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
Start engine and warm up to operating temperature.
Channel 1 Probe(+) : HO2S(up) harness connector NO2.
Channel 1 Probe(-) : Chassis ground.
Channel 2 Probe(+) : HO2S(down) harness connector NO2.
Channel 2 Probe(-) : Chassis ground.
Are the signal waveforms between front and rear HO2S same?
YES
Catalytic converter faulty
Repair as necessary and go to "Verification of Vehicle Repair"
NO
Temporarily install a known good ECM and check for proper operatiuon
If problem is corrected, replace ECM
