Electrical equipment

Fault location tree

~2min read
ALP 1 No communication with the airbag control unit

INSTRUCTIONS

Special feature: To diagnose the vehicle's control units, put the ignition in diagnostic mode (+ after forced ignition), as follows:

  • Vehicle card on the card holder, long press (more than 5 seconds) on the "start" button when starting conditions are not met.
Make sure the diagnostic tool is not the cause of the fault by trying to communicate with a control unit on another vehicle. If the tool is not the cause and communication cannot be established with any other control unit on the same vehicle, check the battery voltage and carry out the necessary work to obtain a compliant voltage (10.5 V < battery voltage < 16 V).
Check the presence and condition of the airbag control unit power supply fuse.

Check the ECU connector connection and the condition of its terminals.

Check that the ECU is correctly supplied:

  • Disconnect the airbag control unit and fit the 22-way adapter (Elé. 1685)
  • Check and confirm the presence of ignition-on (+ after ignition) between the terminals marked earth and + after ignition.

Check that the diagnostic socket is correctly supplied:
  • + before ignition on pin 16
  • + after ignition on pin 1
  • Earth on pins 4 and 5.

Using the 22-way adapter (Elé. 1685), check the continuity and insulation of the lines of the airbag control unit / diagnostic socket link between:

Terminal block CAN H line → Pin 6 of the diagnostic socket
Terminal block CAN L line → Pin 14 of the diagnostic socket

If communication still cannot be established after these checks, contact your Techline (see the "Help" chapter for this procedure).

AFTER REPAIR

Once communication is established, rectify any faults that have been reported.

Test yourself

A quick Renault Megane quiz: every answer comes with an explanation and a link to the manual page.