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DTC P0400: Exhaust Gas RECIRCULATION (EGR) Flow Malfunction

  1. Raise and support vehicle. Place transmission in Neutral. Start engine and release parking brake lever. Check that rear wheels turn. If rear wheels don't turn, block one rear wheel and rotate other rear wheel forward by hand.
    CAUTION: If EGR valve is hot, it is necessary to wear gloves to avoid burning fingers.
    NOTE: Increasing engine speed to higher than 3000 RPM, driving vehicle or insufficient engine warm-up, will result in interrupting scan tool control.
  2. Check EGR system. If using scan tool, go to next step. If not using scan tool, go to step  4 .
  3. Turn ignition switch off. Connect SUZUKI scan tool to DLC. Start engine. When engine is cool, coolant temperature below 131°F (55°C), race engine and check that EGR valve diaphragm is not operating in this state by touching diaphragm with finger. Warm up engine to normal operating temperature, coolant temperature is above 176°F (80°C). Using scan tool, turn EGR solenoid vacuum valve on. Check to be sure that diaphragm moves. If EGR valve fails to operate properly, go to step  5 . If the diaphragm moves, keep the engine running at idle speed and open EGR valve by hand, and engine should either stop or reduce it's speed. If engine does not stop or reduce speed, EGR passage is clogged. Clean it.
  4. Input vehicle speed to PCM to cause EGR valve to operate. If EGR valve operates properly, go to step  11 . If EGR valve fails to operate properly, go to next step.
  5. Inspect vacuum passage. Start engine and run it at idle speed. With finger placed against vacuum nozzle, check that vacuum is applied. If vacuum is applied, go to next step. If it is not applied, clean vacuum passage by blowing compressed air.
  6. Inspect EGR valve assembly. Disconnect vacuum hose from EGR system check solenoid vacuum valve. Connect vacuum pump gauge to it's hose. Check that EGR valve diaphragm moves smoothly and that it is held at the same position when 20 cmHg of vacuum is applied to EGR valve. If operation is as specified, go to next step. If diaphragm fails to move smoothly, or it isn't held at the same position, replace EGR valve. After checking, be sure to connect vacuum hose.
  7. Inspect EGR pressure transducer. Check filter for contamination and damage. Using compressed air, clean filter. Remove EGR pressure transducer and plug nozzle with finger. Blow air into another nozzle and check that air passes through to air filter side freely. Connect vacuum pump gauge to one vacuum port and plug remaining vacuum port with finger. Blow into pressure port. Apply vacuum to pressure transducer. Vacuum should hold. Stop blowing into pressure port. Vacuum should release. If operation is as specified, go to next step. If operation is not as specified, replace EGR pressure transducer. After checking, install pressure transducer and connect hoses securely.
  8. Disconnect EGR solenoid vacuum valve vacuum hoses from pipes. Turn ignition switch on. Blow into port "A". See Fig 1 . Air should come out of port "B" and not out of filter. If operation is not as specified, go to next step. Start engine and run it at idle speed. Blow into port "A". Air should come out of filter and not out of port "B". If operation is as specified, connect vacuum hoses securely. If operation is not as specified, go to next step.
    Fig 1: Identifying EGR Solenoid Vacuum Valve Ports
    G96I09877Courtesy of SUZUKI OF AMERICA CORP.
  9. With ignition switch off, disconnect harness connector from EGR solenoid vacuum valve. Check resistance between solenoid vacuum valve terminals. Resistance should be 28-36 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EGR solenoid vacuum valve and retest system.
  10. Disconnect vacuum hoses from pipes. Blow into port "A". See Fig 1 . Air should come out of port "B" and not out of filter. Using fused jumper wires, connect 12-volt source to solenoid terminals. Blow into port "A". Air should flow from filter and not from port "B". If operation is as specified, check EGR solenoid vacuum valve harness for an open or short. Repair as necessary and go to next step. If operation is not as specified, replace EGR solenoid vacuum valve and retest system. Connect solenoid valve harness connector and vacuum hoses securely.
  11. Disconnect EGR system check solenoid vacuum hoses from pipes. Turn ignition on. Blow into port "A". See Fig 2 . Air should flow from port "B" and not from port "C". If operation is as specified and using scan tool, go to next step. If operation is as specified and not using scan tool, go to step  13 . If operation is not as specified, go to step  14 .
    Fig 2: Identifying EGR System Check Solenoid Ports
    G96C09879Courtesy of SUZUKI OF AMERICA CORP.
  12. Connect SUZUKI scan tool to DLC and connect vacuum hoses. Warm up and stop engine. Disconnect vacuum hoses from pipes. Turn ignition switch on. Using scan tool, turn EGR system check solenoid vacuum valve on. Blow into port "A". See Fig 2 . Air should come out of pipe "C" and not out of pipe "B". If operation is as specified, go to step  17 . If operation is not as specified, go to step  14 .
  13. Turn ignition off. On models equipped with 3-speed automatic or manual transmission, connect a fused jumper wire (backprobe) between ground and terminal No. 18 (Green/Red wire) at 22-pin PCM harness connector. On models equipped with 4-speed automatic transmission, connect a fused jumper wire (backprobe) between ground and terminal No. 11 (Green/Red wire) at 12-pin PCM harness connector. Turn ignition on. Blow into port "A" of solenoid. See Fig 2 . Air should flow from port "C" and not from port "B". If operation is as specified, go to step  17 . If operation is not as specified, go to next step.
  14. Turn ignition off. Disconnect EGR system check solenoid harness connector. Using DVOM, measure resistance between solenoid terminals. Resistance should be 37-44 ohms at 68°F (20°C). If resistance is as specified, go to next step. If resistance is not as specified, replace EGR system check solenoid and retest system.
  15. Disconnect vacuum hoses from EGR system check solenoid. Blow into port "A". See Fig 2 . Air should flow from port "B" and not from port "C". If operation is as specified, go to next step. If operation is not as specified, replace EGR system check solenoid and retest system.
  16. Using fused jumper wires, connect 12-volt source to EGR system check solenoid terminals. Blow into port "A". See Fig 2 . Air should flow from filter and not from port "B". If operation is as specified, check EGR system check solenoid harness for an open or short. Repair as necessary and go to next step. If operation is not as specified, replace EGR system check solenoid and retest system. Connect EGR system check solenoid vacuum valve harness connector and vacuum hoses securely.
    CAUTION: Make sure there are proper connections to MDF terminals because wrong terminal connection will cause damage to MDF sensor.
  17. Disconnect manifold differential pressure (MDP) sensor vacuum hose from filter and harness connector. Remove MDP sensor. Connect 3 new 1.5 volt batteries in series. Using fused jumper wires, connect positive to "Vin" terminal, and negative to "Ground" terminal of MDP sensor. See Fig 3 . Using DVOM, measure voltage between "Vout" and "Ground" terminals. Connect a hand-held vacuum pump to MDP sensor. As vacuum is applied, voltage reading should decrease. See MDP SENSOR VOLTAGE  table. If voltage is as specified, replace PCM and retest system. If voltage is not as specified, replace MAP sensor and retest system. Install MDP sensor. Connect vacuum hose and MDP harness connector securely.
Fig 3: Testing MDP Sensor
G96G09881Courtesy of SUZUKI OF AMERICA CORP.
MDP SENSOR VOLTAGE

Applied Vacuum: In. Hg (mm Hg) Output Voltage
7.9 (200) 2.40-4.40
9.8 (250) 2.13-4.13
11.8 (300) 1.86-3.86
13.8 (350) 1.59-3.59
15.7 (400) 1.32-3.32
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