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. |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View Reference: Engine Controls Connector End Views or Powertrain Control Module Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | |
2 |
Important: If DTCs P0220 or U0107 are also set, refer to Diagnostic Trouble Code (DTC) List - Vehicle and diagnose the applicable DTC first.
Does the scan tool indicate the APP sensor 2 voltage is more than the specified value? | 0.24 V | Go to Step 3 | Go to Step 6 |
3 | Fully depress the accelerator pedal to the wide open throttle (WOT) position. Does the scan tool indicate the APP sensor 2 voltage is less than the specified value? | 4.49 V | Go to Step 4 | Go to Step 6 |
4 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 5 |
5 | Slowly depress the accelerator pedal to WOT, then slowly return the pedal to closed throttle while observing the DTC status. Did the scan tool indicate this DTC failed this ignition during the above test? | -- | Go to Step 17 | Go to Diagnostic Aids |
6 |
Does the DMM indicate the APP sensor 2 signal voltage is at the specified value? | 0 V | Go to Step 7 | Go to Step 8 |
7 | Connect a test lamp between the APP Sensor 2 Signal circuit and B+. Does the scan tool indicate the APP Sensor 2 Voltage parameter is at the specified value? | 5 V | Go to Step 12 | Go to Step 9 |
8 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 11 |
9 | Test the APP sensor 2 signal circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 10 |
10 | Test the APP sensor 2 signal circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs. | -- | Go to Step 23 | Go to Step 11 |
11 | Test for a short between the APP sensor 2 signal circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
12 | Test the APP sensor 2 5-volt reference circuit for voltage with a DMM. Does the DMM indicate voltage within the specified values? | 4.8-5.2 V | Go to Step 17 | Go to Step 13 |
13 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 14 |
14 | Test the APP sensor 2 5-volt reference circuit for an open or high resistance with a DMM. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 15 |
15 | Test the APP sensor 2 5-volt reference circuit for a short to ground with a DMM. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 16 |
16 | Test for a short between the APP sensor 2 5-volt reference circuit and all other TAC module circuits with a DMM. Refer to Circuit Testing and Wiring Repairs. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
17 | Measure resistance with a DMM connected between the APP sensor 2 low reference circuit and the APP sensor 1 low reference circuit. Does the DMM indicate resistance within the specified values? | 0-5 Ω | Go to Step 19 | Go to Step 18 |
18 |
Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 21 |
19 | Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 20 |
20 | Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement. Did you complete the replacement? | -- | Go to Step 23 | -- |
21 | Inspect for poor connections at the harness connector of the TAC module. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals. Did you find and correct the condition? | -- | Go to Step 23 | Go to Step 22 |
22 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement. Did you complete the replacement? | -- | Go to Step 23 | -- |
23 |
Did the DTC fail this ignition? | -- | Go to Step 2 | Go to Step 24 |
Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | System OK | ||
