jeep liberty 2004 3.7 trouble codes 0172 and 0171 at the same time
- overdrive138
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please help thx
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- Andy.MacFadyen
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Then look at live data particularly short and long term fuel trims and O2 sensor output voltage at idle and about 3,000 rpm.
Also are there any splits or leaks anywhere in the air intake ? ---- anything non-standard about the airfilter
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- overdrive138
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- overdrive138
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0137(low voltage) shorted to ground?
0171(lean) shorted to ground?
0172(rich) shorted to voltage?
You should check o2 sensor wires and voltage reference from PCM signal line.
I wouldn't discard 0137 as fixed.
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- overdrive138
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- kostelectronics
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- juergen.scholl
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freeze frame and live data will b of help.
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- overdrive138
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- cheryl hartkorn
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- juergen.scholl
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overdrive138 wrote: when u say compare pre and postcat o2 what exactly am i comparing? thx
You compare the voltage readings of the 2 sensors, the one before the catalytic converter and the one behind it....(of the same bank, obiously).
The front one should show an oscillating or fluctuating signal somewhere between 100 mV and 900 mV . This would indicate that the computer has got fuel control and is able to alter the mixture in order to feed the converter with the proper air/fuel mixture to make it work.
The second sensor, the one behind the catalytic converter, should show a much more stable voltage reading if the converter itself is working properly. This voltage may read around 300mV or 700mV, depending on design and system. With your new verus you can compare the sensors' voltages easily in graphic mode.
If the second sensor shows fluctuating voltages similar to the pre cat sensor - in other words the second sensor is mirroring the first one - then the converter is not doing its job, hth.
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- Matts Auto
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Easy test is to remove supply vapor line to the Purge control solenoid which is usually mounted right near or intake or driver side fender, easy test is turn the key on, turn on the smoke generator and if any smoke comes out of the solenoid out of the unplugged port to fuel tank there is your problem.
Almost any scanner will allow you the test ability to perform a purge control solenoid test and it allows you to cycle it in 10% increments and should allow you to see the duty cycle while performing this test. The Purge control solenoid should be completely closed at idle and with KOEO. same test can be performed on just about any chrysler or dodge vehicles. Again very easy to find it, your computer may also show Large evap system leak.
Hope that helps
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