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DTC P0400 - Exhaust Gas RECIRCULATION (EGR) Flow Malfunction

NOTE: Vehicle speed input must be received by PCM for proper EGR operation. While testing EGR, leave transmission in Neutral with engine running. Block one rear wheel and rotate other rear wheel forward by hand.
  1. Raise and support vehicle. Place transmission in Neutral. Start engine. Increase engine RPM and ensure EGR valve DOES NOT operate with coolant temperature less than 131°F (55°C). Go to next step.
  2. Allow engine to reach normal operating temperature. Increase engine RPM and observe EGR diaphragm. If diaphragm moves, go to next step. If diaphragm does not move, disconnect vacuum hose from EGR valve. Using a hand-held vacuum pump, apply vacuum to EGR valve. If EGR valve opens and holds vacuum, go to step 4). Replace EGR valve if it does not open or hold vacuum. Retest system.
  3. Using a shop towel or glove, open EGR valve by hand with engine running. Engine should idle rough or stall. If idle does not change, remove EGR valve and clean EGR passage. Retest system.
  4. Check EGR pressure transducer filter for contamination. Clean if necessary. If filter is okay, go to next step.
  5. Remove EGR pressure transducer. Plug one vacuum port with finger and blow into remaining vacuum port. Air should pass freely through filter. Connect a hand-held vacuum pump 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. Replace EGR pressure transducer if operation is not as specified. Retest system.
  6. Reconnect EGR pressure transducer. Disconnect vacuum hoses from EGR solenoid vacuum valve. Turn ignition on. Blow into port "A". See Fig 1 . Air should pass through port "B" and not from filter. Start engine and let idle. Blow into port "A". Air should pass through filter and not port "B". If operation is as specified, go to step 9). If operation is not as specified, go to next step.
    Fig 1: Identifying EGR Solenoid Vacuum Valve Ports
    G96I09877Courtesy of SUZUKI OF AMERICA CORP.
  7. Turn ignition off. Disconnect EGR solenoid vacuum valve harness connector. Using an ohmmeter, measure resistance at solenoid 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.
  8. Disconnect vacuum hoses from solenoid. Blow into port "A". See Fig 1 . Air should pass through port "B" and not from filter. Using fused jumper wires, connect a 12-volt battery to solenoid terminals. Blow into port "A". Air should pass through filter and not port "B". If operation is as specified, check EGR solenoid vacuum valve harness for open or short. Repair as necessary. If operation is not as specified, replace EGR solenoid vacuum valve. Retest system.
  9. Disconnect vacuum hoses from EGR system check solenoid. See Fig 2 . Turn ignition on. Blow into port "A". Air should pass through port "B" and not port "C". If operation is as specified, go to step 14). If operation is not as specified, go to next step.
    Fig 2: Identifying EGR Check Solenoid Ports
    G96C09879Courtesy of SUZUKI OF AMERICA CORP.
  10. Turn ignition off. Using a fused jumper wire, backprobe PCM harness connector "C", terminal No. 18 (Green/Red wire) to ground. See Figure . Turn ignition on. Blow into port "A" of solenoid. Air should pass through port "C" and not port "B". If operation is as specified, go to step 14). If operation is not as specified, go to next step.
  11. Turn ignition off. Disconnect EGR system check solenoid harness connector. Using an ohmmeter, 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. Retest system.
  12. Disconnect vacuum hoses from EGR system check solenoid. Blow into port "A". Air should pass through port "B" and not port "C". If operation is as specified, go to next step. If operation is not as specified, replace EGR system check solenoid. Retest system.
  13. Using fused jumper wires, connect a 12-volt battery to solenoid terminals. Blow into port "A". Air should pass through filter and not port "B". If operation is as specified, check EGR system check solenoid harness for open or short. Repair as necessary. If operation is not as specified, replace EGR system check solenoid. Retest system.
  14. Disconnect MAP sensor vacuum hose and harness connector. Remove MAP sensor. Connect three 1.5 volt batteries in series. Using fused jumper wires, connect positive to "Vin" terminal, and negative to "Ground" terminal of MAP sensor. See Fig 3 . Using a voltmeter, measure voltage between "Vout" and "Ground" terminals. Connect a hand-held vacuum pump to MAP sensor. As vacuum is applied, voltage reading should decrease. See the MAP SENSOR VOLTAGE table below. If reading is not as specified, replace MAP sensor. Retest system.
Fig 3: Identifying MAP Sensor Terminals
G96G09881Courtesy of SUZUKI OF AMERICA CORP.
MAP 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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