Command interpretation

STEP 1

Measure the resistance of the exhaust gas recirculation valve between its pins 1 and 5: - If its resistance is not 8 Ω ± 0.5 at 20 ˚C, replace the EGR valve. Check the continuity and the absence of parasitic resistance on the connections between:

Injection ECU, brown connector B, 48-pin, pin L2 → Pin 5 of the exhaust gas recirculation valve connector
+12 V after relay → Pin 1 of the exhaust gas recirculation valve connector

If no valve movement is perceptible when running command AC002, check the operation of the ECU output stage:

• either with an oscilloscope (set to 5 V/division and 2 ms/division time base)

With the EGR valve connected, connect the oscilloscope ground to the battery ground and the positive probe to pin 5 of the EGR valve. Clear any EGR valve fault, then run command AC002: the oscilloscope must display a square wave with an amplitude of 12.5 V at a frequency of 140 Hz (with an opening duty cycle varying from 20 to 70%).

• or with a voltmeter:

With the EGR valve connected, connect the voltmeter ground lead to pin 2 of the EGR valve and the positive lead to pin 1. Clear any EGR valve fault, then run command AC002; the voltmeter must display two successive voltages approximately equal to the product of the battery voltage and the current opening duty cycle.

Successively: 2.5 V for an opening duty cycle of 20%, then 8.75 V for an opening duty cycle of 70% (ten cycles).

• If the measurement is correct, go to step 2.
• If the oscilloscope (or voltmeter) shows no control signal, or a DC voltage, contact your technical hotline before replacing the engine control unit.

STEP 2

Check for leaks in the exhaust gas recirculation circuit.

Carry out the necessary repairs.

Checking the operation of the exhaust gas recirculation valve: Disconnect the connector and remove the valve. If removal reveals that its valve is stuck in the open position, replace the exhaust gas recirculation valve.

Otherwise, with the valve removed, reconnect the connector.

Clear the fault and run command AC002. Check:

• the valve movement (valve travel from 0 to 2.5 mm for an opening duty cycle of 20% and 6 to 7 mm for an opening duty cycle of 70%),
• that there is no play between the valve and its control rod, as well as the general condition (carbon build-up, sticking, etc.),
• that the valve closes when the command is complete.

If no movement of the EGR valve is detected during test AC002, or if these checks show that the valve is irreparably jammed or seized, replace the EGR valve. (After replacement, follow procedure RZ005 described in the "Help" section.)

Preliminary information

1 Checking the high-pressure air circuit for leaks:

Ducts disconnected or punctured, pressure sensor disconnected or incorrectly fitted (check for the seal), intercooler punctured.

To check the intercooler: with the vehicle stationary, hold the engine speed between 3500 and 4000 rpm and check for leaks.

Replace the solenoid valve if its resistance is not 15.4 Ω ± 0.7 at 20 ˚C.

Injection ECU, connector C, grey 32-pin, terminal E1 → Terminal 1 of boost solenoid valve

Repair if necessary.

Check for +12 V after relay on terminal 2 of the boost solenoid valve (coming from terminal G1 of connector PPM1 of the protection and communication unit).

Engine off, check that the control rod is in the rest position.

Start the engine and check that the control rod moves to the upper stop.

(With the engine off, the control rod must return to the rest position.) If the control rod movements are not correct, carry out the following checks:

1) Checking the control vacuum:

• Disconnect the inlet hose from the solenoid valve and connect it to a pressure gauge,
• Start the engine and let it stabilise at idle,
• If the vacuum does not reach 800 mbar ± 100, check the vacuum circuit from the vacuum pump.
• Stop the engine, reconnect the inlet hose and go to step 2.

2) Checking the solenoid valve control:

• disconnect the outlet hose from the solenoid valve,
• start the engine and let it stabilise at idle,
• hold the solenoid valve and block the outlet fitting with your thumb,
• if no vibration of the solenoid valve can be felt, check the operation of the ECU output stage (step 5).

3) Checking the solenoid valve operation:

• connect the pressure gauge to the outlet fitting of the solenoid valve,
• start the engine and let it stabilise at idle,

If the vacuum does not reach 800 mbar ± 100, replace the solenoid valve.

4) Checking the turbocharger operation:

a) Connect a vacuum pump to the hose connected to the turbocharger control actuator,

• Apply a vacuum of 800 ± 100 mbar:

If there is a leak, replace the turbocharger (the actuator cannot be separated from the turbocharger).

b) Check the movement and adjustment of the control rod (see Repair Manual, chapter 12B).

If the control rod is seized, replace the turbocharger.

c) Engine cold, engine off:

• Remove the turbocharger air intake duct and check that the compressor turns freely on its shaft.

d) If the problem persists:

• check for leaks at the exhaust manifold,
• check that the exhaust is not blocked.

Carry out the necessary repairs.

5) Checking the ECU output stage: (solenoid valve connected)

Only carry out this operation if the checks in step 2 are inconclusive.

Or with a voltmeter:

• Connect the voltmeter earth lead to terminal 2 of the solenoid valve and the positive lead to terminal 1.
• Clear any fault on the solenoid valve, then run command AC004:

The voltmeter must display ten cycles of two successive voltages, approximately equal to the battery voltage multiplied by the current duty cycle.

i.e. approximately 2.5 V (for a duty cycle of 20%) then approximately 8.7 V (for a duty cycle of 70%).

