Ignition Control Module

Replace the ignition control module on the M275 6.0L V12 BiTurbo engine to restore proper ignition system operation.

Warnings

Tools required

Parts

• Ignition control module × 1 — A2751530079 or equivalent OEM
• Engine cover seal (if damaged) × 1 — Use OEM specification

Preparation

1. Ensure engine is completely cool to the touch
2. Park vehicle on level surface and engage parking brake
3. Disconnect battery negative terminal and wait 15 minutes
4. Remove engine cover by lifting upward from front clips and pulling forward to release rear mounts
5. Document or photograph all electrical connections before disconnection
6. Have Star Diagnostic System available for post-installation coding

Procedure

1. 1

   Access ignition control module area
   On the M275 V12, the ignition control module is located on the left side (driver side) of the engine valley, beneath the intake plenum area. Remove the left bank plastic cover trim pieces using Torx T25 screws. There are typically 4-6 screws securing the trim.
   Torque spec

   Cover Screws15 Nm (11 lb-ft)
2. 2

   Disconnect ignition coil connectors
   The ignition control module connects to all 12 ignition coils. Working from front to back on the left bank, press the release tabs and disconnect the electrical connectors from cylinders 1, 3, 5, 7, 9, and 11. Label each connector position if not already marked.
   ⚠Do not pull on wires; always grasp the connector body to prevent terminal damage.
3. 3

   Disconnect right bank ignition coil connectors
   Access the right bank (passenger side) and disconnect the electrical connectors from cylinders 2, 4, 6, 8, 10, and 12. These connectors route to the central ignition control module.
   ℹ️On some model years, you may need to remove additional trim panels on the right side for better access.
4. 4

   Disconnect main ignition control module harness
   Locate the main wiring harness connector at the ignition control module body. This is a multi-pin connector with a sliding lock mechanism. Slide the red or gray lock tab outward, then press the release tab and pull connector straight back from module.
   ⚠The connector lock must be fully released before attempting to remove connector to avoid breaking the locking mechanism.
5. 5

   Remove module mounting bracket
   The ignition control module is secured to a mounting bracket on the engine. Remove the bracket bolts (typically 2-3 bolts) using a 13mm socket. Support the module and bracket assembly as you remove the final bolt.
   Torque spec

   Bracket Bolts27 Nm (20 lb-ft)
6. 6

   Separate module from mounting bracket
   The ignition control module is secured to its mounting bracket with mounting bolts. Remove these bolts using a 10mm socket to separate the module from the bracket. Note the orientation of the module for correct reinstallation.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)
7. 7

   Inspect and clean mounting surfaces
   Examine the mounting bracket and engine mounting point for corrosion, damage, or debris. Clean all mounting surfaces with electrical contact cleaner. Check all connectors for corrosion or bent pins and clean as necessary.
   ℹ️Any corrosion on electrical contacts should be cleaned with electrical contact cleaner and allowed to dry completely.
8. 8

   Install new ignition control module to bracket
   Position the new ignition control module onto the mounting bracket in the same orientation as the original. Install mounting bolts and torque to specification using a torque wrench.
   Torque spec

   Mounting Bolts37 Nm (27 lb-ft)
9. 9

   Install module and bracket assembly to engine
   Position the ignition control module and bracket assembly onto the engine mounting location. Install bracket bolts and torque to specification. Ensure the module is properly seated and aligned before final torque.
   Torque spec

   Bracket Bolts27 Nm (20 lb-ft)
10. 10

    Reconnect main module harness
    Connect the main wiring harness connector to the ignition control module. Push connector firmly until it clicks into place, then slide the lock tab into the locked position. Apply light pull pressure to verify secure connection.
    ℹ️Optional: Apply a small amount of dielectric grease to connector sealing surfaces to prevent moisture intrusion.
11. 11

    Reconnect all ignition coil connectors
    Working systematically, reconnect all 12 ignition coil connectors to their respective positions on both banks. Ensure each connector clicks securely into place. Verify each connection by attempting to pull the connector free with light force.
    ⚠Incorrect coil connector placement will cause misfires and potential engine damage. Verify each position matches documentation taken during disassembly.
12. 12

    Reinstall trim covers
    Reinstall all plastic trim covers and engine cover components. Install cover screws and torque to specification using a torque wrench. Ensure all clips and fasteners are properly seated.
    Torque spec

    Cover Screws15 Nm (11 lb-ft)
13. 13

    Code module with Star Diagnostic System
    Reconnect the battery negative terminal. Connect Mercedes-Benz Star Diagnostic System to the vehicle. Navigate to engine control unit programming and perform ignition control module coding/adaptation procedure. Follow all on-screen prompts to complete SCN coding for the new module.
    ⚠️The vehicle will not start until the ignition control module has been properly coded to the engine control unit using Star Diagnostic System.
    ⚠Do not attempt to start the engine before completing the coding procedure or fault codes will be stored and additional diagnosis time will be required.

Reassembly

1. Reinstall engine cover by aligning rear mounts first, then pressing down on front clips until they engage
2. Clear any diagnostic trouble codes stored during the replacement procedure
3. Perform ignition system adaptation using Star Diagnostic System

Verification

• Verify Star Diagnostic System shows successful module coding with no communication errors
• Start engine and verify smooth idle with no misfires on all 12 cylinders
• Use Star Diagnostic System to monitor real-time ignition timing data for all cylinders
• Perform test drive and verify normal engine performance under various load conditions
• Scan for any stored diagnostic trouble codes and address if present
• Verify all ignition coils are firing correctly by checking coil on-time values in Star Diagnostic System

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