P0121 - Throttle Position Sensor/Switch A Circuit Range/Performance Problem
POST UPDATED IN January, 2023
Description of DTC code P0121 Generic
The TPS is a potentiometer used to indicate how much acceleration the driver needs. This has a 5-volt reference power and emits a ground signal, which comes from the PCM (Powertrain Control Module).
The sensor is used by the PCM to control both the delivery of fuel, and to operate the automatic transmission. A general measure is: At rest: 0.5 volts; and at full speed: 4.5 volts. If the PCM verify the angle of this accelerator is less or greater than that needed for a specific RPM (Revolutions Per Minute), the DTC code P0121 is established.
There may be irregularities in the acceleration / deceleration.
When accelerating, black smoke comes out of the exhaust pipe.
The vehicle may not start.
Causes of OBD2 P0121 Generic
A code P0121 can be caused by the following problems:
There are open lines in the sensor connection to the PCM.
There are readings that are out of range.
The TPS sensor may be damaged.
The PCM could have failures.
The acceleration system may be failing.
Possible solutions of the DTC code P0121 Generic
With a scan tool, check the readings that give the idle and Wide-Open Throttle, to the TPS (Throttle Position Sensor) and check if they are within the specifications mentioned. If that is not the case, replace the TPS and verify again.
With an oscilloscope There must be no short circuit in the TPS signal, there should be no abandonment.
Move the TPS connector and the harness, at the same time, see the pattern and if it is abandoned you could substitute the TPS and recheck.
Check that there is 5 volts of reference in the TPS connector, if so, verify the circuit to ground.
There may be a short circuit, to check it make sure that the signal circuit is not 12 volts.
Verify that the connector has no water, if so, you could replace it.