EGR Function Testing - General Motors Cars Chevrolet Camaro II

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, EGR valve is defective. Place transmission in Park or Neutral and start engine.
3. With engine running at normal operating temperature, push up on diaphragm. Engine RPM should decrease. If RPM decreases, EGR valve is functioning properly. Connect vacuum gauge to EGR valve vacuum supply hose. Raise engine speed to 2000 RPM and ensure adequate vacuum supply to EGR valve exists.

Negative Backpressure EGR Valve

1. EGR negative backpressure valve may be identified by letter "N" in last position of EGR part number. With engine off, disconnect EGR valve vacuum signal hose. Connect vacuum pump to vacuum signal tube and apply 10 in. Hg.
2. EGR diaphragm should move up and remain up for 20 seconds. If diaphragm does not stay up for 20 seconds, EGR valve is defective. 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.

Positive Backpressure EGR Valve

1. EGR positive backpressure valve may be identified by the letter "P" in the last position of the EGR part number. To test EGR valve, place transmission in Park or Neutral.
2. Set parking brake and block drive wheels. Connect tachometer. With engine running and at normal operating temperature, increase engine speed to 2000 RPM.
3. 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 by-passed.
4. 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.
5. If engine RPM changes and EGR diaphragm moves, EGR valve is functioning correctly. If engine RPM does not change and diaphragm does not move, remove EGR valve and apply 10 in. Hg to EGR vacuum signal tube. EGR valve should not open.
6. 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.
7. 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.
8. With vacuum present at signal tube, EGR valve should open while pressure is applied and should close when no vacuum is present.

1983-84 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 decreasing from 2000 RPM to idle. EGR valve diaphragm should not move. 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.

1985 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.

1986 Pulse-Width Modulated EGR Valve

2.8L

The EGR valve is controlled by a normally closed solenoid (allows vacuum to pass when energized). The ECM energizes the solenoid to turn the EGR on and monitors vacuum to the EGR with the EGR diagnostic switch. Code 32 will detect a faulty solenoid, vacuum switch or vacuum supply.

Note. Test numbers refer to test numbers on diagnostic chart.

1. With the ignition on and engine stopped, the solenoid should not be energized and vacuum should not pass to the EGR valve.
2. Grounding the diagnostic terminal will energize the solenoid and allow vacuum to pass the valve.
3. Checks for plugged EGR passages. If passages are plugged, the engine may have severe detonation on acceleration.
4. The EGR solenoid will not be energized in Park or Neutral. This will determine if the Park/Neutral switch input is being received by the ECM.

Flow Chart C7A, EGR Check (2.8L). Scheme 3

Flow Chart C7A, EGR Check (2.8L, 1 Of 2). Scheme 4

Flow Chart C7A, EGR Check (2.8L, 2 Of 2). Scheme 5

5.0/5.7L

The EGR valve is controlled by a normally open pulse width modulated solenoid (PWM). The ECM turns the solenoid off to allow vacuum to pass to the EGR and turns the solenoid on to prohibit EGR operation. When EGR is commanded, the solenoid is turned on and off many times a second (duty cycle).

The duty cycle is calculated by the ECM based on information from the coolant, MAT, TIPS and MAF sensors. Also, engine RPM and the Park/Neutral switch inputs affect EGR. There is no EGR when in Park or Neutral and TPS is below a calibrated value or TPS is indicating wide open throttle (WOT). With the ignition on and engine stopped, the EGR solenoid is de-energized. The solenoid, however, should be energized if the diagnostic terminal is grounded with the ignition on and engine not running.

Note. Test numbers refer to test numbers on diagnostic chart.

1. This will test the solenoid value to determine if it is capable of closing off the manifold vacuum from the EGR valve. The vacuum may bleed off slowly but this should not be considered a fault.
2. As soon as back pressure is available at the EGR valve, the bleed portion in the valve should open and cause the valve to go to its heated position.
3. The EGR valve will be inoperative if the Park/Neutral switch is misadjusted or defective. Use "SCAN" tester and check Park/Neutral switch.

Flow Chart C7B, EGR Recirculation Check (5.0/5.7L). Scheme 6

Note. Before using this chart, check for ported vacuum to EGR solenoid, also check hoses for leaks and restrictions. Should be at least 7" Hg vacuum at 2000 RPM. This chart assumes there is no Code 32.

Flow Chart C7B, EGR Recirculation Check (5.0/5.7L). Scheme 7

1987 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.

1988 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.

TEST 9

Note. A Tech 1 scan tool or a tester capable of cycling ECM output devices may also be used to perform EGR function test.

1988-1992 3.1L, 3.4L & 3.8L (Digital EGR Valve)

1. Turn engine off. Disconnect EGR valve electrical connector. Start engine and allow engine to idle. Using a 12-volt power source and a fused jumper wire, apply voltage to terminal "D" of EGR valve. (Scheme 8) NOTE: EGR valve wire colors may vary.
2. Using a jumper wire with one end connected to a good ground, alternately touch remaining end of jumper wire to EGR valve terminals "A", "B", and then "C". Engine RPM should change as each EGR valve terminal is contacted. If engine RPM changes, EGR valve is functioning correctly.
3. 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, EGR valve is defective.

