Ground Circuit inspection
1.

Ignition "OFF"

2.

Disconnect HO2S connector, and ECM connector.

3.

Measure resistance between terminals 2 of the HO2S harness connector and 20 of the ECM harness connector.

Specification : Approx. 0Ω

4.

Is resistance within the specification?

YES

▶ Go to "Signal Circuit Inspection" procedure.

NO

▶ Repair open in the ground circuit and go to "Verification of Vehicle Repair" procedure

Signal Circuit Inspection
1.

Measure resistance between terminals 1 of the HO2S harness connector and 14 of the ECM harness connector.

1)

Specification : Approx. 0Ω

2.

Is resistance within specifications?

YES

a.

Go to "Heater Circuit Inspection" procedure

NO

a.

Repair open or short in the signal circuit and go to "Verification of Vehicle Repair" procedure

Heater Circuit Inspection
3.

Check for power circuit harness

(1)

Recnnect ECM connector.

(2)

Ignition "ON" ＆ Engine "OFF".

(3)

Measure voltage between terminal 3 of the HO2S heater harness connector and chassis ground.

1)

Specification : Approx. B+

(4)

Is voltage within specifications?

YES

a.

Go to next step as below.

NO

a.

Check for an open in the power circuit between the main relay and the HO2S.

b.

Especially check for "20A ECU #1 fuse" is installed and not blown.

c.

Repair as necessary and go to "Verification of Vehicle Repair" procedure

4.

Check for open in control harness

(1)

Ignition "OFF"

(2)

Disconnect ECM connector.

(3)

Measure resistance between terminals 4 of the HO2S heater harness connector and 1 of the ECM harness connector.

1)

Specification : Approx. 0Ω

(4)

Is resistance within the specification?

YES

a.

Go to next step as below.

NO

a.

Repair as necessary and go to "Verification of Vehicle Repair" procedure.

5.

Check for short to ground in control circuit

(1)

Measure resistance between terminal 4 of the HO2S heater harness connector and chassis ground.

1)

Specification : infinite

(2)

Is resistance within the specification?

YES

a.

Go to "Terminal and Connector Inspection" procedure

NO

a.

Repair open or short to ground in control circuit and go to "Verification of Vehicle Repair" procedure.

Terminal and Connector Inspection
1.

Many malfunctions in the electrical system are caused by poor harness(es) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.

Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

3.

Has a problem been found?

YES

▶ Repair as necessary and go to "Verification of Vehicle Repair" procedure.

NO

▶ Go to "Ground Circuit Inspection" procedure.

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