P0400

DTC PO4OO
EXHAUST GAS RECIRCULATION FLOW MALFUNCTION (EGR)





Description
- The Exhaust Gas Recirculation (EGR) System aims at reduction of NOx by lowering the combustion temperature through recirculation of a part of exhaust gas into cylinders via the intake manifold.
- This system consists of the EGR Valve, the EGR solenoid valve and Back Pressure Transducer (BPT). The EGR Valve is operated by the vacuum pressure from throttle body via BPT and controls the exhaust gas flow from the exhaust manifold to the intake manifold by open/close operation of the EGR Valve.
- The EGR solenoid valve is controlled by the Engine Control Module (ECM) according to the engine driving condition and opens/closes the vacuum line from the BPT to the EGR valve diaphragm.
- The BPT controls the vacuum pressure to control the amount of EGR according to the engine load.





- The EGR Valve is situated between the exhaust manifold and intake manifold. After opening EGR solenoid valve; EGR valve is opened for receiving throttle port pressure on diaphragm. Then part of the exhaust gas is recirculated into intake manifold.

DTC Detecting Condition
Two consecutive trips with fault.

Trouble Symptom
Poor driving performance on low Engine speed.











1. Check Transmission Type.
- Refer to flow chart.

2. Check DTC PO1O5, PO1O6, P0403, P11O2 on display.
[CHECK]: Check that Subaru Select Monitor or OBD-II General Scan Tool shows P0105, P0106, PO4O3 and P1102.
[YES]: Inspect the relevant DTC.
- Manually check that EGR valve diaphragm is not stuck.
- In this case inspection of P0400 is not necessary after the above items.

WARNING: Be careful when checking EGR valve, since it may be extremely hot.

- After checking the above item, go to Confirmation of actual driving pattern.
[NO]: Go to step 3.

3. Check Vacuum Hose.
[CHECK]: Check vacuum hoses for disconnection, leakage and clogging.
[YES]: Check and repair the following items.
- Two lines of pipes and hoses running between throttle body and BPT.
- Pipe and hose line connecting BPT and EGR solenoid valve.
- Hose between EGR solenoid valve and EGR valve.
- BPT pressure transmitting hose.
[NO]: Go to step 4.

4. Check operation of EGR system.
a. Turn Ignition switch to "OFF".
b. Connect the test mode connector.
c. Turn Ignition switch to "ON".
[CHECK]: Does EGR solenoid valve produce operating sound?
[NO]: Replace EGR solenoid valve.
[YES]: Go to next step.

d. Turn ignition switch to "OFF".
e. Disconnect connector from EGR Solenoid Valve.
f. Connect 12 Volt battery's ground (negative) terminal to one terminal of the EGR Solenoid Valve. Then connect 12 Volt battery's positive terminal to the other terminal of it.

CAUTION: Do not use the 12 Volt Battery installed in the vehicle, because the electrical system may be damaged.

g. Start the Engine.
[CHECK]: Open throttle valve by 5 to 10 degrees and visually check EGR Valve operation.
[YES]: Possibly EGR valve malfunction may be due to freezing or clogging by foreign matter. At this point in time do not replace EGR valve, since it is not faulty. And after the checking, go to Confirmation of actual driving pattern.

NOTE: If malfunction is detected again in the confirmation of actual driving pattern, EGR Valve is faulty. Go to next [CHECK].
[NO]: Go to next [CHECK].

[CHECK]: Is there clogging in the gas outlets of intake manifold or cylinder head? Check by breathing into the outlets.
[YES]: Repair or replace intake manifold or cylinder head. And go to Confirmation of actual driving pattern.
[NO]: Replace EGR Valve. And go to Confirmation of actual driving pattern.

Confirmation of actual driving pattern.
1. Conduct Clear Memory and Inspection Modes.
2. Connect Subaru Select Monitor to the data link connector.
3. Start and warm-up the engine until the radiator fan makes one complete rotation. (All accessory switches are "OFF".)
4. Turn Subaru Select Monitor switch to "ON".
5. Designate mode using tunction key.
Function mode: FA4
6. Drive at 88 ± 5 km/h (55 ± 3 MPH) until the LED No. 5 is turned "ON".

NOTE: Keep the throttle valve opening at the same degree since diagnosis will be interrupted when the opening varies. Diagnosis starts in 190 seconds after starting Engine and takes 4 seconds. Put the gear to "D" range for the diagnosis.

7. Designate mode using function key.
Function mode: FR0
8. Confirm the "No Trouble" indication on Subaru Select Monitor.