Description
OBD-II Trouble Code Description for P0120 Alfa Romeo
Throttle/Pedal Position Sensor/Switch “A” Circuit
What does this mean?
OBD2 Code P0120 Alfa Romeo definition:
The TPS (Throttle Position Sensor) is a potentiometer that is mounted to the throttle body. It detects the throttle blade angle. As the throttle blade moves, the TPS sends a signal to the PCM (Powertrain Control Module). Usually a three wire sensor: A 5 volt reference from the PCM to the TPS, a ground from the PCM to the TPS, and a signal return from the TPS to the PCM.
The TPS sends the throttle position information back to the PCM on this signal wire. When the throttle is closed the signal is near .45 volts. At WOT (Wide Open Throttle) the TPS signal voltage will approach a full 5 volts. When the PCM sees a voltage that is outside of normal operating range, P0120 Alfa Romeo will set.
NOTE: The PCM knows that any large change in throttle position means a cooresponding change in manifold pressure (MAP). On some models the PCM will monitor MAP and TPS operation for comparison. Meaning that if the PCM sees a large percentage change in throttle position, it expects to see a cooresponding change in manifold pressure and vice versa. If it doesn’t see this comparitive change, P0120 Alfa Romeo may set. This doesn’t apply to all models.
Symptoms
Possible sumptoms of OBD code P0120 Alfa Romeo
Potential symptoms include:
MIL (Malfunction Indicator Lamp) illumination
Misfiring at idle or at highway speed
Poor idle quality
Possibly won’t idle
Possibly starts and stalls
Causes
Possible causes of OBD code P0120 Alfa Romeo
Potential causes of the P0120 Alfa Romeo code include:
Sticking throttle return spring
MAP or TPS connector corrosion
Misrouted harness causing chafing
Bad TPS
Bad PCM
Possible Solutions
If you have access to a scan tool, with KOEO (Key on engine off) observe the TPS voltage. With throttle closed, voltage should be about .45 volts. It should gradually sweep upwards to approximately 4.5 to 5 volts as you depress the throttle. Sometimes only a scope can capture an intermittent glitch in the TPS signal voltage. If you notice a glitch in the TPS sweep voltage, replace the TPS.
NOTE: Some TPS sensors require fine adjustment. If you aren’t comfortable with using a DVOM (Digital Volt Ohm meter) to adjust the new TPS, then it’s best to take the vehicle to a shop. If the voltage is not .45 volts (+or- .3 volts or so) with the throttle closed or if the reading is “stuck” then unplug the TPS connector. With KOEO check for 5 volts reference voltage present at the connector and a good ground. You can check the signal circuit for continuity by jumping a fused wire between the ground circuit of the TPS connector and the signal circuit. If the TPS reading on the scan tool now reads zero, then replace the TPS. However if that doesn’t change the reading to zero, then check for an open or a short on the signal wire and if none is found, suspect a bad PCM. If manipulating the TPS wiring harness causes any change in idle, then suspect bad TPS.
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
Note:
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