Engine Controls - Multiple Air Flow Sensor Codes Set
Date: February 9, 2009Order No.: S-B-07.07/83
Supersedes:
Group: 07
SUBJECT:
Model 164.122/822
Model 211.022
Model 251.122
Hot Film Mass Air Flow Sensor
If you receive customer reports in the above model vehicles of Diagnostic Trouble Codes (DTC) faults (listed above) related to the hot film mass air flow sensor (HFM) and/or intake air temperature sensor which are stored in the fault memory of the CDI4 / CDI5 engine control unit. This may be caused by air leakage in the following areas:
1. The intake air line upstream of the air filter (Figure 1, 1) and the clean air line between the air filter and the turbocharger (Figure 1, 2). Check the intake air lines for leaks. Visually inspect all connections for leaks, cracks, incorrect assembly and correct as needed.
2. The charge air system (green seal ring between turbocharger and charge air line to noise damper, seal rings at the connections between the charge air hoses and the Henn couplings) (Figure 1, 3). Check charge air system for leaks. Visually inspect all of the connections for oil leakage, cracks, incorrect assembly, and pinched or damaged o-rings on the charge air hoses.
3. For oil leakage at the air intake duct at the intake of the turbo charger, refer to DTB S-B-09.20/29.
Note:
Oil coating present in the clean air duct (Y-pipe, Figure 1, 2) with integrated hot film mass air flow sensors does NOT cause signal drift and therefore does NOT generate fault entries.
If vehicle mileage exceeds 18,500 miles, a prematurely clogged air filter can result in fault entries in vehicles operated in dirty/dusty conditions. In cases of vehicles operated in dirty/dusty conditions with heavily contaminated air filters, replace the air filter elements. After replacing the air filters (Figure 1, 5), reset the learned values for the air filter contamination (SDS menu: CDI4/5 control unit --> Control unit adaptation --> Reset air filter learned values).
Note:
Ensure that the air filters are installed in the correct side and that the covers are completely seated (Figure 1, 1A and 1B).
Note:
If the checks listed above revealed faults in the system and these have been rectified, always reset the HFM drift compensation (SDS menu CDI4/5 control unit --> Control unit adaptation --> Reset values for HFM drift compensation).
To resolve contact faults at electrical connections for the hot film mass air flow sensors and the engine control unit CDI4 / CDI5, check connectors for proper seating/engagement, inspect pins on plugs and sockets (pin may be bent back or damaged or corrosion of pins due to moisture) by disconnecting and reconnecting connector.
Note:
Copy of the SDS short test and all tests performed must accompany returned parts. If the documentation is missing or does not support the diagnosis, the warranty claim may be debited.
Parts Information
Note:
The following allowable labor operations should be used when submitting a warranty claim for this repair. This information has been generated on February 9, 2009. Please refer to Netstar -> Star TekInfo --> Star Time for the most current labor time allowance.
In Case of Warranty, use the table.