Alfa Romeo P0143 Heated Oxygen Sensor 3 Heater Control Circuit High

Description

OBD-II Trouble Code Description for P0143 Alfa Romeo

O2 Sensor Circuit Low Voltage

What does this mean?

OBD2 Code P0143 Alfa Romeo definition:
The Catalytic Converter is used to help control emissions. The PCM (Powertrain Control Module) uses the signal from the oxygen sensor to the rear of the catalyst to monitor the catalyst’s efficiency. This is the bank 1,3 sensor. It’s a four wire sensor being supplied a 0.5 volt reference voltage as well as a power and ground circuit for the o2 sensor heater element. There is also a signal wire from the oxygen sensor to the PCM that can vary between about 0.1 volts to about 0.9 volts according to oxygen content of the exhaust. A properly working post-cat sensor will exhibit small changes at a slower rate than front o2 sensors. To over simplify: a post-cat sensor’s main job is to monitor catalyst efficiency, not control fuel management (although they can have a measure of influence over the front o2 sensor’s operation). If the PCM determines that the post-cat o2 sensor signal voltage is below a certain threshold for too long, P0143 Alfa Romeo will set. PCM detected the HO2S signal was less than 156 mv for 28 seconds.

Symptoms

Possible sumptoms of OBD code P0143 Alfa Romeo
Usually rear o2 sensor problems won’t cause drivability issues since they are an input that measures catalyst efficiency (unlike front o2 sensors). However if you have other codes present, like lean codes or pre-o2 sensor codes, then they may cause drivability problems as well as P0143 Alfa Romeo. The following symptoms may be present: MIL (Malfunction Indicator Lamp) illumination Engine performance issues Engine running rough Engine running rich Poor idle

Causes

Possible causes of OBD code P0143 Alfa Romeo
An engine that is running lean could set this code, however there will likely be other codes present. Air leaks in exhaust in front of o2 sensor giving false reading O2 sensor connector damaged O2 sensor signal circuit is shorted to ground O2 sensor ground circuit is open O2 sensor has failed (it may be contaminated with fuel or coolant) PCM has failed

Possible Solutions

It’s always good to start with checking for air leaks in the exhaust manifold and in the exhaust pipes. With KOER (Key on engine running) use a scan tool or a voltmeter check the o2 sensor signal voltage with engine warm. You may have to increase the RPM to a fast idle to check the voltage of the bank 1,3 sensor. If it’s voltage is stuck low (less than a half a volt) and you don’t have any other o2 sensor codes present in the PCM, then it’s a good bet that the sensor is bad. If the voltage isn’t stuck low and the o2 sensor seems to be operating fine, it’s likely sticking low intermittently. This often turns out to be the sensor. Having said that, if you’re interested in knowing for sure what the problem is then perform the following: 1. Turn off the engine and unplug the 1,3 o2 sensor connector. Make sure that there is battery voltage present and ground present for the o2 sensor heater. If there isn’t then diagnose that first then retest. If that checks out then, using a jumper wire, supply a chassis ground to the o2 sensor connector(PCM side) ground circuit. Now observe the scan tool bank 1,3 o2 sensor reading. If it is now at about a half a volt then replace the o2 sensor. If, after supplying a ground to the unplugged PCM side of the o2 sensor connector, the voltage reading doesn’t change then check the harness for short to ground. Check for harness making contact with exhaust components. Check pins for damage, and for moisture. Repair as necessary. If you can find no harness problems, then the PCM may be bad.

The OBD2 Code Information Be Applicable For Alfa Romeo:

2014 Alfa Romeo MiTo new,,2014 Alfa Romeo Giulietta new,,2014 Alfa Romeo 4C,,2013 Alfa Romeo Gloria Concept,,2013 Alfa Romeo Disco Volante Touring,,2012 Alfa Romeo Disco Volante Touring Concept,,2011 Alfa Romeo TZ3 Stradale,,2011 Alfa Romeo Giulietta,,2011 Alfa Romeo 4C Concept,,2010 Alfa Romeo TZ3 Corsa,,2010 Alfa Romeo Pandion Concept,,2010 Alfa Romeo MiTo Quadrifoglio Verde,,2010 Alfa Romeo MiTo 1.4 MultiAir,,2010 Alfa Romeo 2uettottanta Concept,,2010 Alfa Romeo 159 1750 TBi,,2009 Alfa Romeo MiTo UK Version,,2009 Alfa Romeo MiTo GTA Concept,,2009 Alfa Romeo Mi.To,,2009 Alfa Romeo Brera S,,2009 Alfa Romeo 8C Spider,,2009 Alfa Romeo 159 Sportwagon,,2009 Alfa Romeo 159,,2007 Alfa Romeo GT Q2,,2007 Alfa Romeo 8c Competizione,,2007 Alfa Romeo 147 Q2,,2007 Alfa Romeo 147 Murphy and Nye,,2007 Alfa Romeo 147 CnC,,2006 Alfa Romeo Spider UK Version,,2006 Alfa Romeo Spider,,2006 Alfa Romeo 159 Sportwagon,,2005 Alfa Romeo Brera UK Version,,2005 Alfa Romeo Brera,,2005 Alfa Romeo 159,,2004 Alfa Romeo Visconti Concept ItalDesign,,2004 Alfa Romeo 8C Competizione,,2004 Alfa Romeo 166,,2004 Alfa Romeo 156 GTA Autodelta,,2004 Alfa Romeo 156 Crosswagon Q4,,2004 Alfa Romeo 156 Crosswagon,,2004 Alfa Romeo 147 5door,,2004 Alfa Romeo 147 3door,,2003 Alfa Romeo Spider,,2003 Alfa Romeo Kamal Concept,,2003 Alfa Romeo GTV,,2003 Alfa Romeo GT,,2003 Alfa Romeo 156 Sportwagon 2.0 JTD,,2003 Alfa Romeo 156 GTA Autodelta,,2003 Alfa Romeo 156 2.4 JTD,,2003 Alfa Romeo 147 TI,,2002 Alfa Romeo 147 JTD 16V,,2002 Alfa Romeo 147 GTA

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