DTC P2122, P2123, P2127, P2128, or P2138 (LLU)
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DTC P2122, P2123, P2127, P2128, or P2138 (LLU)
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DTC P2122 00
Accelerator Pedal Position (APP) Sensor 1 Circuit Low Voltage
DTC P2123 00
Accelerator Pedal Position (APP) Sensor 1 Circuit High Voltage
DTC P2127 00
Accelerator Pedal Position (APP) Sensor 2 Circuit Low Voltage
DTC P2128 00
Accelerator Pedal Position (APP) Sensor 2 Circuit High Voltage
DTC P2138 00
Accelerator Pedal Position (APP) Sensors 1-2 Not Plausible
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Diagnostic Fault Information
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Circuit
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Short to Ground
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Open/High Resistance
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Short to Voltage
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Signal Performance
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5V Reference Sensor 1 Circuit
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P2122 00
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P2122 00, P2138 00
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P2122 00, P2135 00
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P2138 00
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5V Reference Sensor 2 Circuit
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P2127 00
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P2127 00, P2138 00
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P2127 00, P2138 00
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P2138 00
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Signal Circuit Sensor 1
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P2122 00
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P2122 00, P2138 00
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P2123 00
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P2138 00
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Signal Circuit Sensor 2
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P2122 00
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P2122 00, P2138 00
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P2123 00
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P2138 00
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Low Reference Sensor 1
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-
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P2123 00, P2138 00
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-
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P2138 00
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Low Reference Sensor 2
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-
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P2127 00, P2128 00, P2138 00
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-
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P2138 00
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APP Sensor 1 and 2
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Circuit
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Short to Ground
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Open
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Short to Voltage
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Operating Conditions:
The engine is operating at idling speed.
Parameter Normal Range:
APP Sensor 1-0.88-1.08 V
Parameter Normal Range:
APP Sensor 2-0.39-0.59 V
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5V Reference Sensor 1
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0.00 V
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0.00 V
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2.75 V
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5V Reference Sensor 2
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0.00 V
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0.00 V
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1.35 V
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Signal Circuit Sensor 1
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0.00 V
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0.00 V
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4.98 V
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Signal Circuit Sensor 2
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0.00 V
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0.00 V
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4.98 V
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Low Reference Sensor 1
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-
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4.96 V
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-
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Low Reference Sensor 2
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-
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4.92 V
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-
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Circuit/System Description
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The accelerator pedal assembly contains 2 accelerator pedal position (APP) sensors. The APP sensors are mounted on the accelerator pedal assembly and are not serviceable. The APP sensors send a signal voltage that changes relative to the 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.
Both the percentages for APP sensor signals 1 and 2 increase when the pedal is pressed. From about 0 % in rest position to over 95 % fully pressed.
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Conditions for Running the DTC
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P2122 00, P2123 00, P2127 00, P2128 00
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•
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The ignition voltage is greater than 8 V.
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The ECM is not commanding reduced power.
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The DTCs run continuously when the above conditions are met.
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P2138 00
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DTCs P2122 00, P2123 00, P2127 00, or P2128 00 are not set.
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The ignition voltage is greater than 8 V.
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The ECM is not commanding reduced power.
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The accelerator pedal is not in the rest position.
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The DTC runs continuously when the above conditions are met.
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Conditions for Setting the DTC
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P2122 00
The ECM detects that the APP sensor 1 voltage is less than 0.82 V for less than 1 s.
P2123 00
The ECM detects that the APP sensor 1 voltage is greater than 4.7 V for less than 1 s.
P2127 00
The ECM detects that the APP sensor 2 voltage is less than 0,58 V for less than 1 s.
P2128 00
The ECM detects that the APP Sensor 2 voltage is greater than 4.8 V for less than 1 s.
P2138 00
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The voltage difference between APP sensor 1 and APP sensor 2 exceeds a predetermined value for more than 2 s.
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The ECM detects that the voltage difference between APP sensor 1 and the calculated idle range is greater than 0.23 V, with a released pedal.