Scheme 8

1990-91 - 2.3L "W" Body VIN D (Digital EGR Valve)

1. Turn engine off. Disconnect EGR valve electrical connector. Start engine, and allow it to idle. Using a 12-volt power source and a fused jumper wire, apply voltage to terminal "B" of EGR valve. (Scheme 9) Using a jumper wire connected to a good ground, alternately touch remaining end of jumper wire to EGR valve terminal "A" and then to terminal "C".
2. Engine RPM should change as each EGR valve terminal is contacted. If engine RPM changes, EGR valve is functioning correctly. 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, EGR valve is defective.

Scheme 9

1988 2.8L "W" Body (Integrated Electronic EGR Valve)

The integrated electronic EGR valve functions similarly to a port valve with a remote vacuum regulator. The built-in solenoid is normally open, which causes the vacuum signal to be vented off to the atmosphere when EGR is not being commanded by the ECM. The ECM controls EGR flow with a pulse width modulated signal (turns on and off many times a second). This controls the amount of vacuum vented to atmosphere and controls amount of vacuum applied to the diaphragm. The electronic EGR valve also contains a voltage regulator, which regulates current to the solenoid to provide different amounts of EGR flow. The EGR valve also contains a pintle position sensor, which works similarly to a TPS sensor. As EGR flow is increased, the sensor output also increases.

Note. Test numbers refer to test numbers on diagnostic chart.

1. Whenever the solenoid is de-energized, the solenoid valve should be closed. This should not allow the vacuum to move the EGR diaphragm. If the filter is plugged, however, the vacuum applied with the hand held vacuum pump will cause the diaphragm to move because the vacuum will not be vented to the atmosphere.
2. This test will determine if the EGR filter is plugged, or if the EGR valve itself is faulty. Use care when removing the filter to avoid damaging the EGR assembly.
3. If the valve moves in this test, it is due to circuit No. 435 being shorted to ground.
4. Grounding the diagnostic "test" terminal should energize the solenoid which closes off the vent and allows vacuum to move the diaphragm.
5. The EGR assembly is designed to have some leakage, therefore, 7 in. Hg of vacuum is all that should be held. However, if too much of a leak exists (less than 4 in. Hg of vacuum holding), the assembly is leaking excessively and must be replaced.

Integrated Electronic EGR Valve

1. Turn engine off. Connect vacuum pump to EGR valve. Apply vacuum and observe EGR valve. EGR valve should not move. If valve moves, check vent filter for restriction. 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, system is malfunctioning.

4.5L

1. Place transmission in Park or Neutral. Set parking brake and block drive wheels. Connect tachometer. With engine running at normal operating temperature, ensure fast idle speed is set to specifications.
2. Run engine at 2000 RPM. 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 solenoid, the EGR vacuum is locked out in Park/Neutral and solenoid must be by-passed.
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 did change and EGR diaphragm moved, the EGR valve is functioning properly. If engine RPM did not change and diaphragm did not move, remove EGR valve and apply 10 in. Hg vacuum 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 or air (15 psi maximum) into valve seat. EGR valve should open completely.
6. If air is not available, remove EGR valve. 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.

4.6L

Use CHART C-1 for EGR function testing. (Scheme 10)

Scheme 10

3.1L, 3.4L & 3.8L (Digital EGR Valve)

Start engine. Using Tech 1 scan tool or a tester capable of cycling ECM output devices, select miscellaneous tests. With engine idling, RPM should drop and engine should idle rough as each solenoid is energized. If system operates as specified, EGR valve is functioning correctly.

Linear EGR Valve

A malfunction in EGR circuit will set a related trouble code, see appropriate SELF-DIAGNOSTICS article in ENGINE PERFORMANCE section of electronic information product.

Metro

1. With engine cool, ensure EGR valve is not loose or broken. Replace as necessary. Start engine and warm to normal operating temperature.
2. Place finger on bottom of EGR valve diaphragm. Increase engine speed. EGR valve diaphragm should move. If diaphragm does not move, allow engine to idle. Disconnect vacuum hose from EGR valve. (Scheme 11)
3. Apply 8 in. Hg of vacuum to EGR valve and place finger on diaphragm. Vacuum should hold, diaphragm should move and engine should run rough and may stall. If EGR valve operation is as specified, go to next step. If EGR valve operation is not as specified, replace EGR valve.
4. Check for carbon in valve which may cause a restriction. Restriction may be small enough so that engine may not stall, but large enough to cause DTC P0400 to set.

Scheme 11

TEST 17

For EGR testing, see appropriate ENGINE PERFORMANCE section of electronic information product.