Circuit Description
The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 3 individual APP sensors within 1 housing. Three separate signal, low reference and 5-volt reference circuits connect the APP sensor assembly to the throttle actuator control (TAC) module. Each sensor has a unique functionality. The APP sensor 1 signal is pulled up to the reference voltage as the accelerator pedal is depressed, from below 1 volt at 0 percent pedal travel, with the pedal at rest, to above 2 volts at 100 percent pedal travel, with the pedal fully depressed. The APP sensor 2 signal is pulled down to the low reference from above 4 volts at 0 percent pedal travel to below 2.9 volts at 100 percent pedal travel. The APP sensor 3 signal is pulled down to low reference from above 3.8 volts at 0 percent pedal travel to below 3.1 volts at 100 percent pedal travel. Throttle position (TP) sensor 1 and APP sensor 1 share a 5 volt reference circuit that is connected within the TAC module. TP sensor 2 and APP sensor 2 share a 5-volt reference circuit that is connected within the TAC module. If only 1 APP sensor DTC is set, the redundant APP systems allow the TAC system to continue operating normally. One APP sensor DTC will not cause the Reduced Engine Power message to be displayed. Two APP sensor DTCs for the same sensor also will not cause the Reduced Engine Power message to be displayed.
This DTC incorporates 3 different diagnostic tests:
| • | APP sensor 1 signal circuit voltage out of range |
| • | Accelerator pedal minimum position for the APP sensor 1 out of range |
| • | 5-volt reference of the APP sensor 1 voltage out of range |
If the PCM detects one or more of the APP sensor 1 tests are out of range, DTC P2120 sets.
DTC Descriptor
This diagnostic procedure supports the following DTC:
DTC P2120 Accelerator Pedal Position (APP) Sensor 1 Circuit
Conditions for Running the DTC
| • | DTCs P0601, P0602, P0606, P2108 or U0107 are not set. |
| • | The ignition switch is in the crank or the run position. |
| • | The ignition voltage is greater than 5.23 volts. |
| • | DTC P2120 runs continuously once the above conditions are met. |
Conditions for Setting the DTC
| • | The PCM detects that the APP sensor signal voltage is less than 0.24 volts or more than 4.49 volts. |
| OR |
| • | The 5-volt reference voltage is less than 4.54 volts or more than 5.21 volts. |
| OR |
| • | The accelerator pedal minimum position for the APP sensor 1 is less than 0.24 volts. |
| • | One of the above conditions are present for more than 0.1 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 will not command Reduced Engine Power mode. |
| - | The control module will use the remaining two APP sensors to calculate throttle response. |
| • | If certain multiple APP sensor DTCs are set for more than one 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 message center displays Reduced Engine Power. |
| • | If all three APP sensors are out of range, the following occurs: |
| - | The control module commands Reduced Engine Power mode. |
| - | 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 TAC module connectors for signs of water intrusion. When water intrusion occurs, multiple DTCs could be set with no DTC circuit or component conditions found during diagnostic testing. |
| • | When the TAC module detects throttle movement with a DTC P2120 set, a DTC P2121 also sets. |
| • | When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the Capture Info. |
| • | For an intermittent, refer to Intermittent Conditions |
Test Description
The numbers below refer to the step numbers on the diagnostic table.
-
This test isolates whether the short is to another TAC system circuit in the harness or within the TAC module.
-
When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests that run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the Capture Info.
Step | Action | Values | Yes | No |
|---|---|---|---|---|
Schematic Reference: Engine Controls Schematics Connector End View References: Powertrain Control Module Connector End Views or Engine Controls Connector End Views | ||||
1 | Did you perform the Diagnostic System Check - Vehicle? | -- | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
2 |
Important: If DTC U0107 or P0120 is also set, refer to the appropriate DTC for further diagnosis.
Does the scan tool indicate APP sensor 1 voltage within the specified values? | 0.25-2.2 V | Go to Step 3 | Go to Step 6 |
3 | Depress the accelerator pedal to the wide open throttle (WOT) position. Does the scan tool indicate APP sensor 1 voltage within the specified values? | 2.24-4.2 V | Go to Step 4 | Go to Step 6 |
4 |
Did this DTC fail this ignition, during the above test ? | -- | Go to Step 24 | Go to Step 5 |
5 |
Did this DTC fail this ignition, during the above test ? | -- | Go to Step 19 | Go to Diagnostic Aids |
6 | Disconnect the APP sensor harness connector. Does the scan tool indicate APP sensor 1 voltage at the specified value? | 0 V | Go to Step 7 | Go to Step 11 |
7 | Connect a test lamp between the APP sensor 1 signal circuit and B+. Does the scan tool indicate APP sensor 1 voltage at the specified value? | 5 V | Go to Step 8 | Go to Step 13 |
8 | Test the APP sensor 1 5-volt reference circuit for voltage, with a DMM. Does the DMM indicate voltage within the specified values? | 4.6-5.4 V | Go to Step 10 | Go to Step 9 |
9 |
Does the DMM indicate voltage within the specified values? | 4.6-5.4 V | Go to Step 21 | Go to Step 16 |
10 |
Does the scan tool indicate the TP sensor 1 voltage is at the specified value? | 0 V | Go to Step 19 | Go to Step 17 |
11 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 12 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 22 | |
13 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 14 |
14 | Test the APP sensor 1 signal circuit for a short to ground, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 15 |
15 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 22 |
16 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 22 |
17 |
Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 18 |
18 | Test the TAC module ground circuit for an open or for high resistance, with a DMM. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 22 |
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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 20 |
20 | Replace the APP sensor assembly. Refer to Accelerator Pedal Position Sensor Replacement . Did you complete the repair? | -- | Go to Step 25 | -- |
21 | Did DTC P1120 set while performing step 9? | -- | Go to DTC P0120 | Go to Step 22 |
22 | 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 in Wiring Systems. Did you find and correct the condition? | -- | Go to Step 25 | Go to Step 23 |
23 | Replace the TAC module. Refer to Electronic Throttle Actuator Control Module Replacement . Did you complete the repair? | -- | Go to Step 25 | -- |
24 | Repair the intermittent condition as necessary. Refer to Connector Repairs and Wiring Repairs in Wiring Systems. Did you complete the repair? | -- | Go to Step 25 | -- |
25 |
Does the DTC run and pass? | -- | Go to Step 26 | Go to Step 2 |
Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? | -- | Go to Diagnostic Trouble Code (DTC) List - Vehicle in Vehicle DTC Information | System OK | |
