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
The voltage measurement of HO2S heater at ECM from heater input is for finding open or short circuit in harness.
Turn ignition switch to OFF and disconnect HO2S heater harness connector.
Turn ignition switch to ON
Measure voltage of HO2S heater battery voltage between HO2S harness connector and chassis ground.
Probe(+) : HO2S harness connector NO4.
Probe(-) : Chassis ground.
Specification: Approximately 12V
Is voltage within Specification?
YES
Go to "OPEN CIRCUIT INSPECTION FOR HO2S HEATER CONTROL"
NO
Open or short circuit to chassis ground between HO2S harness connector and control relay
Repair as necessary and go to "Verification of Vehicle Repair" procedure
In case,when checking sensor voltage,the output voltage is 0V.
▶Possible cause: Blown fuse or open circuit in harness between E/R-J/BOX and terminal 4 of HO2S heater.
Turn ignition switch to OFF and connect HO2S heater harness connector.
Turn ignition switch to ON
Measure voltage of HO2S heater battery voltage between ECM harness connector and chassis ground.
Probe(+) : ECM harness connector NO48 and NO28..
Probe(-) : Chassis ground.
Specification: Approximately 12V
Is voltage within Specification?
YES
Go to "SHORT CIRCUIT INSPECTION FOR HO2S HEATER SIGNAL"
NO
Open or short circuit to chassis ground 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 heater harness connector and ECM harness connector.
Turn ignition switch to ON
Measure resistance of HO2S heater signal circuit between HO2S harness connector and chassis ground.
Probe(+) : HO2S heater harness connector NO3.
Probe(-) : Chassis ground.
Specification: infinite
Is Resistance within Specification?
YES
Go to "SHORT CIRCUIT INSPECTION FOR HO2S HEATER POWER"
NO
Short circuit to chassis ground 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 ECM harness connector and HO2S(up,down) harness connector.
Measure voltage of HO2S heater signal circuit between HO2S harness connector and chassis ground.
Probe(+) : HO2S harness connector NO4.
Probe(-) : Chassis ground.
Specification: below 0.5V
Is voltage within Specification?
YES
Go to ""Component Inspection"
NO
Short to battery between HO2S harness connector and HO2S heater signal circuit
Repair as necessary and go to "Verification of Vehicle Repair" procedure
