Bosch

TESTING PROCEDURE:

NOTE: While trouble shooting, always check the wiring, fuses and connectors for good condition and routing. Use the wiring diagrams found in CHASSIS ELECTRICAL DIAGRAMS to supplement your testing efforts.

Color Code Legend:

Checking ECU Ground Connections:

1. Turn ignition OFF.
2. Access fuel injection ECU by removing the passenger side kick panel and glove compartment.
3. Check fuel injection ECU ground connections. They should make good contact and fit tight.

Removing ECU Connector:

4. Remove fuse #1 (located in central electric unit behind ash tray) to interrupt the power supply. Then remove the ECU connector by pressing up the latch and folding out the wire cluster.

Removing Protective Sleeve:

5. Remove connector protective sleeve and reinstall fuse #1 for testing.
CAUTION: ^ Never check connections from the front. Connectors can get damaged and worsen the problem.
^ Check connections through the holes in the connector.
^ Connection pin numbers are printed on the connector side.

Checking Pink Wire At Oxygen Sensor (Lambda Sond) Connector:

6. To check the oxygen sensor (lambda sond) pre-heating element, connect a lead between pin 20 and 21 (at ECU connector) to ground.
7. Connect a voltmeter between ground and terminal #1 (pink wire) at the two prong oxygen sensor connector, located at the firewall near the A/C receiver/dryer.

Reading: approx. 12 volts

a. If reading is O.K., proceed with next step.
b. If reading is incorrect, check wiring to system relay (located next to fuel injection ECU) and check fuse #11 (located behind ash tray). If fuel pumps are operating (you should be able to hear them), system relay is in good working order. If fuel pumps can not be heard, check system relay (see SYSTEM RELAY). Repair as needed and retest.
8. Remove voltmeter and ground lead from pin 20.

Checking Resistance At Oxygen Sensor (Lambda Sond) Heating Element:

9. Connect an ohmmeter between ground and terminal #1 (pink wire) at the two prong oxygen sensor connector.
a. With sensor cold (68°F or 20°C):

Reading: approx. 2 - 3 ohms

b. With sensor hot (over 660°F or 350°C which is the temperature of the sensor when the engine is hot during idle):

Reading: approx. 7 - 14 ohms

10. If reading is correct, heating element is O.K., proceed with step 13.
If reading is incorrect, proceed with next step.

Checking Oxygen Sensor (Lambda Sond) Ground Connection:

11. Connect an ohmmeter between ground and terminal #2 (black wire) at the two prong oxygen sensor connector.

Reading: 0 ohm

a. If reading is correct, replace and retest with new oxygen sensor (lambda sond).
b. If reading is incorrect, repair wire or connector leading to ground and retest.
12. Disconnect ground lead from pin 21 and ohmmeter.

Reconnecting The ECU Connector:

13. Remove the #1 fuse and reconnect the ECU connector. Ensure that the rubber seal in the connector is installed before it is connected to the ECU.
14. Reinstall the #1 fuse.

Connecting CO-Meter:

15. Connect a CO-meter to the test port in the exhaust system. Use VOLVO tool #5410 or equivalent to access the test port.
16. Run engine to operating temperature.
17. Check CO content at idle.

CO should be: 0.4 - 0.8%

Disconnecting Oxygen Sensor Lead:

18. Separate the oxygen sensor (lambda sond) connector.
a. If the CO level drops below 0.4%, check intake system for air leaks and repair as necessary.
b. If the CO level rises above 0.8%, check fuel injectors for fuel leaks and check fuel system pressure (see FUEL SYSTEMS), repair as necessary.

Checking Oxygen Sensor With A 1.5V Battery:

19. If the CO level is normal, disconnect the negative battery terminal to reset the adaptive system. Reconnect battery terminal.
20. Recheck CO content.
21. Apply 1.5 volts to the lead coming from the fuel injection ECU using a battery.
a. The CO content should now fall, indicating correct operation of the ECU and wiring.
b. If the CO content does not fall, fault lies in the wiring or the ECU. Check wiring and repair as needed.

Checking ECU:

22. Ground lead to ECU.
a. The CO content should now rise, indicating correct operation of the ECU and wiring.
b. If the CO content does not rise, fault lies in the wiring or the ECU. Check wiring and repair as needed.

Reconnecting Oxygen Sensor Connector:

23. Reconnect oxygen sensor connector. Wait three (3) minutes for the adaptive system to adjust the fuel injection timing duration.

Checking Oxygen Sensor:

24. Disconnect the oxygen sensor plug and connect a voltmeter to the wire from the sensor.

The voltmeter needle should average: 0.5 volts with correct CO content (0.4 - 0.8%)

This will show that the oxygen sensor is operating correctly.
If oxygen sensor fails this test, replace and retest with new sensor.
25. Reconnect the oxygen sensor connector. Let engine run for three (3) minutes and recheck the CO content.

CO should be: 0.4 - 0.8%

26. If vehicle passes all tests and CO is not within specifications (0.4 - 0.8%), fault may be an other faulty component (injector, ECU... ).