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51A5






51A5-IMPLAUSIBLE ACCELERATOR PEDAL MESSAGE RECEIVED

For a complete wiring diagram, Refer to the Wiring Information Electrical Diagrams.

- When Monitored:
With the ignition on and no APPS No.1 and APPS No.2 DTC present.

- Set Condition:
APPS values No.1 and No.2 are not coherent. Idle is additionally forced when the brake pedal is pressed or failed. Acceleration rate and Engine output are limited. One trip fault and the code will set within 5 seconds. ETC light is flashing.





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

1. ACTIVE DTC
1. Start the engine and allow it to reach normal operating temperature.

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 may result in possible serious or fatal injury.

NOTE: Diagnose and repair any system voltage or sensor supply voltage DTCs before continuing with this test.

NOTE: If you are viewing data recorder information or Freeze Frame data the APP Sensor No. 2 is pulled low by the ECM 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

- Perform the INTERMITTENT CONDITION Diagnostic Procedure. .

2. EXCESSIVE RESISTANCE IN THE APPS NO.1 SIGNAL CIRCUIT
1. Turn the ignition off.
2. Using a voltmeter perform a voltage drop test. Backprobe the APPS No.1 Signal circuit at the APPS harness connector and probe the ECM harness connector. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 3

No

- Repair the excessive resistance in the APP Sensor No.1 Signal circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

3. EXCESSIVE RESISTANCE IN THE SENSOR NO.1 RETURN CIRCUIT
1. Turn the ignition off.
2. Move the voltmeter leads to backprobe the APPS No.1 Return circuit at the APPS harness connector and probe the ECM harness connector. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 4

No

- Repair the excessive resistance in the Sensor No.1 Return circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

4. EXCESSIVE RESISTANCE IN THE APPS NO.2 SIGNAL CIRCUIT
1. Turn the ignition off.
2. Move the voltmeter leads to backprobe the APPS No.2 Signal circuit at the APPS harness connector and probe the ECM harness connector. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 5

No

- Repair the excessive resistance in the APP Sensor No.2 Signal circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

5. EXCESSIVE RESISTANCE IN THE SENSOR NO.2 RETURN CIRCUIT
1. Turn the ignition off.
2. Move the voltmeter leads to backprobe the APPS No.2 Return circuit at the APPS harness connector and the ECM harness connector. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 6

No

- Repair the excessive resistance in the Sensor No.2 Return circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

6. EXCESSIVE RESISTANCE IN THE 5-VOLT SUPPLY CIRCUIT
1. Turn the Ignition off.
2. Using a voltmeter perform a voltage drop test. Backprobe the 5-volt Supply circuit at the APPS harness connector and the ECM harness connector.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 7

No

- Repair the excessive resistance in the 5-volt Supply circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

7. EXCESSIVE RESISTANCE IN THE 5-VOLT SUPPLY CIRCUIT
1. Turn the Ignition off.
2. Using a voltmeter perform a voltage drop test. Backprobe the 5-volt Supply circuit at the APPS harness connector and probe the ECM harness connector. Make sure the voltmeter leads are connected so a positive polarity is displayed on the voltmeter.

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 may result in possible serious or fatal injury.

3. Start the engine and allow it to reach normal operating temperature.
4. Monitor the voltmeter.

Is the voltage below 0.5 of a volt?

Yes

- Go To 8

No

- Repair the excessive resistance in the 5-volt Supply circuit.
- Perform the ECM VERIFICATION TEST Verification Tests.

8. CHECKING APPS NO.1 AND NO.2 WITH A LAB SCOPE
1. Turn the Ignition off.
2. Ignition on, engine not running.
3. Set up a lab scope in a way that you can view two graphs simultaneously.
4. Backprobe APP Sensor No.1 Signal circuit using Channel 1 at the APP Sensor harness connector.
5. Backprobe APP Sensor No.2 Signal circuit using Channel 2 at the APP Sensor harness connector.

NOTE: The APP Sensor No. 2 is pulled low by the ECM 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. It is acceptable to see the voltage close to zero with a normal sensor when using a data recorder/lab scope.

6. Slowly press and release the Accelerator Pedal while monitoring the lab scope screen.

Does the scope pattern show any missing or erratic signals?

Yes

- Replace the APP Sensor Assembly. After installation is complete, use a scan tool and select the ETC RELEARN function to relearn the APPS values.
- Perform the ECM VERIFICATION TEST Verification Tests.

No

- Go To 9

9. ECM

NOTE: Before continuing, check the ECM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

1. Using the schematics as a guide, inspect the wire harness and connectors. Pay particular attention to all Power and Ground circuits.

Were there any problems found?

Yes

- Repair as necessary.
- Perform the ECM VERIFICATION TEST Verification Tests.

No

- Replace and program the Engine Control Module.
- Perform the ECM VERIFICATION TEST Verification Tests.

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