).
^ Freeze frame data of all fault codes stored in the ME2-SFI-motor electronics.
^ Signal voltage printout Fig. 4 (page 10) of component B2/5 (Hot film MAF sensor).
Returned MAF sensors without the required information will be debited back to the dealer.
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 02/04.
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Repair process for fault code P2006-[1]
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Repair process for fault code P2006-[2]
Description of test steps of remedy process fault codes P2006-[ ]
Step D1: Check component B2/5b1 (Intake air temperature sensor) using actual value.
Step D2: Check plausibility of actual value B2/5b1 (Intake air temperature sensor) in control module N3/10 (ME-SFI control module).
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Step D3: Test voltage supply of component B2/5b1 (Intake air temperature sensor).
Step D4: Test internal resistance of component B2/5b1 (Intake air temperature sensor).
If the measured value of the resistor of the intake air temperature sensor is out of range from the specified value and all test requirements were
fulfilled, replace the mass air flow sensor and send this part with the required DAS-printouts (see below) to our Quality Evaluation Center.
Note:
Before replacing the 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 ME2-SFI-motor electronics (short test).
^ Freeze frame data of all fault codes stored in the ME2-SFI-motor electronics.
Document the value of the measured resistance and the approximate temperature of the area surrounding component B2/5b1 for test purposes in our
Quality Evaluation Center in the dealer text section of the warranty claim.
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Returned MAF sensors without the required information will be debited back to the dealer as of repair date March 12, 2004.
Note:
Only original, readable printouts with the VIN number (DAS-readout) of the vehicle are accepted.
Description of the Adaptive Mixture Control as Part of Lambda Control
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 Fig. x). 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.
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 (injection time) + 0.9 ms means additional fuel needs to be added at idle speed range. Look for cause why engine is running lean.
A partial load adaptation factor of 0.885 (88.5% of regular injection time) means fuel is taken away in partial load range. Look for cause why engine
is running to rich.
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Repair process for fault code from adaptation of mixture formation
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Self adaptation of mixture formation (right/left bank) of cylinders is at minimum limit value at idle speed (P2017-[2], P2086-[2]).
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Self adaptation of mixture formation (right/left bank) of cylinder is at maximum limit value at part load (P2016-[1], P2085-[1]).
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Self adaptation of mixture formation (right/left bank) of cylinder is at minimum limit value at part load (P2016-[2], P2085-[2].
Description of test steps of failure analysis in case of a adaptation of mixture formation fault code
Step E: Check for air leaks in the air intake system.
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Check for proper installation of the mass air flow sensor to intake manifold. Refer to Fig. 11 and Fig. 12 as examples of improper installation.
In case of improper installation, correct the installation of the mass air flow sensor to the intake manifold (Fig. 13 and 14) and if necessary, replace
the clamp (A 112 141 03 40). Do not replace the mass air flow sensor!
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Step F1: Test fuel pressure and internal leaks of fuel system.
Step F2: Test delivery of component M3 (fuel pump).
Note:
Take also a fuel sample and check for water or other contaminations.
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Step G1: Inspect component Y62yx (Cylinder x injector) for leaks.
Step G2: Inspect operation and spray pattern of component Y62yx (Cylinder x injector).
Step H: Follow the below steps to re-adapt the adaptation values for lambda control.
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Step H1: Adaptive pre-control for lambda control (at part load).
Step H2: Adaptive pre-control for lambda control (at idle speed).
Note:
The path to the screens to perform the adaptive pre-control for lambda control (Fig. 19 and Fig. 20) in DAS are as follow:
^ ME-SFI 2.8 Motor electronics 2.8
^ Fault path tests performed
^ Measures for initiating the fault path tests
^ Step 6 Self adaptation of mixture formation
