Many malfunctions in the electrical system are caused by poor harness(s) and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
Check the following conditions:
Check for damaged harness and terminals: contact resistance, oxidation, bent or broken terminals.
Check for poor connection between ECM and component: backed out terminal, improper mating, broken locks or poor terminal to wire connection
Use a suitable male pin to ensure that contact in sockets is good. The pin should remain in position when pulled gently.
Has a problem been found?
YES
Repair as necessary and go to "Verification of Vehicle Repair" procedure
NO
System OK. Go to "Verification of Vehicle Repair" procedure
Turn ignition switch to OFF and disconnect HO2S(up) harness connector or HO2S(down) harness connector and ECM harness connector.
Measure Resistance of HO2S signal circuit between HO2S(up) harness connector and ECM harness connector.
Measure Resistance of HO2S signal circuit between HO2S(down) harness connector and ECM harness connector.
Probe(+) : HO2S(up) harness connector NO2 and HO2S(down) harness connector NO2.
Probe(-) : ECM harness connector NO18 and ECM harness connector NO55.
Specification: below 1Ω
Does each resistance indicate continuity circuit?
YES
Go to "OPEN CIRCUIT INSPECTION FOR HO2S TO GROUND"
NO
Open circuit between HO2S harness connector and ECM harness connector
Repair as necessary and go to "Verification of Vehicle Repair" procedure
Turn ignition switch to OFF and disconnect HO2S(up) harness connector or HO2S(down) harness connector and ECM harness connector.
Measure Resistance of HO2S ground circuit between HO2S(up) harness connector and ECM harness connector.
Measure Resistance of HO2S ground circuit between HO2S(down) harness connector and ECM harness connector.
Probe(+) : HO2S(up) harness connector NO1 and HO2S(down) harness connector NO1.
Probe(-) : ECM harness connector NO36 and ECM harness connector NO35.
Specification: below 1Ω
Does each resistance indicate continuity circuit?
YES
Go to "SHORT CIRCUIT INSPECTION FOR HO2S SIGNAL"
NO
Open circuit between HO2S harness connector and ECM harness connector
Repair as necessary and go to "Verification of Vehicle Repair" procedure
Turn ignition switch to OFF and disconnect HO2S(up) harness connector or HO2S(down) harness connector and ECM harness connector.
Measure resistance between HO2S(up) signal circuit and ground circuit.
Measure resistance between HO2S(down) signal circuit and ground circuit.
Probe(+) : HO2S(up) harness connector NO1 and HO2S(down) harness connector NO1.
Probe(-) : HO2S(up) harness connector NO2 and HO2S(down) harness connector NO2.
Specification: infinite
Does resistance indicate open circuit?
YES
Go to "SHORT CIRCUIT INSPECTION FOR HO2S TO BATTERY"
NO
Short circuit between HO2S signal circuit and ground circuit
Repair as necessary and go to "Verification of Vehicle Repair" procedure
Turn ignition switch to OFF and disconnect HO2S(up) harness connector or HO2S(down) harness connector and ECM harness connector.
Measure resistance between HO2S(up) signal circuit and chassis ground.
Measure resistance between HO2S(down) signal circuit and chassis ground.
Probe(+) : HO2S(up) harness connector NO2 and HO2S(down) harness connector NO2.
Probe(-) : Chassis ground.
Specification: infinite
Does resistance indicate open circuit?
YES
Go to "HO2S circuit short to battery inspection"
NO
Short circuit between HO2S signal circuit and chassis ground
Short to chassis ground between ECM harness connector and HO2S harness connector
Repair as necessary and go to "Verification of Vehicle Repair" procedure