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The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 0.29 V with a partially pressed pedal.
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The ECM detects that the voltage difference between APP sensor 1 and 2 is greater than 1.75 V with a fully pressed pedal.
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Any of the above conditions exist for greater than 1 s, or a cumulative of 10 s.
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Action Taken When the DTC Sets
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DTCs P2122 00, P2123 00, P2127 00, P2128 00, and P2138 00 are Type C DTCs.
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The ECM commands the throttle actuator control system to operate in reduced engine power mode.
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The service vehicle soon indicator will illuminate.
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Under certain conditions, the engine control module commands the engine OFF.
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Conditions for Clearing the DTC
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DTCs P2122 00, P2123 00, P2127 00, P2128 00, and P2138 00 are Type C DTCs.
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If a shared 5 V reference circuit is shorted to ground or shorted to a voltage, other 5 V reference circuits may be affected.
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A high resistance condition on the accelerator pedal position (APP) sensor circuits may cause a DTC to set.
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Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Description and Operation
Throttle Actuator Control (TAC) System Description (LLU)
Electrical Information Reference
DTC Type Reference
Powertrain Diagnostic Trouble Code (DTC) Type Definitions
Scan Tool Reference
Control Module References
for scan tool information
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Circuit/System Verification
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1.
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Ignition ON, observe the DTC information with a scan tool. Verify no DTCs are set.
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3.
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Ignition ON, check the scan tool voltage parameter for APP sensors 1 and 2. Verify that the voltage parameters for both APP sensor 1 and APP sensor 2 are between 0.4 V and 4.5 V.
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4.
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Rapidly depress the accelerator pedal from the rest position to the wide open throttle position (WOT) and release pedal. Repeat the procedure several times. DTC P2122 00, P2123 00, P2127 00, P2128 00, or P2138 00 should not be generated.
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5.
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Slowly depress the accelerator pedal to WOT and then slowly return the pedal to closed throttle. Repeat the procedure several times. DTC P2122 00, P2123 00, P2127 00, P2128 00, or P2138 00 should not be generated.
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6.
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Operate the vehicle within the conditions for running the DTC to verify the DTC does not reset. You may also operate the vehicle within the conditions that you observed from the freeze frame/failure records data.
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1.
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Ignition OFF, disconnect the B107 Accelerator Pedal Position Sensor harness connector at the accelerator pedal assembly.
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2.
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Ignition OFF for 1 min, test for less than 5 Ω between the B107 Accelerator Pedal Position Sensor low reference circuit terminals listed below and ground.
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Low reference circuit terminal 4
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Low reference circuit terminal 5
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If greater than the specified range, test the low reference circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
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3.
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Ignition ON, test for 4.8-5.2 V between both 5 V reference circuit terminals listed below and ground.
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5 V reference circuit terminal 1
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5 V reference circuit terminal 2
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4.
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If less than the specified range, test the 5 V reference circuit for a short to ground or open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
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5.
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If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
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6.
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Verify the scan tool APP Sensor 1 or APP Sensor 2 voltage parameter is at 0 V.
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7.
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If greater than the specified range, test the appropriate signal circuit terminal listed below for a short to voltage. If the circuit tests normal, replace the K20 Engine Control Module.
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APP sensor 1 signal circuit terminal 3
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APP sensor 2 signal circuit terminal 6
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8.
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Install a 3 A fused jumper wire between the appropriate signal circuit terminal listed below and the 5-volt reference circuit terminal 1 of the B107 Accelerator Pedal Position Sensor. Verify the scan tool APP Sensor 1 or APP Sensor 2 voltage parameter are greater than 4.8 V.
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APP sensor 1 signal circuit terminal 3
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APP sensor 2 signal circuit terminal 6
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9.
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If less than the specified range, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the K20 Engine Control Module.
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10.
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If all circuits test normal, replace the B107 Accelerator Pedal Position Sensor.
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Perform the
Diagnostic Repair Verification
after completing the diagnostic procedure.