Either with an oscilloscope (set to 5 V/division and 2 ms/division time base):

• connect the oscilloscope earth lead to the battery earth, and the positive probe to terminal 2 of the solenoid valve,
• clear any fault on the solenoid valve, then run command AC004:

The oscilloscope must display a square wave of 12.5 V amplitude at a frequency of 140 Hz (with the duty cycle changing successively from 20 to 70%).

• If the measurement is correct, replace the solenoid valve.
• If the measurement shows no control signal or a DC voltage, contact your technical hotline before replacing the engine control unit.

STEP 1

Check the resistance of the pressure regulator between terminals 1 and 2:

• If its resistance is not 3 Ω ± 0.5 at 20 ˚C, replace the regulator.

Check continuity and absence of parasitic resistance on the links between:

Injection ECU, brown connector B, 48-pin, terminal M4 → Terminal 2 of the rail pressure regulator connector
+12 V after relay → Terminal 1 of the rail pressure regulator connector

If, when running command AC011, a slight hissing sound and a clicking of the pressure regulator can be heard, go to step 2. Otherwise, check the operation of the ECU output stage:

• (Or with the ammeter):

With the solenoid valve connected, clamp the current probe onto the wire of terminal 1 of the solenoid valve (observe the current direction). Clear any fault on the fuel pressure solenoid valve, then run command AC011. The ammeter must display ten cycles of two successive currents: approximately 0.6 A then approximately 2 A.

• Or with a voltmeter:

Solenoid valve connected: connect the voltmeter ground lead to pin 2 of the fuel pressure solenoid valve and the positive lead to pin 1. Clear any fault stored on the fuel pressure solenoid valve, then run command AC011. The voltmeter must show two successive voltages, each approximately equal to battery voltage multiplied by the current duty cycle.

That is, in succession: ~2.5 V for a duty cycle of 20%, then ~8.75 V for a duty cycle of 70% (ten cycles).

• Or with an oscilloscope (set to 5 V/division and time base 1 ms/division):

Solenoid valve connected: connect the oscilloscope ground to battery ground and the positive probe to pin 2 of the fuel pressure solenoid valve. Clear any fault stored on the fuel pressure solenoid valve, then run command AC011. The oscilloscope must show a square wave with an amplitude of 12.5 V at a frequency of 185 Hz (with the duty cycle changing from 20% to 70%).

• If the reading is correct, replace the regulator.
• If the reading is not correct, contact your techline.

STEP 2

If rail pressure is too high:

Check the injectors' operation: see the "injector diagnosis" help section of this note.

Check the operation of the rail pressure sensor. Diagnosis PR038.

If these checks show no fault, replace the regulator.

If rail pressure is too low:

Check the operation of the rail pressure sensor. Diagnosis PR038.

Check the low-pressure diesel circuit priming.

Check the connections of the diesel filter.

Check the condition of the filter (clogging and water saturation).

Check that there are no air bubbles between the filter and the high-pressure pump.

Check the low-pressure and high-pressure diesel circuits for leaks (visual checks, smell, etc.): pump body, pressure relief valve, hoses, rail and injector fittings, injector wells, etc.

Check that the seal on the pressure regulator is correctly fitted.

Check the injectors' operation: see the help section "injector diagnosis" of this note.

Carry out the necessary repairs.

• Check the resistance of the intake flap solenoid valve between pins 1 and 2.

  Replace the solenoid valve if its resistance is not 46 Ω ±3 at 25 °C.

• Check continuity and absence of parasitic resistance on the links between:

Injection ECU, brown connector B, 48-pin, pin J4 → Pin 1 of the throttle flap solenoid valve connector
+12 V after relay → Pin 2 of the throttle flap solenoid valve connector

• Check that there is ~900 mbar of vacuum at the solenoid valve inlet hose.

  Carry out the necessary repairs (conformity and sealing of the vacuum circuit).

B) Ignition on, engine off:

• Check that the intake flap is open; if not, clean or replace the diffuser housing.
• Disconnect the inlet and outlet hoses from the solenoid valve.
• Connect a vacuum pump to the inlet fitting and apply a vacuum of ~900 mbar. If there is a leak, replace the solenoid valve.
• Run command AC014.
• If the solenoid valve opens (the pump vacuum gauge returns to atmospheric pressure), go to step C.
• Otherwise, with the solenoid valve connected, check the operation of the ECU output stage with a voltmeter:

Voltmeter ground lead → Pin 1 of the solenoid valve
Voltmeter positive lead → Pin 2 of the solenoid valve

Clear any fault stored on the solenoid valve, then run command AC014.

The voltmeter must show ten "ON-OFF" cycles (8.75 V then 2.5 V).

If the measurement is correct, replace the solenoid valve.

If the measurement shows no control signal, contact your techline.

C) Ignition off:

• Connect a vacuum pump to the flap control actuator and apply a vacuum of ~900 mbar:
• If the actuator does not hold the vacuum, replace the diffuser housing (the actuator cannot be separated from it).
• If the actuator holds the vacuum but the flap does not move, clean or replace the diffuser housing.
• If the actuator holds the vacuum and the flap moves, carry out several actuations to check that there is no sticking.

Check the diffuser housing and its flap for contamination, and clean if necessary.