Slave Engine Control Module, Replacing
Slave Engine Control Module, Replacing
Engine management is controlled by two engine control modules.
Both engine control modules communicate via private CAN-Bus.
Engine Control Module (ECM) 2 (J623) (Master) shares with Engine Control Module (ECM) 2 (-J624-) (Slave) which functions need to be performed.
The two engine control modules look identical. If both engine control modules are removed, they must be marked before removal to prevent them from being interchanged when re-installing.
Master ECM 1: e.g. with "M"
Slave ECM 2: e.g. with "S"
Engine Control Module (ECM) 2 (J624), removing
- Connect vehicle diagnostic, testing and information system (VAS 5051) and select vehicle system "11 - Engine electronics 2". Ignition must be switched on.
On the screen of the vehicle diagnostic, testing and information system (VAS 5051), the control module identification and coding are displayed.
- Allow control module identification to be displayed and then print it out.
- Remove right cover from plenum chamber.
Position 1 shows the Master ECM (J623).
Position 2 shows the Slave ECM 2 (J624).
To increase the difficulty with which the ECM connectors can be accessed, the ECM - 1 - is secured in a metal housing - 5 - with retaining tabs - 2 - and shear bolts - 3 - and - 4 -.
Special tools, testers and auxiliary items required
• Heat gun - 1 - (from wiring harness repair kit (VAS 1978))
• Nozzle attachment - 2 - (also from wiring harness repair kit (VAS 1978))
• Small, commercially available locking pliers (vise grips)- 3 -
CAUTION!
By heating the threads, the retaining tabs, shear bolts and parts of the metal housing become very hot. Do not burn yourself on these parts! Make sure that only the threads are heated as much as possible, and not any of the surrounding parts. Possibly cover these parts.
The threads of the shear bolts - 4 - (not screwed into the ECM) are coated with a locking compound. For this reason, the threads must be heated with the heat gun to remove both bolts.
The threads of both shear bolts - 3 -, that are screwed into the ECM, are not coated with a locking compound. The threads in the ECM housing must not be heated (unintentional heating of the ECM).
- Set adjustment on heat gun as shown in illustration, with temperature potentiometer - 2 - set to maximum heat and two-stage air flow switch - 3 - set to level 3.
- Heat threads of connector-side shear bolts as shown in illustration for approx. 25 to 30 seconds.
CAUTION!
By heating the threads, the retaining tabs, shear bolts and parts of the metal housing become very hot. Do not burn yourself on these parts! Make sure that only the threads are heated as much as possible, and not any of the surrounding parts. If necessary, cover these parts.
- Remove shear bolts with locking pliers (see direction of arrow).
• Both shear bolts that are screwed into the ECM do not require heating to be removed. They can be removed without heat.
- Disconnect metal retainers from the ECM connectors.
- Remove both bolts from retainers for ECM 2 (-J624-) (Slave) and pull ECM forward.
- Release and disconnect connector from ECM 2 (-J624-).
- Remove old ECM 2 (-J624-) and install new ECM.
Engine Control Module (ECM) 2 (-J624-), installing
• Perform the installation in reverse order of removal. Thereafter, the engine control module must be equipped with the metal retainer. Always use new shear bolts.
• The procedures to follow after connecting the new ECM are to be found in Guided Fault-finding.
Procedures after connecting new ECM
- Follow instructions in Guided Fault-finding.
- Enter correct vehicle into Guided Fault-finding
- Press "Go to" button
- Select "Function/component selection"
- Select "powertrain"
- Select "engine code"
- "01 - On Board Diagnostic (OBD) capable systems
- "Motronic fuel injection and ignition system"
- Select "Functions"
- Select "Engine Control Module (ECM)"