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Oxygen Sensor after Catalytic Converter, Checking







Oxygen Sensor after Catalytic Converter, Checking

Observe all safety precautions: => [ Safety Precautions ] Generic Scan Tool

View clean working conditions: => [ Clean Working Conditions ] Clean Working Conditions

Prior to repair work, perform a preliminary check to verify the condition. Refer to => [ Preliminary Check ] Preliminary Check.

Use only gold-plated terminals when servicing any component with gold-plated electrical harness connector terminals.

For wiring diagrams, component locations, and connector views, Refer to the applicable wiring diagram.

Special tools, testers and auxiliary items required

Generic scan tool

Multimeter

Wiring diagram

Test requirements

The oxygen sensor properly installed

Exhaust system free of leaks

The oxygen sensor fuses OK

Ground connections between engine/transmission/chassis OK

Battery voltage at least 12.5 volts

Coolant temperature at least 80° C

All electrical consumers switched off

Vehicles with automatic transmission, shift selector lever in park or neutral

A/C switched off

Engine running

The oxygen sensor compares the oxygen content of the outside air with the residual oxygen content in the exhaust gas, and generates a voltage input signal to the engine control module.

If oxygen sensor voltage does not fluctuate, the sensor does not respond, or responds too slowly, the following causes are possible:

Slits in the oxygen sensor tip are plugged

Sensor not up to operating temperature

Sensor has been thermally overloaded

Transition resistance in signal wire or reference ground connection

Sensor has been damaged by electrical contact cleaner or similar contaminant (drawn through signal wire by capillary action due to thermal fluctuation)

Sensor has been damaged by exposure to silicone. When using silicone sprays and sealants, silicone residue is drawn into the engine where it passes unburned into the exhaust and can damage the oxygen sensor

Test procedure

- Using a generic scan tool, refer to Diagnostic Mode 05 - Read Current System Data.

Mode 05 may not be supported on all systems. On systems where Diagnostic Mode 05 is not supported, refer to Diagnostic Mode 6 for oxygen sensor monitoring test results.

- Review the mode data test results.

If any of the test results indicate a monitor failure:

- Refer to the monitor support documentation as indicated in the mode test procedure to diagnose and repair the cause of the failure.

If the test results indicate no monitor failures:

Checking primary voltage

- Disconnect the oxygen sensor electrical harness connector. Refer to the service manual for removal and installation procedures.

- Switch ignition on.

- Using a multimeter, measure the voltage between the sensor signal and reference ground circuits.

Specification: 0.400 to 0.500 V

- Switch ignition off.

If specified value is not obtained:

- Check the oxygen sensor wiring and connections.

If specified value is obtained:

- Replace the oxygen sensor. Refer to the appropriate service manual for removal and installation procedures.

Checking wiring and connections

- Remove the engine control module. Refer to the service manual for removal and installation procedures.

- Using a multimeter, measure the resistance of the signal and reference ground circuits between the oxygen sensor and the engine control module. Refer to the applicable wiring diagram.

Specified value: 1.5 ohms max.

If the specification was not obtained:

- Check the circuits for a short to each other, short to battery voltage, and short to ground.

- Check the electrical harness connector for damage, corrosion, loose or broken terminals.

- Repair the wiring or connection as necessary.

If no malfunction is detected in the wiring:

- Replace the engine control module. Refer to the service manual for removal and installation procedures.

Final procedures

After repair work, the following work steps must be performed in the following sequence:

1. Check the DTC memory. Refer to => [ Diagnostic Mode 03 - Read DTC Memory ] Diagnostic Modes 01 - 09.

2. If necessary, erase the DTC memory. Refer to => [ Diagnostic Mode 04 - Erase DTC Memory ] Diagnostic Modes 01 - 09.

3. If the DTC memory was erased, generate readiness code. Refer to => [ Readiness Code ] Readiness Code.