Function Check

°�Fig. 2 Lambda-sond (oxygen sensor) system wiring diagram:

Fig. 6 Removing electronic control module electrical connector cover:

Fig. 7 Connecting test light between electrical connector terminal 8 and ground:

Fig. 8 Connecting test light between electrical connector terminal 8 and 5:

Fig. 9 Connecting test light between blue wire electrical connector pin and ground:

Fig. 10 Connecting test light to both electrical connection pins:

Fig. 11 Connecting ohmmeter to frequency valve:

Fig. 12 Disconnecting electrical connector from pressure differential switch:

1. Disconnect electrical connector from oxygen sensor.
2. Connect a suitable dwell meter to test point red wire, Fig. 2. Dwell meter must have a measuring range of at least 70°. Set dwell meter to 4 cylinder engine range for this test.
3. Disconnect electrical connector from ignition control unit. Connect test relay No. 5170 or equivalent, to ignition control unit and turn ignition on.
4. Note dwell meter reading and listen to frequency valve.
5. If frequency valve does not buzz and dwell meter indicates 0, note the following:
a. Turn ignition switch off. Disconnect electrical connector from control unit and remove electrical connector cover, Fig. 6.
b. Turn ignition switch on and connect a test light between electrical connector terminal 8 and ground, Fig. 7. Test light should come on. If not, check relay. If relay is good, check wiring.
c. Connect test light between electrical connector terminals 8 and 5, Fig. 8. Test light should come on. If test light does not come on, check for broken wire.
d. Connect test light between electrical connector terminals 8 and 16, Fig. 8. Test light should come on. If test light does not come on, check for broken wiring. If wiring is good, conduct test with a new control unit.
6. If frequency valve does not buzz but dwell meter needle deflects, note the following:
a. Connect a test light between blue wire electrical connector pin and ground, Fig. 9. Test light should come on. If not, check for a broken frequency valve wire.
b. Connect test light to both electrical connector pins, Fig. 10. Test light should light and light intensity should be dim. If test light does not light, control unit or wiring to control unit is defective.
c. Connect an ohmmeter to frequency valve, Fig. 11. Measure frequency valve resistance. Resistance should be 2-3 ohms. If not, replace frequency valve.
7. If frequency valve buzzes but dwell meter indicates 0, check for a broken test point wire.
8. If frequency valve buzzes but dwell meter reading is high, note the following:
a. Disconnect electrical connector from pressure differential switch, Fig. 12. If dwell meter reading decreases, replace switch. If not, connect pressure differential switch electrical connector.
b. Turn ignition switch off. Disconnect electrical connector from control unit and remove electrical connector cover.
c. Turn ignition switch on and connect test light between electrical connector terminals 8 and 11. Test light should remain off. If test light comes on, check for a short circuit.
d. Connect an ohmmeter between electrical connector terminals 2 and 4. Resistance should be infinity. If not, conduct this test with a new control unit.