20/08/2021
𝐂𝐨𝐦𝐩𝐮𝐭𝐞𝐫 𝐈𝐧𝐩𝐮𝐭 𝐒𝐞𝐧𝐬𝐨𝐫𝐬.
𝐄𝐧𝐠𝐢𝐧𝐞 𝐓𝐡𝐫𝐨𝐭𝐭𝐥𝐞 𝐏𝐨𝐬𝐢𝐭𝐢𝐨𝐧 𝐒𝐞𝐧𝐬𝐨𝐫.
Late model engines with feedback carburetion or electronic fuel injection use a "Throttle Position Sensor" (TPS) to inform the computer about the rate of throttle opening and relative throttle position. A separate idle switch (sometimes called a "Nose" switch) and/or wide open throttle (WOT) switch may also be used to signal the computer when these throttle positions exist.
The throttle position sensor is usually mounted externally on the throttle shaft as is the case on most late model fuel injection throttle bodies.
The TPS sensor is essentially a variable resistor that changes resistance as the throttle opens. Think of it as the electronic equivalent of a mechanical accelerator pump. By signaling the computer when the throttle opens, the computer can richen up the fuel mixture to maintain the proper air/fuel ratio.
𝐓𝐏𝐒 𝐎𝐍 𝐃𝐑𝐈𝐕𝐄-𝐁𝐘-𝐖𝐈𝐑𝐄 𝐂𝐀𝐑𝐒.
Most late model cars and trucks have no throttle cable. A small electric motor is used to operate the throttle using inputs from position sensors on the gas pedal. When the gas pedal is depressed, the electrical resistance of the potentiometers inside the pedal sensors change. The control module notes the change in position and commands the throttle to open. A pair of throttle position sensors on the throttle shaft note the change in throttle position and provide feedback signals to the control module so the module knows the exact position of the throttle and that everything is working correctly.
𝐓𝐏𝐒 𝐒𝐄𝐍𝐒𝐎𝐑 𝐃𝐑𝐈𝐕𝐀𝐁𝐈𝐋𝐈𝐓𝐘 𝐒𝐘𝐌𝐏𝐓𝐎𝐌𝐒.
The classic symptom of a defective or misadjusted TPS is hesitation or stumble during acceleration (in other words, the same symptoms a bad accelerator pump would produce). The fuel mixture leans out because the computer doesn't receive the right signal telling it to add fuel as the throttle opens. The oxygen sensor feedback circuit will eventually provide the necessary information, but not quickly enough to prevent the engine from stumbling.
Throttle position sensors typically experience the most wear in the position just above idle, since this is the throttle's position for most driving. A worn sensor may cause a skip or drop in the reading when the throttle opens, causing a momentary loss of input to the PCM. The result is usually a hesitation or stumble because the PCM fails to provide the necessary fuel enrichment.
If the TPS mounting is loose, it will produce an erratic signal leading the ECM to believe the throttle is opening and closing. The result can be an unstable idle and intermittent hesitation.
If the TPS is shorted, the computer will receive the equivalent of a wide open throttle signal all the time. This will make the fuel mixture run rich and set a fault code that corresponds to a voltage signal that's too high.
If the TPS is open, the computer will think the throttle is closed all the time. The resulting fuel mixture will be too lean and a fault code that corresponds to a voltage signal that's too low will be set.
𝐓𝐏𝐒 𝐒𝐄𝐍𝐒𝐎𝐑 𝐂𝐇𝐄𝐂𝐊𝐒.
First, check for the presence of any fault codes. OBD II codes that may indicate TPS problems include:
P0120....Throttle/Pedal Position Sensor/Switch A Circuit
P0121....Throttle/Pedal Position Sensor/Switch A Circuit Range/Performance Problem
P0122....Throttle/Pedal Position Sensor/Switch A Circuit Low Input
P0123....Throttle/Pedal Position Sensor/Switch A Circuit High Input
P0124....Throttle/Pedal Position Sensor/Switch A Circuit Intermittent
P0220....Throttle/Pedal Position Sensor/Switch 'B' Circuit
P0221....Throttle/Pedal Position Sensor/Switch 'B' Circuit Range/Performance Problem
P0222....Throttle/Pedal Position Sensor/Switch 'B' Circuit Low Input
P0223....Throttle/Pedal Position Sensor/Switch 'B' Circuit High Input
P0224....Throttle/Pedal Position Sensor/Switch 'B' Circuit Intermittent
P0225....Throttle/Pedal Position Sensor/Switch 'C' Circuit
P0226....Throttle/Pedal Position Sensor/Switch 'C' Circuit Range/Performance Problem
P0227....Throttle/Pedal Position Sensor/Switch 'C' Circuit Low Input
P0228....Throttle/Pedal Position Sensor/Switch 'C' Circuit High Input
P0229....Throttle/Pedal Position Sensor/Switch 'C' Circuit Intermittent.
Abinibi Auto 2021.
