Buick Regal: DTC P2122, P2123, P2127, P2128, or P2138
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 provide an overview of each diagnostic
category.
DTC Descriptors
DTC P2122
Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage
DTC P2123
Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage
DTC P2127
Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage
DTC P2128
Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage
DTC P2138
Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible
Diagnostic Fault Information
Typical Scan Tool Data
APP Sensor 1
APP Sensor 2
Circuit/System Description
The accelerator pedal assembly contains 2 accelerator pedal position (APP)
sensors. The APP sensors
are mounted to the accelerator pedal assembly and are not serviceable. The APP
sensors provide a signal
voltage that changes relative to pedal position. The engine control module (ECM)
supplies each APP
sensor with a 5 V reference circuit, a low reference circuit, and a signal
circuit.
Conditions for Running the DTC
P2122, P2123, P2127, P2128
- DTC P0697 and P06A3 are not set.
- The ignition is ON or the engine is running.
- The run/crank or powertrain relay voltage is greater than 6.0 V and
reduced power is not active.
- DTC P2122, P2123, P2127, P2128 run continuously when the above
conditions are met.
P2138
- DTC P0697, P06A3, P2122, P2123, P2127, and P2128 are not set.
- The ignition is ON or the engine is running.
- The run/crank or powertrain relay voltage is greater than 6.0 V and
reduced power is not active.
- DTC P2138 runs continuously when the above conditions are met.
Conditions for Setting the DTC
P2122
The ECM detects the APP sensor 1 voltage is less than 0.46 V for greater than
1 s.
P2123
The ECM detects the APP sensor 1 voltage is greater than 4.75 V for greater
than 1 s.
P2127
The ECM detects the APP sensor 2 voltage is less than 0.32 V for greater than
1 s.
P2128
The ECM detects the APP sensor 2 voltage is greater than 2.6 V for greater
than 1 s.
P2138
The ECM detects the voltage difference between APP sensor 1 and APP sensor 2
exceeds a
predetermined value for greater than 1 s.
Action Taken When the DTC Sets
- DTCs P2122, P2123, P2127, P2128, and P2138 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.
- Under certain conditions the control module commands the engine OFF.
Conditions for Clearing the MIL/DTC
DTCs P2122, P2123, P2127, P2128, and P2138 are Type A DTCs.
Diagnostic Aids
A high resistance condition on the accelerator pedal sensor circuits could
cause a DTC to set.
Ensure that the in-line harness connector seals are installed correctly.
Improper installation could result
in water intrusion into the connector and cause a DTC to set.
Reference Information
Schematic Reference
Engine Controls Wiring Schematics (LTG)
Connector End View Reference
Component Connector End View Index
Description and Operation
Throttle Actuator Control (TAC) System Description
Electrical Information Reference
- Circuit Testing
- Connector Repairs
- Testing for Intermittent Conditions and Poor Connections
- Wiring Repairs
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References for scan tool information
Circuit/System Verification
1. Ignition ON.
2. Verify DTC P0697 or P06A3 is not set.
- If any of the DTCs are set
Refer to DTC P0641, P0651, P0697, P06A3, or P06D2 for further diagnosis.
- Go to next step: If none of the DTCs are set
3. Verify the scan tool APP Sensor 1 Circuit Status and APP Sensor 2 Circuit
Status parameters
display OK.
Refer to Circuit/System Testing.
- Go to next step: If OK is displayed
4. Verify the scan tool APP Sensor 1 and 2 parameter displays Agree while
performing the tests
listed below:
- Rapidly depress the accelerator pedal from the rest position to the wide
open throttle
position (WOT) and release pedal. Repeat the procedure several times.
- Slowly depress the accelerator pedal to WOT and then slowly return the
pedal to closed
throttle. Repeat the procedure several times.
- If Disagree
Refer to Circuit/System Testing
- Go to next step: If Agree
5. Verify that DTC P2122, P2123, 2127, P2128, or P2138 is not set.
- If any of the DTCs are set
Refer to Circuit/System Testing
- Go to next step: If none of the DTCs set
6. Operate the vehicle within the Conditions for Running the DTC. You may
also operate the vehicle
within the conditions that you observed from the Freeze Frame/Failure Records
data.
7. Verify the DTC does not set.
Refer to Circuit/System Testing
- Go to next step: If the DTC does not set
8. All OK
Circuit/System Testing
1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector
at the B107
Accelerator Pedal Position Sensor. It may take up to 2 min for all vehicle
systems to power down.
2. Test for less than 5 Ω between the appropriate low reference circuit terminal
listed below and
ground.
- APP sensor 1 low reference circuit terminal 4
- APP sensor 2 low reference circuit terminal 5
- If 5 Ω or greater
- Ignition OFF, disconnect the harness connector at the K20 Engine Control
Module.
- Test for less than 2 Ω in the low reference circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K20 Engine Control Module.
- Go to next step: If less than 5 Ω
3. Ignition ON.
4. Test for 4.8 - 5.2 V between the appropriate 5 V reference circuit terminal
listed below and
ground.
- APP sensor 1 5 V reference circuit terminal 2
- APP sensor 2 5 V reference circuit terminal 1
- If less than 4.8 V
- Ignition OFF, disconnect the harness connector at the K20 Engine Control
Module.
- Test for infinite resistance between the 5 V reference circuit and
ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the 5 V reference circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K20 Engine Control Module.
- Ignition OFF, disconnect the harness connector at the K20 Engine Control
Module, ignition
ON.
- Test for less than 1 V between the 5 V reference circuit and ground.
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K20 Engine Control Module.
- Go to next step: If between 4.8 - 5.2 V
5. Verify the scan tool APP sensor 1 and APP sensor 2 voltage parameters are
less than 0.3 V.
- Ignition OFF, disconnect the harness connector at the K20 Engine Control
Module, ignition
ON.
- Test for less than 1 V between the signal circuit terminal listed below
and ground.
- APP sensor 1 signal circuit terminal 3
- APP sensor 2 signal circuit terminal 6
- If 1 V or greater, repair the short to voltage on the circuit.
- If less than 1 V, replace the K20 Engine Control Module.
- Go to next step: If less than 0.3 V
6. Install a 3 A fused jumper wire between the appropriate signal circuit
terminal listed below and
the 5 V reference circuit terminal 1.
- APP sensor 1 signal circuit terminal 3
- APP sensor 2 signal circuit terminal 6
7. Verify the scan tool APP sensor 1 or APP sensor 2 voltage parameter is
greater than 4.8 V.
- Ignition OFF, disconnect the harness connector at the K20 Engine Control
Module.
- Test for infinite resistance between the signal circuit terminal and
ground.
- If less than infinite resistance, repair the short to ground on the
circuit.
- Go to next step: If infinite resistance
- Test for less than 2 Ω in the signal circuit end to end.
- If 2 Ω or greater, repair the open/high resistance in the circuit.
- If less than 2 Ω, replace the K20 Engine Control Module.
- Go to next step: If greater than 4.8 V
8. Test or replace the B107 Accelerator Pedal Position Sensor.
Repair Instructions
Perform the Diagnostic Repair Verification after completing the repair.
- Accelerator Pedal with Position Sensor Assembly Replacement
- Control Module References for engine control module replacement,
programming, and setup
READ NEXT:
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.
Diag
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.
Diagnosti
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.
Diagnosti
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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.
Refer to Diagnostic Procedure Instructions for an overview of each
diagnostic category.
DTC Descripto