Troubleshooting

Fig. 68 Vacuum & voltage chart.:

Fig. 72 Vacuum & voltage chart.:

VACUUM IS AVAILABLE FOR CONDITION 1

1. Check vacuum hose routing and correct as necessary.
2. If vacuum is still available, replace EGR control valves A and B.

NO VACUUM IS AVAILABLE FOR CONDITIONS 2 AND 3

1. Check for voltage at EGR control solenoid valve A under conditions 2 and 3.
2. If there is voltage, check EGR control solenoid valve A wiring circuit.
3. If there is no voltage, disconnect hose No. 15 from EGR control solenoid valve A.
4. Run engine at 4500 RPM and check for vacuum at hose No. 15.
5. If there is no vacuum, check vacuum hose routing and carburetor port. Correct as necessary and repeat test.
6. If there is vacuum, replace EGR solenoid valve A and repeat test.

VOLTAGE IS AVAILABLE & VACUUM IS GREATER THAN 2.8 IN. HG. FOR CONDITION 3

1. Replace EGR control solenoid valve B.

NO VOLTAGE IS AVAILABLE FOR CONDITIONS 1, 3 & 4 OR VOLTAGE IS AVAILABLE FOR CONDITION 2

1. Check wiring circuit of EGR control solenoid valve B.

VACUUM IS AVAILABLE FOR CONDITION 4

1. Check for voltage at EGR control solenoid valve A.
2. If there is voltage, replace EGR solenoid valve A.
3. If there is no voltage, check wiring circuit of EGR control solenoid valve A.

CHECKING WIRING CIRCUIT FOR EGR CONTROL SOLENOID VALVE A (YELLOW/WHITE WIRE)

1. Test control switch as follows:
a. Push voltmeter positive probe into gray wire terminal at emission control box No. 1 connector and connect negative probe to suitable ground.
b. Start engine and check for voltage during deceleration.
c. If there is no voltage, disconnect vacuum hose No. 2 from emission control box No. 1 and check for vacuum.
d. If there is no vacuum, check vacuum line for leaks, blockage, or loose connection. Correct as necessary and repeat test.
e. If there is vacuum, check vacuum line for leaks in emission control box No. 1.
f. If vacuum line is satisfactory, replace control switch and repeat test.
2. Test thermosensor as follows:

NOTE: The thermosensor must be tested for resistance twice in order to confirm proper operation; once in cold engine condition and then in hot engine condition.
a. Ensure that engine is cold by disconnecting hose No. 19 from charcoal canister. There must be no vacuum at idle.
b. Disconnect connector at control unit.
c. Check for resistance between blue/yellow and white/black terminals. Resistance should be above 1k ohm.
d. Run engine until it reaches operating temperature, then check resistance again. Resistance should be approximately 200 ohms.
e. If resistance is not within specifications, replace thermosensor and repeat test.
f. If ohmmeter shows no continuity, check wiring.
g. If wiring is satisfactory, replace thermosensor and repeat test.
3. Turn ignition switch on and check for voltage at black/yellow wire at control unit connector. If there is no voltage, check wiring.
4. Ensure that there is continuity for black wire between control unit and repeat test.

CHECKING WIRING CIRCUIT FOR EGR CONTROL SOLENOID VALVE B (PINK WIRE)

1. On vehicles with manual transmission, test 30 mph sped sensor as outlined under "Speed Sensor, Test" procedure.
2. On vehicles with automatic transmission, test vacuum switch A as follows:
b. apply vacuum to vacuum switch and check for voltage at vacuum switch.
c. Voltage should be available under conditions show, Fig. 72.
d. If there is no voltage, replace vacuum switch A and repeat test.
3. On vehicles with automatic transmission, turn ignition switch on and check for voltage at blue wire at control unit connector. If there is no voltage, check blue wire between ignition coil and control unit.
4. On vehicles with automatic transmission, test or 15 mph speed sensor as outlined under "Speed Sensor, Test" procedure.
5. Perform steps 2 through 4 under "Checking Wiring Circuit For EGR Control Solenoid Valve A".
6. If no faults are found in steps 1 through 5, replace control unit and repeat test.