Fault location tree

• That fuse F5 (after ignition) is correct.
• That the power supplies to the injection relay holder are correct.
• That the impact sensor is correct: continuity between its pins 1 and 3 at rest (before impact); +12 V battery → pin 3 (via fuse); continuity between its pin 3 and pin 1 of the injection relay.
• That the injection relay is correct: 65 Ω ±5 Ω between its pins 1 and 2; infinite resistance between its pins 3 and 5 (contact open); resistance < 0.2 Ω between its pins 3 and 5 (contact closed).

Disconnect the engine control unit (ECU) and check that there are no conductive elements on the ECU pins. If removal reveals any contamination, clean or repair it and try to establish communication.

If the fault persists, connect the terminal block ref: Elé. 1681 to the engine harness. Check continuity and the absence of parasitic resistance on the following connections:

ECU connector A pin B4 → Diagnostic socket pin 7 (K-line)

Check the power supplies for conformity:

ECU connector B pin E3 → + After ignition,
ECU connector A pin D3 → Ground,

By bypassing the normally open contact of the injection unit power relay, i.e. pins 3 and 5 of the relay holder:

ECU connector B pins M3 and M2 → + 12 V battery (via test jumper)

Check the continuity of the connection between:

ECU connector B pin D4 → pin 2 of the injection unit power relay holder.

• If communication is established with another control unit in the same vehicle, go to step 2.
• If communication cannot be established with any other control unit in the same vehicle, a faulty control unit may be disturbing the K-line and/or L-line. To locate it, use the elimination method by disconnecting in turn all control units connected to these lines (according to the wiring diagram and equipment fitted).

Air conditioning, airbag, anti-lock brakes - dynamic stability control, body control module (BCM), instrument panel, communication unit, parking assistance.

Try to establish communication after each disconnection. If communication is established after a disconnection, carry out the diagnosis of the control unit concerned.

• If the fault persists, reconnect the control units listed above and disconnect the ECU. Try to establish communication with another control unit.

  If communication is established, go to step 2.

• If communication still cannot be established, disconnect the K-line and make sure it is isolated from + 12 V and from ground at pin 7 (K-line) and pin 15 of the diagnostic socket (if wired). Carry out the necessary repairs.

STEP 2

Replace the engine control unit. If necessary, modify the configuration of the new unit to match the options fitted to the vehicle.

WARNING

If the "IMA" function is in service, follow the ECU replacement procedure defined in the "Help: IMA Calibration" section of this note.

Check priming of the low-pressure fuel circuit.

Check the power supply to the fuel heater.

Check the operation of the glow plug (preheating) system.

Check that the fuel and engine temperatures are consistent.

If the effect persists, check the rail pressure and carry out diagnosis AC004: "Boost pressure solenoid valve" and AC011: "Rail pressure regulator".

Check the conformity of the air flow information (use diagnostic PR050).

Check that the position of the exhaust gas recirculation (EGR) valve is correct (use diagnostic AC002): "EGR solenoid valve".

If the effect persists, carry out the injector diagnosis (see the "Help" section).

If the injection noise occurs at all engine speeds: carry out an injector diagnosis (see the "Help" section).

Check the condition of the terminals on the injector and pressure regulator connectors.

Check that the fuel is correct.

Check the conformity of the air flow information (use diagnostic PR018: "Estimated air flow" and PR131: "EGR air flow deviation").

If the effect persists, check the rail pressure and carry out diagnosis AC004 "Boost pressure solenoid valve" and AC011: "Rail pressure regulator".

During a road test, when changing gear, monitor parameter PR202 (CP3) or PR097 (CP1). If it varies without noticeable influence on the rail pressure, carry out diagnosis AC011: "Rail pressure regulator".

If the effect persists, carry out the injector diagnosis (see the "Help" section of this note).