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Ron
Ron, ASE Certified Technician
Category: Toyota
Satisfied Customers: 33478
Experience:  ASE Certified Tech
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02 sensor JA: Thanks. Can you give me any more details about

Customer Question

02 sensor
JA: Thanks. Can you give me any more details about your issue?
Customer: 98 four runner 3.4 cel been on replaced both sensors still cel is on, checked ecm connector 11.. Pin # ***** & 11 back probe this cone tot only to have 3 volts if I pull the connector and probe it it has 12 volts these are wires white with blue tracer and red with white tracer
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Submitted: 7 months ago.
Category: Toyota
Expert:  Ron replied 7 months ago.
Hello, my name is ***** ***** I am a professional here at Just Answer. I have noticed that your question was not getting a response and thought I would see if you still need help with this.I apologize for the delay and I hope I can still assist you with this here.If you can give me the actual fault code and or codes your getting on your Four Runner I will see if I can help you with them with the proper testing. Post back when you can and we can work from there.
Customer: replied 7 months ago.
Po135 po141 check engine lite on,replaced both of af sensors after cel came on.still have codes after pulling efi fuse.sensors are working after engine warm up.but I do not see voltage at cold start
Customer: replied 7 months ago.
Back probed ecm connector 11 wires r/w and w/blue tracer they sit side by side in connector reading 2.75 volts each when plugged in to ecm. But if I pull connector and probe it it shows 12 volts at each pin
Customer: replied 7 months ago.
Engine runs good maybe a little lean coolant temp sensors working good, replaced fuel filter. Checked efi relay.cant find a vac leak, cleaned pcv valve
Customer: replied 7 months ago.
Seems odd to be ecm but maybe
Customer: replied 7 months ago.
Have been using live data scanner to see so sensor signals,
Expert:  Ron replied 7 months ago.
Try using the factory pinpoint test steps in the link below, copy and paste the link to your browser to open and view them.https://dl.dropboxusercontent.com/u/104923897/HO2S%20testing%20Apr17.pdf
Customer: replied 7 months ago.
Don't have 12 volts at ecm only 3volts but if I remove connector and probe there is 12 volts, funny. So trouble chart says my ecm Ok but bad circuit between efi.and o2 sensors have you ever diag a ecm before with these codes
Customer: replied 7 months ago.
My question. Ron 12 volts is going to ecm but when I test with connector plugged in its not giving me 12volts as soon as I pull connector 11 and probe the ht1 and ht2 pins on connector then only I get 12 is ecm rejecting these 12 volts. Seem like efi power source is good. But ecm does not accept this. Your Toyota flow chart says check wiring harness. A little advise would be nice. As to Toyota flow chart I have this already chiton online
Expert:  Ron replied 7 months ago.
It dose sound like the problem is with the ECM. All you need to do to check the wiring harness is ohm check the wires from the HO2S sensor to the PCM to make sure there are no open and or shorts to ground.

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