- Check all vacuum hose to make sure they are tight and not leaking.
- Run the engine to normal operating temperature.
- Disconnect the vacuum hose from the 1st EGR control valve and check that
the engine continues to run smoothly. If not, replace the valve.
- Connect a vacuum gauge to the hose and increase the engine speed to 2,500
rpm. The gauge should read at least 5.9 in.Hg. If not, check the water thermovalve,
water temperature switch, No.1 EGR solenoid valve and, on trucks with manual
transmission, the No.2 EGR vacuum switch.
- Disconnect the vacuum hose from the 2nd EGR control valve and see that the
engine continues to run smoothly. If not, replace the valve.
- Connect a vacuum gauge to the hose and increase the engine speed to 2,500
rpm. The gauge should read at least 5.9 in.Hg. If not, check the No.2 EGR
solenoid valve and the No.1 EGR vacuum switch.
- Disconnect the hose from the EGR modulator valve and plug it.
- Connect a length of hose to the port of the EGR modulator valve.
- Increase the engine speed to 2,500 rpm and blow into the hose. See if the
vacuum reading increases. If not, replace the valve.
- Reconnect all hoses.
- Start the engine and run it at idle speed. Apply vacuum to the valve. Check
that the engine runs rough or stalls when 1.58 in.Hg of vacuum is applied
to the valve.
- If the engine does not behave as described with the specified amount of
vacuum applied, replace the control valve.
- Start the engine and run it at idle speed. Apply vacuum to the valve. Check
that the engine runs rough or stalls when 2.76 in.Hg of vacuum is applied
to the valve.
- If the engine does not behave as described with the specified amount of
vacuum applied, replace the control valve.
- The sensor is located on top of the EGR valve. Remove the rubber boot from
the connector at the EGR valve.
- Disconnect the vacuum hose from the EGR valve and connect a hand vacuum
pump.
- Turn the ignition switch ON. Using a voltmeter, check the voltage at each
terminal in the harness side of the connector.
- With no vacuum applied:
- Terminal A (B/L) — 0.7 volts
- Terminal B (B/LG) — less than 1.5 volts
- Terminal C (G/Y) — 4.5-5.5 volts
- With vacuum applied:
- Terminal A (B/L) — 4.7 volts
- Terminal B (B/LG) — less than 1.5 volts
- Terminal C (G/Y) — 4.5-5.5 volts
- If the voltage is incorrect for terminals B and C,
check the wiring harness and ECU terminals 1D, 1F and 1G.
- If incorrect at terminal A. check the resistance of the sensor,
then the wiring harness and then the ECU.
- Check the resistance between the terminals while applying 0-5.9 in. Hg of
vacuum to the EGR valve:
- Terminals B and C — 5
k
- Terminals A and C — 0.0-5.5
k
- Terminals A and B — 0.7-6.0
k
- Disconnect the vacuum hoses from the solenoid valve. Label the hoses for
reinstallation.
- Blow air through the vent hose and air should flow.
- Disconnect the solenoid valve connector.
- Connect 12 volts to one terminal of the solenoid valve and ground the other.
- Blow air through the solenoid valve and verify that air does not flow.
- Replace the duty solenoid valve if it does not perform as specified.
- Blow air through the vacuum hose and verify that the air does not flow.
- Connect 12 volts to one terminal of the solenoid and ground the other.
- Blow air through the vacuum hose and verify that the air flows through.
If not as specified, replace the valve.
- Note the routing of all hoses leading to the modulator valve, especially
the hose which is connected to the exhaust side of the EGR valve. Remove the
EGR Modulator valve. Plug the No. 1 port and then attach a source of vacuum
to the No. 3 port.
- Attach a clean hose to the exhaust gas port. Blow into the end of the hose
and maintain pressure. Apply vacuum to the No. 3 port and then seal off the
source of vacuum. Vacuum should be maintained as long as air pressure is applied.
- Stop applying air pressure. The vacuum should be released. If the valve
fails to respond properly in either Step 2 or 3, replace it.