P0120
Throttle/Pedal Position Sensor/Switch "A" Circuit
- Severity
- High
- Driving
- Drive only to a garage
A fault in throttle or pedal position sensor "A". On a drive-by-wire car there is no cable between the pedal and the throttle - the module reads pedal position electronically and moves the throttle to match. Because the module cannot safely guess what the driver wants, a fault here usually triggers a reduced-power mode.
Possible causes
- CommonFailed throttle or pedal position sensor
- CommonDamaged wiring or connector at the sensor
- PossibleCarbon build-up on the throttle plate holding it off its stop
- PossibleCorroded connector letting water in
- RareControl module fault
What you might notice
- Sudden loss of power, or the engine refusing to rev beyond a low limit
- Warning light on, often with a separate throttle or power warning
- Erratic idle
- Poor or unpredictable throttle response
- Sometimes the engine will not start
What to check, in order
- Be careful where you drive with this fault. A reduced-power mode can engage without warning, which is dangerous when overtaking or joining fast-moving traffic.
- Inspect the connector at the sensor for corrosion, water and spread terminals.
- Watch the pedal and throttle position values on the live data screen while pressing the pedal slowly. Both should rise smoothly - a dropout or a flat spot identifies the fault.
- Check the wiring for chafing where the harness passes the engine or bulkhead.
- If the throttle plate is visibly carboned up, cleaning may help - but check whether your vehicle needs a throttle relearn procedure afterwards, because cleaning without it can leave the idle worse than before.
Read this code from your own car
Plug an ELM327 adapter into the OBD-II port under the dashboard. Pin16 reads every stored, pending and permanent code, explains each one like this page does — offline, with no account — and shows what the car recorded when the fault was set.
Where this code sits
P00xxP01xxP02xxP03xxP04xxP05xxP06xxP07xxP08xxP09xxP0AxxP0BxxP0CxxP0DxxP0ExxP0FxxP10xxP11xxP12xxP13xxP14xxP15xxP16xxP17xxP18xxP19xxP1AxxP1BxxP1CxxP1DxxP1ExxP1FxxP20xxP21xxP22xxP23xxP24xxP25xxP26xxP27xxP28xxP29xxP2AxxP2BxxP2CxxP2DxxP2ExxP2FxxP30xxP31xxP32xxP33xxP34xxP35xxP36xxP37xxP38xxP39xxP3AxxP3BxxP3CxxP3DxxP3ExxP3Fxx
Fuel and air metering
P0100P0101P0102P0103P0104P0105P0106P0107P0108P0109P0110P0111P0112P0113P0114P0115P0116P0117P0118P0119P0120P0121P0122P0123P0124P0125P0126P0127P0128P0129P0130P0131P0132P0133P0134P0135P0136P0137P0138P0139P0140P0141P0142P0143P0144P0145P0146P0147P0148P0149P0150P0151P0152P0153P0154P0155P0156P0157P0158P0159P0160P0161P0162P0163P0164P0165P0166P0167P0168P0169P0170P0171P0172P0173P0174P0175P0176P0177P0178P0179P0180P0181P0182P0183P0184P0185P0186P0187P0188P0189P0190P0191P0192P0193P0194P0195P0196P0197P0198P0199