P2121
3MZ-FE ENGINE CONTROL SYSTEM: SFI SYSTEM: P2121: Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance
DTC P2121 - Throttle / Pedal Position Sensor / Switch "D" Circuit Range / Performance
CAUTION / NOTICE / HINT
HINT: This DTC relates to the Accelerator Pedal Position (APP) sensor.
DESCRIPTION
HINT:
- This Electronic Throttle Control System (ETCS) does not use a throttle cable.
- This accelerator pedal position sensor is a non-contact type.
The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal position sensor has 2 sensor elements / signal outputs: VPA1 and VPA2. VPA1 is used to detect the actual accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA1. Voltage applied to VPA1 and VPA2 changes between 0 V and 5 V in proportion to the accelerator pedal angle.
The ECM monitors the accelerator pedal angle from VPA1 and VPA2 signal outputs, and controls the throttle motor based on these signals.
HINT: After confirming DTCs P2120, P2122, P2123, P2125, P2127, P2128 and P2138, use Techstream or the OBD II scan tool to confirm the accelerator pedal position sensor output voltage.
MONITOR DESCRIPTION
The accelerator pedal position sensor is mounted on the accelerator pedal bracket. The accelerator pedal position sensor has 2 sensor elements and 2 signal outputs: VPA and VPA2. VPA is used to detect the actual accelerator pedal angle (used for engine control) and VPA2 is used to detect malfunctions in VPA. When the difference between the voltage outputs of VPA and VPA2 deviates from the standard, the ECM determines that the accelerator pedal position sensor is malfunctioning. The ECM turns on the MIL and the DTC is set.
MONITOR STRATEGY
TYPICAL ENABLING CONDITIONS
TYPICAL MALFUNCTION THRESHOLDS
FAIL-SAFE
The accelerator pedal position sensor has 2 (main and sub) sensor circuits. If a malfunction occurs in either of the sensor circuits, the ECM detects the abnormal signal voltage difference between the 2 sensor circuits and switches to limp mode. In limp mode, the functioning circuit is used to calculate the accelerator pedal opening angle to allow the vehicle to continue driving. If both circuits malfunction, the ECM regards the opening angle of the accelerator pedal as being fully closed. In this case, the throttle valve remains closed as if the engine is idling.
If a pass condition is detected and then the ignition switch is turned off, the fail-safe operation stops and the system returns to a normal condition.
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT: Read freeze frame data using Techstream. The ECM records vehicle and driving condition information as freeze frame data the moment a DTC is stored. When troubleshooting, freeze frame data can be helpful in determining whether the vehicle was running or stopped, whether the engine was warmed up or not, whether the air-fuel ratio was lean or rich, as well as other data recorded at the time of a malfunction.
PROCEDURE
1. READ VALUE OF TECHSTREAM (ACCEL POS #1 AND ACCEL POS #2)
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch to the ON position and turn the tester on.
(c) Select the following menu items: Powertrain / Engine and ECT / Data List / ETCS / Accelerator Position No. 1 and Accelerator Position No. 2.
(d) Read the values displayed on the tester.
Standard voltage:
OK -- CHECK WHETHER DTC OUTPUT RECURS (ACCELERATOR PEDAL POSITION SENSOR DTCS)
NG -- Continue to next step.
2. CHECK HARNESS AND CONNECTOR (ACCELERATOR PEDAL POSITION SENSOR - ECM)
(a) Disconnect the Accelerator Pedal Position (APP) sensor connector.
(b) Disconnect the ECM connector.
(c) Measure the resistance.
Standard resistance:
Check for open
Check for short
(d) Reconnect the APP sensor connector.
(e) Reconnect the ECM connector.
NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
3. REPLACE ACCELERATOR PEDAL
(a) Replace the accelerator pedal (Components).
NEXT -- Continue to next step.
4. CHECK WHETHER DTC OUTPUT RECURS (ACCELERATOR PEDAL POSITION SENSOR DTCS)
(a) Connect Techstream to the DLC3.
(b) Turn the ignition switch to the ON position and turn the tester on.
(c) Clear the DTCs (DTC Check / Clear).
(d) Start the engine.
(e) Allow the engine to idle for 15 seconds.
(f) Select the following menu items on the tester: Powertrain / Engine and ECT / Trouble Codes.
(g) Read the DTCs.
Result:
B -- SYSTEM IS OK
A -- REPLACE ECM