P0121 Throttle Position Sensor 1 Signal Circuit Range/Performance

COMPONENT LOCATION

GENERAL DESCRIPTION

The Electronic Throttle Control(ETC) system consists of the throttle body, Throttle Position Sensor(TPS)1&2 and Accelerator Position Sensor(APS) 1&2. TPS1&2 are sharing the same source voltage and ground. The ECM controls the throttle motor to open and close the throttle valve. The TPS1 output voltage increases smoothly in proportion with the throttle valve opening angle after starting. TPS2 output voltage decreases in inverse proportion with the throttle valve opening angle after starting. The TPS provides feedback to the ECM to control the throttle motor in order to control the throttle valve opening angle properly in response to the driver’s demands.

DTC DESCRIPTION

Checking output signals from TPS 1 and 2 under detecting condition, if output signals difference between TPS1 and TPS2 are detected more than 8% for the specified number of times., ECM sets P0121.

DTC DETECTING CONDITION

Item

Detecting Condition

Possible Cause

DTC Strategy

Determines if TPS#1 disagrees with TPS#2

1.	Poor Connection

2.	Open or short in TPS circuit

3.	Faulty TPS

4.	Faulty ECM

Enable Conditions

Ignition “ON”

Threshold value

Difference between average values of TPS1 and TPS2 > 8%

Diagnosis Time

Continuous

MIL On Condition

1 Driving Cycles

SPECIFICATION

Throttle Opening (°)	Output Voltage (V) [Vref=5.0]
Throttle Opening (°)	TPS1	TPS2
0°	0.0V	5.0V
10°	0.5V	4.5V
20°	0.9V	4.1V
30°	1.4V	3.6V
40°	1.8V	3.2V
50°	2.3V	2.7V
60°	2.7V	2.3V
70°	3.2V	1.8V
80°	3.6V	1.4V
90°	4.1V	0.9V
100°	4.5V	0.5V
110°	5.0V	0.0V

DIAGNOSTIC CIRCUIT DIAGRAM

SIGNAL WAVEFORM & DATA

Fig.1) Normal data & waveform of TPS1 & TPS2 with no accel pedal depressed under IG ON condition

Fig.2) Normal data & waveform of TPS1 & TPS2 with accel pedal depressed under IG ON condition

Fig.3) Abnormal data of TPS1 & TPS2 under open condition

MONITOR GDS DATA

1.	Connect GDS to Data Link Connector(DLC).

IG “ON”.

3.	Select “DTC” button, and then Press “DTC Status” to check DTC’s information from the DTCs menu.

4.	Read “DTC Status” parameter.

Is parameter displayed “Present fault”?

	▶ Go to “Terminal and Connector inspection” procedure.
	▶ Fault is intermittent caused by poor contact in the sensor’s and/or ECM’s connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary

TERMINAL AND CONNECTOR INSPECTION

1.	Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.

2.	Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage.

Has a problem been found?

	▶ Repair as necessary .
	▶ Go to ” Component Inspection ” procedure.

COMPONENT INSPECTION

■ Check TPS

IG “ON”

Monitor signal waveform of TPS by stepping on and off the accelerator pedal on GDS

Specification :

Throttle Opening (°)	Output Voltage (V) [Vref=5.0]
Throttle Opening (°)	TPS1	TPS2
0°	0.0V	5.0V
10°	0.5V	4.5V
20°	0.9V	4.1V
30°	1.4V	3.6V
40°	1.8V	3.2V
50°	2.3V	2.7V
60°	2.7V	2.3V
70°	3.2V	1.8V
80°	3.6V	1.4V
90°	4.1V	0.9V
100°	4.5V	0.5V
110°	5.0V	0.0V

Fig. 1) Normal waveform of TPS1 & TPS2 with no accel pedal depressed under IG ON condition

Fig. 2) Normal waveform of TPS1 & TPS2 with accel pedal depressed under IG ON condition

Is the measured signal waveform O.K ?

▶ Substitute with a known – good ECM and check for proper operation. If the problem is corrected, replace ECM .

There is a memory reset function on GDS that can erase optional parts automatically detected and memorized by ECM. Before or after testing ECM on the vehicle, use this function to reuse the ECM on the others

▶ Substitute with a known-good TPS and check for proper operation. If the problem is corrected, replace TPS and then. (After replacing ETC, do initialization of ETC as follows)

※ Procedure of ETS Initialization

Erase the trouble codes on ECM

Turn the ignition key off and keep this condition until the main relay is turned off.(It will take 10sec.)

Turn ignition key on more than 1second to record the throttle motor position on the EEPROM

New Videos on our YouTube Channel Every Week, Subscribe Now!

Related Posts