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P2123






P2123-ACCELERATOR PEDAL POSITION SENSOR 1 CIRCUIT HIGH

For a complete wiring diagram, refer to the Wiring Information.





Theory of Operation

The Electronic Throttle Control (ETC) system uses two Accelerator Pedal Position (APP) Sensors to monitor the accelerator pedal position. The APP Sensors 1 and 2 are integrated into one assembly located at the pedal assembly. Each sensor has a 5-volt reference circuit, a low reference circuit, and a signal circuit. The Powertrain Control Module (PCM) reads the two signals individually and then compares the two signals as a redundant check of the throttle position. One of the sensors will fluctuate between 0 volts and 5.0 volts and the other sensor will fluctuate between 0 volts and 2.5 volts. The fluctuation of the two sensors should move proportionately. E.G. When operating properly, the voltage reading of the sensor operating on the 5.0 volt scale will always approximately two time the voltage reading of the sensor on the 2.5 volts scale.

- When Monitored:
With the ignition on.

- Set Condition:
When the APP Sensor No.1 voltage is above 4.8 volts for 0.5 seconds. Acceleration rate and Engine output are limited. One trip fault. ETC light is flashing.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

Diagnostic Test

1. ACTIVE DTC

NOTE: When this DTC is Active the engine speed, torque and vehicle speed are limited to a Limp in mode.

1. Turn the ignition on.

WARNING:
When the engine is operating, do not stand in direct line with the fan. Do not put your hands near the pulleys, belts, or fan. Do not wear loose clothing. Failure to follow these instructions can result in possible serious or fatal injury.

NOTE: If there are any 5-Volt Reference DTCs present, diagnose and repair those DTCs before continuing with this test procedure.

NOTE: If you are viewing data recorder information or Freeze Frame data the APP Sensor No. 2 is pulled low by the PCM as part of its system testing. This test happens every 320 milliseconds and may not show up on the scan tool but may show up on a data recorder or lab scope. It is acceptable to see the voltage close to zero with a normal sensor when using a data recorder/lab scope.

2. With the scan tool, select View DTCs.

Is the DTC Active at this time?

Yes

- Go To 2

No

- Go To 8

2. CHECK THE (K23) APP SENSOR NO.1 SIGNAL CIRCUIT FOR A SHORT TO VOLTAGE
1. Turn the ignition off.
2. Disconnect the APP Sensor harness connector.
3. Turn the ignition on.
4. Measure the voltage on the (K23) APP Sensor No.1 Signal circuit at the APP Sensor harness connector.

Is the voltage above 5.2 volts?

Yes

- Repair the APP Sensor No.1 Signal circuit for a short to voltage.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 3

3. CHECK FOR THE (K23) APPS NO.1 SIGNAL CIRCUIT SHORTED TO THE (K852) 5-VOLT SUPPLY CIRCUIT
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.
3. Measure the resistance between the (K23) APP Sensor No.1 Signal circuit and the (K852) 5-Volt Supply circuit at the APP Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 4

No

- Repair the short between the (K23) APP Sensor No.1 Signal circuit and the (K852) 5-Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

4. CHECK FOR THE (K23) APPS NO.1 SIGNAL CIRCUIT SHORTED TO THE (K854) 5-VOLT SUPPLY CIRCUIT
1. Measure the resistance between the (K23) APP Sensor No.1 Signal circuit and the (K854) 5-Volt Supply circuit at the APP Sensor harness connector.

Is the resistance above 10k Ohms?

Yes

- Go To 5

No

- Repair the short between the (K23) APP Sensor No.1 Signal circuit and the(K854) 5-Volt Supply circuit.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

5. CHECK THE (K167) APP SENSOR NO.1 RETURN CIRCUIT FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (K23) APP Sensor No.1 Signal circuit and the between the APP Sensor harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 6

No

- Repair the (K167) APP Sensor No.1 Return circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

6. ACCELERATOR PEDAL POSITION SENSOR
1. Reconnect the PCM C1 harness connector.
2. Connect a jumper between the (K23) APP Sensor No.1 Signal circuit and the (K167) APP Sensor No.1 Return circuit and the.
3. Turn the ignition on.
4. With the scan tool, monitor the APP Sensor No. 1 voltage.

Does the voltage read 0 volts?

Yes

- Verify that there is good pin to terminal contact in the APP Sensor and Powertrain Control Module connectors. If OK, replace the Accelerator Pedal Position Sensor Assembly. Removal. After installation is complete, use a scan tool and perform the Reset Accelerator Pedal Adaptives to relearn the APPS values.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Go To 7

7. POWERTRAIN CONTROL MODULE (PCM)
1. Using the wiring diagram/schematic as a guide, inspect the wiring and connectors between the Accelerator Pedal Position Sensor and the Powertrain Control Module (PCM).
2. Look for any chafed, pierced, pinched or partially broken wires.
3. Look for broken, bent, pushed out or corroded terminals. Verify that there is good pin to terminal contact in the APP Sensor and Powertrain Control Module harness connectors.
4. Perform any Technical Service Bulletins that may apply.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

No

- Replace and program the Powertrain Control Module. .
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

8. APP SENSOR NO.1 SWEEP
1. Turn the ignition on, engine not running.
2. With the scan tool, monitor the Accelerator Pedal Position Sensor voltage.
3. Slowly press the Accelerator Pedal down.

Does voltage start at approximately 0.45 volts and go to approximately 4.6 volts with a smooth transition?

Yes

- Perform the INTERMITTENT CONDITION diagnostic procedure. Intermittent Condition Test.

No

- Verify that there is good pin to terminal contact in the APP Sensor and Powertrain Control Module connectors. If OK, replace the Accelerator Pedal Position Sensor Assembly. Removal. After installation is complete, use a scan tool and perform the Reset Accelerator Pedal Adaptives to relearn the APPS values.
- Perform the POWERTRAIN VERIFICATION TEST. Powertrain Verification Test.

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