Renewing engine control unit J623 (master control unit): Audi Q7 (BHT, BMC, BSB, BTE, …)

🧭 Before you start

Fits: Audi Q7 (4L, 2005–2015)

• Renewed: shear bolts

Don't miss

• If the adaption values of the injectors cannot be read out of the old (defective) engine control unit, they must be entered into the new engine control unit manually and the adaption procedure must be performed accordingly.
• Disregard (item 2).
• The two shear bolts screwed into the engine control unit do not need to be heated. They should be removed without being heated.
• After installation, the locking plate must be re-fitted on the engine control unit J623.
• The injector delivery calibration and injector voltage calibration influence the engine power and exhaust emissions.

🔧 Engine codes this applies to

📋 Procedure

1. Before removing the engine control unit J623, the adaption values of the injectors and the ash deposit mass must be read out. Use . [Note: If the adaption values of the injectors cannot be read out of the old (defective) engine control unit, they must be entered into the new engine control unit manually and the adaption procedure must be performed accordingly.]
2. Switch off ignition and remove ignition key after storing electronic file containing adaption values.
3. Pull off rubber seal on plenum chamber (front).
4. Unclip plenum chamber cover (right-side) and lift it slightly.
5. Reach under plenum chamber cover and unclip engine control unit (1) from bracket. [Note: Disregard (item 2).]

6. ⚠ Heating the thread of the locking plate also heats up the shear bolts and parts of the metal housing. Take care to avoid burns. It is also important to ensure that only the thread is heated and none of the surrounding components if at all possible. These should be covered if necessary. — Unscrew shear bolts using mole grips (see arrow in illustration).
7. The two shear bolts screwed into the engine control unit do not need to be heated. They should be removed without being heated.
8. Detach protective housing from connectors.
9. Unscrew two bolts securing retainers for engine control unit J623.
10. Release connectors on engine control unit J623 and unplug connectors.
11. Take out old engine control unit J623 and connect new engine control unit J623.
12. After installation, the locking plate must be re-fitted on the engine control unit J623.
13. Clean threaded holes for shear bolts to remove any residue from locking fluid. This can be done using a thread tap.
14. Always use new shear bolts.
15. Carefully clip cowl panel trim into retainer at windscreen.
16. After renewing the engine control unit, the "“Injector delivery calibration values”" with the "“Injector voltage calibration”" values must be adapted additionally in the engine control unit J623. [Note: The injector delivery calibration and injector voltage calibration influence the engine power and exhaust emissions.]
17. If only the engine control unit J623 (master) is renewed, the following injectors must be re-adapted: cylinders 1, 4, 6 and 7. Also see notes on .
18. On vehicles with particulate filter the current mileage (km) reading must be stored in the engine control unit J623 via an adaption procedure.

Other AUDI procedures

• Removing and installing coolant pipe (top right) – Audi A8 D3
• Checking fuel pressure regulator and residual pressure (engine code letters BHT)
• Removing and installing suction-jet pump (left-side) – Audi
• Removing and installing suction-jet pump (right-side) – Audi
• Checking exhaust flaps – Audi A8 D3 6.0
• Removing and installing toothed belt – Audi · 56 torque figures
• Removing engine – Audi A8 D3 · 41 torque figures
• Removing camshaft timing chain from camshafts – Audi A6/A7 C7 · 38 torque figures
• Installing engine – Audi A8 D4 · 36 torque figures
• Removing and installing camshaft timing chain · 29 torque figures