Emissions - MIL ON/Code 2761 Stored in DME memory
SI B 12 44 06Engine Electrical Systems
March 2007
Technical Service
This Service Information bulletin supersedes S.I. B12 44 06 dated February 2007.
[NEW] designates changes to this revision
SUBJECT
E46 SULEV: DME FC 2761, Secondary Air System - Diagnostic Hints
MODEL
E46 with M56 (SULEV)
SITUATION
^ "Service Engine Soon" light is illuminated.
^ Fault code 2761 (Secondary air system) is stored in MS45.1 DME control module.
^ On a previous shop visit, the vehicle was reprogrammed with DIS/GT1 CD V39.1, or higher (SI B12 30 06), which contains the updated DME software for secondary air system activation.
CORRECTION
On a customer complaint basis, and when all listed above conditions are fulfilled, follow the procedure below:
1. Check the detailed fault description in DIS/GT1 tester. There are following possibilities:
^ FC 2761 Secondary-air system "Secondary-air valve or hose blocked" (most likely the vacuum supply part of the system is affected; e.g. non-return valve, vacuum solenoid valve, check valve, vacuum hoses, wiring from DME to vacuum solenoid valve).
^ FC 2761 Secondary-air system "Secondary-air pump not active" (most likely the electrical part of the system is affected; e.g. pump, relay, wiring between DME and relay/ pump/ secondary air mass meter/ fuse).
^ FC 2761 Secondary-air system "Leakage between secondary-air pump and valve, no airflow is detected by oxygen sensor signals" (most likely defective hose from the air pump to non-return valve, or defective non-return valve).
^ FC 2761 Secondary-air system "Secondary-air flow too low" (most likely defective secondary air mass flow sensor, possibly blocked secondary air filter).
2. Check if the coolant temperature is between 1°C and 35°C (32°-85°F). Cool down the engine if needed.
3. Check the battery voltage. Recharge battery if the voltage is less then 11.5 V.
4. [NEW] Check vacuum hoses between the intake manifold and the secondary air non-return valve. Make sure that they are not blocked, broken, porous, or hardened. Replace vacuum hoses if necessary (using the updated parts listed below), and at the same time eliminate the black/white check valve between the intake manifold and solenoid valve, as described in step 6 of the procedure.
5. Remove the outlet hose from the secondary air pump, activate the pump with DIS/GT1 tester, measure the secondary-air mass airflow sensor signal with multimeter at DME break-up box module 4, pin 15. Measure the voltage at the air pump connector:
^ If the air pump is not running, or if it is running but the pump's voltage is less then 10 V, then inspect the air pump for water condensation/biding, check air pump relay, fuse F36/50A, harness and connectors, contacts between DME and the air pump, including the relay. Replace defective components if necessary.
^ If the air pump is running with voltage exceeding 10 V, but the secondary air mass airflow sensor signal is less then 3 V, then check secondary-air filter for clogging. If found not defective, then replace the secondary-air mass airflow sensor.
IMPORTANT:
Do not use any type of lubricant (e.g. grease, oil, silicone spray, etc) to ease the reconnection of the secondary air system hoses. Oil/silicon based lubricants may cause contamination and sticking of the non-return or vacuum solenoid valves.
6. [NEW] If the secondary air pump is running correctly, reconnect the outlet hose to the pump and install a pressure gauge at a vacuum line of the non-return valve. Loosen the air pump to determine a start-up of pump's operation (from the pump's torque) and measure the elapsed time between air pump activation and vacuum build-up readings at the non-return valve:
^ If vacuum is less then 300 mbar, or
^ If time elapsed between pump start-up and vacuum build-up at the non-return valve is more then 1.5 seconds, then replace a vacuum solenoid valve and inspect vacuum hoses between non-return valve and vacuum solenoid valve. Replace defective components if necessary. Use vacuum line (P/N 11 72 7 574 486) between non-return valve and the solenoid valve. Eliminate from the system the black & white plastic check valve. Replace vacuum hose between solenoid valve and intake manifold with 230 mm length of hose P/N 11 65 7 803 732.
^ If vacuum is more then 300 mbar and the elapsed time is less then 1.5 seconds, then replace a secondary non-return valve using the updated part P/N 11 72 7 573 932 with the gasket P/N 11 72 7 514 860. Replace vacuum line between non-return and solenoid valves (P/N 11 72 7 574 486), and eliminate the black & white plastic check valve, as described above.
[NEW] IMPORTANT:
Do not replace a vacuum controlled non-return valve with the push-type non-return valve from the M54 engine system.
[NEW] PARTS INFORMATION
[NEW] WARRANTY INFORMATION
Covered under the terms of the BMW New Vehicle Limited Warranty.
Disclaimer