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SNAPONTECH
SNAPONTECH, Technician
Category: Car
Satisfied Customers: 3803
Experience:  2 year Associate in Applied Arts and Sciences Degree in Automotive Repair Technology
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metro: geo..blew..exhaust down and unable to remove o2 sensor..haynes

Resolved Question:

1997 geo metro down stream o2 sensor wire rubbed and blew fuse. took exhaust down and unable to remove o2 sensor. i want to check sensor to see if ok, however, haynes book for this vehicle does not provide troubleshooting info. need voltages & color code. HELP!
Submitted: 5 years ago.
Category: Car
Expert:  SNAPONTECH replied 5 years ago.

SNAPONTECH :

Welcome to Justanswer

SNAPONTECH :

Get the car completely warmed up Then You are looking for voltage to go above and below 0.45 volts. If you see less than 0.2 and more than 0.7 volts and the value changes rapidly, you are through, your sensor is good. If not, is it steady high (> 0.45) near 0.45 or steady low (< 0.45). If the voltage is near the middle, you may not be hot yet. Run the engine above 2000 rpm again. If the reading is steady low, add richness by partially closing the choke or adding some propane through the air intake. Be very careful if you work with any extra gasoline, you can easily be burned or have an explosion. If the voltage now rises above 0.7 to 0.9, and you can change it at will by changing the extra fuel, the O2 sensor is usually good. If the voltage is steady high, create a vacuum leak. Try pulling the PCV valve out of it's hose and letting air enter. You can also use the power brake vacuum supply hose. If this drives the voltage to 0.2 to 0.3 or less and you can control it at will by opening and closing the vacuum leak, the sensor is usually good. If you are not able to make a change either way, stop the engine, unhook the sensor wire from the computer harness, and reattach your voltmeter to the sensor output wire. Repeat the rich and lean steps. If you can't get the sensor voltage to change, and you have a good sensor and ground connection, try heating it once more. Repeat the rich and lean steps. If still no voltage or fixed voltage, you have a bad sensor. If you are not getting a voltage and the car has been running rich lately, the sensor may be carbon fouled. It is sometimes possible to clean a sensor in the car. Do this by unplugging the sensor harness, warming up the engine, and creating a lean condition at about 2000 rpm for 1 or 2 minutes. Create a big enough vacuum leak so that the engine begins to slow down. The extra heat will clean it off if possible. If not, it was dead anyway, no loss. In either case, fix the cause of the rich mixture and retest. If you don't, the new sensor will fail.

SNAPONTECH :

This can be done using a scan tool instead of trying to get near the exhaust and attempting to test

SNAPONTECH :

If the O2 sensor is out of reading it will set a code because it will be out of range for the voltage

Customer:

thank you. i need color code for wires so i can back probe

SNAPONTECH :

do you have 2 or 4

Customer:

thanks but need to know color code of wires

SNAPONTECH :

which engine do you have?

Customer:

4

Customer:

4 cylinder

SNAPONTECH :

There are two different options which wire colors do you have

Customer:

one moment pls

SNAPONTECH :

yep

Customer:

2 black 1 white 1blue

SNAPONTECH :

Ok the 2 black go to the heater

SNAPONTECH :

These you will not need to test

Customer:

where the connector snaps in call that the top. white & blue side by side with black wire under each

SNAPONTECH :

You will put the probe on the blue power signal wire white

Customer:

ok got it

SNAPONTECH :

you should measure in mili volts 900 is rich and 100 is lean

SNAPONTECH :

Just monitor and see if it works properly

SNAPONTECH :

Let me know if you need anything else. If this was helpful please kindly press ACCEPT. Thanks Danny

Customer:

i need to write down your instructions and will then press accept. thanks -john

SNAPONTECH :

No problem Have a great day follow up is free if you need anything else

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