Diagnostic Instructions
| • | Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure. |
| • | Review Strategy Based Diagnosis for an overview of the diagnostic approach. |
| • | Diagnostic Procedure Instructions provides an overview of each diagnostic category. |
DTC Descriptors
DTC P2127: Accelerator Pedal Position (APP) Sensor 2 Circuit Low VoltageDTC P2128: Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage
Diagnostic Fault Information
Circuit | Short to Ground | Open | Short to Voltage | Signal Performance |
|---|---|---|---|---|
APP Sensor 2 Signal | P2127 | P2128 | P2128 | P2138 |
APP Sensor 2 5-Volt Reference | P2127 | P2127 | P2128 | -- |
APP Sensor 2 Low Reference | -- | P2128 | -- | -- |
Typical Scan Tool Data
Circuit | Short to Ground | Open | Short to Voltage |
|---|---|---|---|
Parameter Normal Range: 0.13-4.87 V | |||
APP Sensor 2 Signal | 0 V | 0 V | 5 V |
APP Sensor 2 5-Volt Reference | 0 V | 0 V | 5 V |
APP Sensor 2 Low Reference | -- | 5 V | -- |
Circuit/System Description
The throttle actuator control (TAC) system uses two accelerator pedal position (APP) sensors to monitor the accelerator pedal position. The APP sensors 1 and 2 are located within the pedal assembly. Each sensor has the following circuits:
| • | A 5-volt reference circuit |
| • | A low reference circuit |
| • | A signal circuit |
Two processors are also used to monitor the TAC system data. Both processors are located within the engine control module (ECM). Each signal circuit provides both processors with a signal voltage proportional to pedal movement. Both processors monitor each other's data to verify that the indicated APP calculation is correct.
Conditions for Running the DTC
| • | The system voltage is more than 7 volts. |
| • | The ignition is in the Unlock/Accessory or Run position. |
| • | DTC P2127 and P2128 run continuously when the above conditions are met. |
Conditions for Setting the DTC
P2127
The ECM detects that the APP sensor 2 voltage is less than 0.66 volt for more than 0.4 second.
P2128
The ECM detects that the APP sensor 2 voltage is more than 4.82 volts for more than 0.4 second.
Action Taken When the DTC Sets
| • | DTCs P2127 and P2128 are Type A DTCs. |
| • | The control module commands the TAC system to operate in the Reduced Engine Power mode. |
| • | A message center or an indicator displays Reduced Engine Power. |
Conditions for Clearing the MIL/DTC
DTCs P2127 and P2128 are Type A DTCs.
Reference Information
Schematic Reference
Connector End View Reference
Description and Operation
Throttle Actuator Control (TAC) System Description
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
- Ignition ON, observe the scan tool APP sensor 2 voltage parameter. The reading should be between 0.66-4.82 volts and change with accelerator pedal input.
- Ignition ON, observe the scan tool APP Sensor 1 and 2 parameter. The scan tool should indicate agree.
- Clear the DTCs with the scan tool. Operate the vehicle within the Conditions for Running the DTC, or within the conditions that you observed from the Freeze Frame/Failure Records.
- Verify that DTCs P0698 or P0699 are not set.
| ⇒ | If DTCs P0641, P0642, P0643, P0651, P0652, P0653, P0697, P0698 or P0699 is set, refer to DTC P0641-P0643, P0651-P0653, or P0697-P0699 . |
Circuit/System Testing
- Ignition OFF, disconnect the accelerator pedal harness connector at the accelerator pedal. Allow sufficient time for the ECM to power down.
- Test for less than 3 ohms of resistance between the low reference circuit terminal A and ground.
- Ignition ON, test for 4.8-5.2 volts between 5-volt reference circuit terminal C and ground.
- Ignition ON, verify the scan tool APP sensor 2 voltage is less than 0.1 volt.
- Install a 3A fused jumper wire between the signal circuit terminal B and the 5-volt reference circuit terminal C of the APP sensor 2, and verify that the APP sensor 2 voltage is greater than 4.8 volts.
- If all circuits test normal, replace the accelerator pedal.
| ⇒ | If greater than 3 ohms, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than 4.8 volts, test the 5-volt reference circuit for an open/high resistance or short to ground. If the circuit tests normal, replace the control module. |
| ⇒ | If greater than 5.2 volts, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the control module. |
| ⇒ | If greater than 0.1 volt, test the APP sensor 2 signal circuit terminal B for a short to voltage. If the circuit tests normal, replace the ECM. |
| ⇒ | If less than 4.8 volts, test the APP sensor 2 signal circuit for an open/high resistance, or short to ground. If the circuit tests normal, replace the control module. |
Component Testing
Important: Circuit/System Testing must be performed before proceeding with Component Testing.
Dynamic Test
- Install a 3A fused jumper wire between the 5-volt reference terminal of the applicable APP sensor and 5 volts. Install a jumper wire between the low reference terminal and a ground.
- Sweep the sensor through the entire range while monitoring the voltage between the signal terminal and the low reference terminal with a DMM. the voltage should vary between 0.66-4.82 volts with out any spikes or dropouts.
| ⇒ | If the voltage is not within the specified range or is erratic, replace the accelerator pedal assembly. |
Repair Instructions
Perform the Diagnostic Repair Verification after completing the diagnostic procedure.
