Engine Controls - Multiple DTC Troubleshooting: Overview
Date: November 2009Order 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, 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.
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, 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).
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).
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.
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).
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.
Check for cracks (Figure 9) and open (broken) connection (Figure 10 & 11) on all hoses connected to the intake manifold.
In case of Warranty, use the table above.