P2121

DTC P2121

CIRCUIT DESCRIPTION
The accelerator pedal position (APP) sensor 1 and APP sensor 2 are potentiometer type sensors, each with the following circuits:
- A 5-Volt reference circuit
- A low reference circuit
- A signal circuit

The control module provides the APP sensors a 5-Volt reference circuit and a low reference circuit. The APP sensors then provide the control module signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is also low at rest and increases as the pedal is depressed.

This DTC incorporates the following diagnostic tests:
- The APP sensor 1 to APP sensor 2 correlation
- The accelerator pedal minimum position correlation between the APP sensor 1 and APP sensor 2
- The APP sensor 1 signal shorted to a 5-Volt reference, ground, or the APP sensor 2 signal

If the PCM detects one or more of the APP sensor 1 tests are out of range, DTC P2121 sets.

DTC DESCRIPTOR
This diagnostic procedure supports the following DTC:
DTC P2121 Accelerator Pedal Position (APP) Sensor 1 Performance

CONDITIONS FOR RUNNING THE DTC
- DTCs P0606, P2108, or U0107 are not set.
- The ignition switch is in the Crank or Run position.
- The ignition voltage is more than 5.23 volts.
- DTC P2121 runs continuously once the above conditions are met.

CONDITIONS FOR SETTING THE DTC
- The PCM detects that the APP sensor 1 disagrees with APP sensor 2 by more than 10.5 percent.
- The above condition is present for more than 0.14 second.

ACTION TAKEN WHEN THE DTC SETS
- The control module stores the DTC information into memory when the diagnostic runs and fails.
- The malfunction indicator lamp (MIL) will not illuminate.
- The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
- If one or more APP sensor DTCs are set for a single APP sensor, the following occurs:
- The control module commands Reduced Engine Power mode.
- The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.
- The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.
- The message center displays Reduced Engine Power.

CONDITIONS FOR CLEARING THE DTC
- A current DTC Last Test Failed clears when the diagnostic runs and passes.
- A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
- Clear the DTC with a scan tool.

DIAGNOSTIC AIDS
- Inspect the throttle actuator control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
- When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
- For an intermittent, refer to Testing for Intermittent Conditions and Poor Connections. Component Tests and General Diagnostics

TEST DESCRIPTION

Step 1 - Step 9:

Step 10 - Step 19:

The numbers below refer to the steps numbers in the diagnostic table.
2. This step determines if a communication condition exists.
5. This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 2 and sensor 3 is an accurate way of verifying the actual position of the pedal. The APP angles for all 3 sensors should be within a few percent of each other. If the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. If the pedal is fully depressed, all APP angles should be 100 percent.
6. The APP sensor 1 shares a common 5-Volt reference circuit with the throttle position (TP) sensor 1. Monitoring the TP sensor 1 voltage aids in diagnosing the APP sensor 5-Volt reference and low reference circuits.
9. With the TAC module still connected, this test will help determine a short to the signal circuit either within the TAC module or the wiring.
10. This step determines whether the TAC module or a shorted circuit is causing the condition.
19. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.