EGR Function Testing Chevrolet Camaro II

PULSE-WIDTH MODULATED EGR VALVE

1. Check vacuum lines for leaks and electrical connectors for proper installation. Place transmission in Park or Neutral. With engine idling at normal operating temperature, push up on underside of EGR valve diaphragm. Engine RPM should drop. If engine RPM does not drop, clean EGR valve and passages.
2. Check for EGR valve diaphragm movement with engine RPM change from 2000 RPM to idle. EGR valve diaphragm should not change. If EGR valve diaphragm moves with RPM change, check Park/Neutral switch for open circuit or misadjustment. If EGR valve diaphragm does not move, disconnect ALDL test connector and ground test terminal. If EGR valve diaphragm moves, EGR valve is functioning properly.
3. If EGR valve diaphragm still does not move, stop engine and disconnect EGR solenoid connector. Connect 12-volt test light to EGR solenoid connector terminals. Turn ignition on and ground ALDL test terminal. Test light should flash repeatedly.
4. If test light remains on steadily, check for short to ground in wire to ECM. If wire is okay, ECM is faulty. If test light flashes, go to step 5). If light is off, connect test light from each EGR connector terminal to ground. If light is off, repair open in wire from solenoid to ignition (including fuse). If light is on at both terminals, check for a short to voltage in wire to ECM terminal. NOTE: ECM may have been damaged from a short to voltage.
5. Repair and recheck. If light was on for one terminal, check for an open in wire to ECM. If wire is okay, check resistance of EGR solenoid. If EGR solenoid resistance is not over 20 Ohms, replace EGR solenoid and ECM. If resistance is over 20 Ohms, check for faulty ECM connection or ECM.
6. Check for vacuum at EGR solenoid at 2000-3000 RPM. If engine does not use a vacuum regulator, there should be at least 7 in. Hg at solenoid. If engine is equipped with a vacuum regulator, there should be 2-10 in. Hg.
7. If vacuum is greater than 10 in. Hg, replace regulator. If vacuum is less than 2 in Hg, vacuum at solenoid is okay. Check EGR solenoid connections and/or faulty EGR solenoid. To test EGR solenoid for all models except Cadillac, see appropriate EGR SYSTEM article in the ENGINE PERFORMANCE section. To test EGR solenoid for Cadillac models, see PERFORMANCE CHART 7 in DFI TESTS W/CODES article in the ENGINE PERFORMANCE section.

INTEGRATED ELECTRONIC EGR VALVE

1. With ignition off, connect vacuum gauge to EGR valve. EGR valve should not move. If EGR valve moves, ensure vent filter is unrestricted and replace EGR valve (if necessary).
2. Turn ignition on and repeat step 1). When applying vacuum, EGR valve should not move. If EGR valve moves, a fault exists in ECM or electrical circuits. If additional testing is required, see appropriate COMPONENT TESTING article in the EMISSION section.

PORTED EGR VALVE

1. Turn ignition off. Disconnect EGR vacuum hose at vacuum signal tube. Connect a hand-held vacuum pump to vacuum signal tube and apply 10 in. Hg. EGR diaphragm plate should move up and remain up for at least 20 seconds.
2. If diaphragm moves up and holds for 20 seconds, diaphragm is operating properly. If diaphragm does not hold vacuum, replace EGR valve. Place transmission in Park or Neutral and connect vacuum pump to EGR valve.
3. With engine running at normal operating temperature, push up on diaphragm. Engine RPM should decrease. If RPM decreases, EGR valve is functioning properly. If engine RPM does not decrease, replace EGR valve. If further testing is required, see the appropriate COMPONENT TESTING article in the EMISSION section.

DIGITAL EGR VALVE

1. Turn engine off. Disconnect EGR electrical connector. Using Tool Kit (J-35616), install jumper harness connector to EGR electrical connector terminal "D" to terminal "D" of EGR valve. Connect jumper to ground. Start engine. Engine RPM should change as each EGR valve terminal "A", "B" or "C" is contacted.
2. If engine RPM does not change, check for restriction in EGR supply tube or plugged EGR valve orifice. If EGR valve is not restricted or plugged, replace EGR valve. If engine RPM changes, EGR valve is okay. If further testing is required, see the appropriate COMPONENT TESTING article in the EMISSION section.

POSITIVE BACKPRESSURE EGR VALVE

1. Place transmission in Park or Neutral. Set parking brake and block drive wheels. Connect tachometer. With engine running at normal operating temperature and fast idle speed set to specification, run engine at 2000 RPM.
2. On carbureted engines, place fast idle cam on high step. Disconnect vacuum hose from EGR valve and plug hose. EGR valve diaphragm should move down and engine RPM should increase. NOTE: On some engines with ECM-controlled EGR control solenoid, EGR vacuum is locked out in Park/Neutral and EGR control solenoid must be bypassed.
3. Reconnect vacuum hose. Diaphragm should move up and engine RPM should decrease. A slight vibration of diaphragm plate may be noticed in backpressure EGR valves.
4. If engine RPM changes and EGR diaphragm moves, EGR valve is okay. If engine RPM did not change and diaphragm did not move, remove EGR valve and apply 10 in. Hg to EGR vacuum signal tube. EGR valve should not open.
5. If EGR valve opens, replace EGR valve. With vacuum still applied, direct a stream of air (15 psi maximum) into valve seat. EGR valve should open completely.
6. If air is not available, connect a section of hose over EGR valve seat. Connect a vacuum pump to signal tube. With thumb plugging intake port of EGR valve, operate vacuum pump while alternately blowing and pausing.
7. With vacuum present at signal tube, EGR valve should open while pressure is applied and should close when no vacuum is present. If further testing is required, see appropriate COMPONENT TESTING article in the EMISSION section.

NEGATIVE BACKPRESSURE EGR VALVE

1. With EGR valve in vehicle and engine off, disconnect EGR valve vacuum signal hose. Connect vacuum pump to vacuum signal tube and apply 10 in. Hg. EGR diaphragm should move up and remain up for 20 seconds.
2. If diaphragm does not stay up for 20 seconds, replace EGR valve. Using an assistant, again apply 10 in. Hg to signal tube. Have assistant immediately try to start engine. Observe diaphragm for movement.
3. If diaphragm moves to a seated position (valve closed) during cranking and initial starting, EGR valve is functioning properly. If diaphragm does not move, clean or replace EGR valve.
4. If EGR valve is not in vehicle, connect a short section of hose over EGR valve seat. Apply 10 in. Hg to vacuum signal tube. EGR valve should open. If EGR valve does not open, clean or replace EGR valve.
5. With vacuum still applied, plug intake port of valve with thumb. Apply suction to hose connected to EGR valve seat. EGR valve should close immediately. If further testing is required, see appropriate COMPONENT TESTING article in the EMISSION section.