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For 1990-2009 cars only

DTC P1288 Without RPO CTF

Table 1: APP Sensor Position Table

Circuit Description

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of 3 individual sensors within 1 housing. Three separate signal, low reference, and 5-volt reference circuits are used in order to interface the APP sensor with the engine control module (ECM). Each sensor has a unique functionality to determine pedal position as shown in the table below. The ECM uses the APP sensor to determine the amount of acceleration or deceleration desired by the person driving the vehicle via fuel injector control. This DTC sets if the ECM determines an out of range condition with the APP sensor.

APP Sensor Position Table

APP Sensor

Actual Pedal Position

% Depressed as Observed on a Scan Tool

Voltage as Observed on a Scan Tool

1

Pedal at rest

0

.52 - .80

1

Pedal at full travel

100

2.12 - 2.78

2

Pedal at rest

0

4.25 - 4.53

2

Pedal at full travel

100

2.24 - 2.93

3

Pedal at rest

0

3.95 - 4.13

3

Pedal at full travel

100

2.69 - 3.16

Conditions for Running the DTC

    • DTCs P0641 or P0651 are not set.
    • The ignition switch is in the crank or run position.
    • The ignition voltage is between 7-16 volts.

Conditions for Setting the DTC

    • The APP sensor 3 voltage is more than 4.75 volts.
    • All of the above conditions are present for less than 1 second.

Action Taken When the DTC Sets

    • The control module stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • If one or more APP sensor DTCs are set for a single APP sensor, the control module will use the remaining two APP sensors to calculate throttle response.
    • If certain multiple APP sensor DTCs are set for more than one APP sensor, the following occurs:
       - The control module commands Reduced Engine Power mode.
       - The APP indicated angle is limited to a predetermined value to limit the amount of throttle control.
    • If all three APP sensors are out of range, the APP indicated angle is limited to 0 percent. The control module only allows the engine to idle.

Conditions for Clearing the DTC

    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • Clear the DTC with a scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Observe the Freeze Frame/Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text or as close to the Freeze Frame/Failure Records data that you observed.

Does the DTC fail this ignition?

--

Go to Step 4

Go to Step 3

3

  1. Select the Diagnostic Trouble Code (DTC) option on the scan tool.
  2. Lightly touch and move the related accelerator pedal position (APP) sensor wiring harnesses and connectors while monitoring the DTC Information.

Did this DTC fail this ignition, during the above test?

--

Go to Step 9

Go to Intermittent Conditions

4

  1. Disconnect the APP sensor harness connector.
  2. With a DMM, measure voltage at the APP sensor 3 signal circuit.

Does the DMM indicate voltage at the specified value?

5.05 V

Go to Step 5

Go to Step 6

5

  1. Connect a fused jumper between the APP sensor 2 signal circuit and the APP sensor 3 low reference circuit.
  2. With a scan tool, observe the APP sensor 2 voltage parameter.

Does the scan tool indicate APP sensor 2 voltage at the specified value?

0 V

Go to Step 11

Go to Step 9

6

  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) harness connector containing the APP sensor 3 signal circuit.
  3. Test the APP sensor 3 signal circuit for an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 7

7

  1. Turn ON the ignition.
  2. Test the APP sensor  3 signal circuit for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 8

8

  1. Turn OFF the ignition.
  2. Disconnect the ECM harness connectors.
  3. Test the APP sensor 3, signal circuit for a short to all other APP circuits at the APP sensor harness connector. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

9

  1. Disconnect the ECM harness connector containing the APP sensor 3 low reference circuit.
  2. Test the APP sensor 3 low reference circuit for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 12

10

Repair the intermittent condition as necessary. Refer to Connector Repairs , and Wiring Repairs in Wiring Systems.

Did you complete the repair?

--

Go to Step 15

--

11

Inspect for poor connections at the harness connector of the APP sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 13

12

Inspect for poor connections at the harness connector of the ECM. Refer to Testing for Intermittent Conditions and Poor Connections and Repairing Connector Terminals in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 15

Go to Step 14

13

Replace the APP sensor assembly.

Did you complete the replacement?

--

Go to Step 15

--

14

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

--

Go to Step 15

--

15

  1. Use a scan tool to clear the DTCs.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 16

Go to Step 2

16

With a scan tool, observe the stored information, Capture Info.

Does the scan tool display any DTCs that you have not diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK

DTC P1288 With RPO CTF

Circuit Description

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal control assembly. The sensor is made up of three individual sensors within one housing. The engine control module (ECM) uses the APP sensors to determine the amount of acceleration or deceleration desired by the person driving the vehicle via the fuel injector control. The APP sensor 3 has the following circuits:

    • A 5-volt reference circuit
    • A low reference circuit
    • An APP sensor 3 signal circuit

The ECM supplies 5 volts to the APP sensor 3 on the 5-volt reference circuit. The ECM also provides a ground on the low reference circuit. The APP sensor 3 provides a signal to the ECM on the APP sensor 3 signal circuit which is relative to the position changes of the accelerator pedal angle. The ECM monitors the APP sensor 3 signal for voltage outside the normal range of the APP sensor 3. If the ECM detects an excessively high APP sensor 3 signal voltage, this DTC will set.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The APP sensor 3 voltage is more than 4.75 volts.

Action Taken When the DTC Sets

    • The ECM does not illuminate the malfunction indicator lamp (MIL) when the diagnostic runs and tails.
    • The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.

Condition for Clearing the DTC

    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the DTC with a scan tool.

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Engine Controls?

--

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn OFF the ignition for 30 seconds.
  2. Start the engine.
  3. Observe the APP Sensor 3 parameter with a scan tool.

Is the APP Sensor 3 parameter more than the specified value?

4.75 V

Go to Step 4

Go to Step 3

3

  1. Observe the Failure Records data for this DTC.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Failure Records.

Did the DTC fail this ignition?

--

Go to Step 4

Go to Intermittent Conditions

4

  1. Start the engine.
  2. Monitor the Diagnostic Trouble Code (DTC) Information with a scan tool.

Is DTC P1646 also set?

--

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the APP sensor 3 parameter with a scan tool.

Is the APP sensor 3 parameter less than the specified value?

0.25 V

Go to DTC P1646

Go to Step 8

6

  1. Turn OFF the ignition.
  2. Disconnect the APP sensor connector.
  3. Turn ON the ignition, with the engine OFF.
  4. Observe the APP sensor 3 parameter with a scan tool.

Is the APP sensor 3 parameter less than specified value?

4.75 V

Go to Step 8

Go to Step 7

7

  1. Turn OFF the ignition.
  2. Disconnect the APP sensor connector.
  3. Connect a DMM between the 5-volt reference circuit and the low reference circuit of the APP sensor 3.
  4. Turn ON the ignition, with the engine OFF.

Is the DMM voltage within the specified range?

4.5-5.5 V

Go to Step 8

Go to Step 9

8

    Important: The APP sensor 3 may be damaged if the circuit short to voltage source.

  1. Test the signal circuit between the engine control module (ECM) and the APP sensor 3 for the following conditions:
  2. • A short to voltage circuit
    • An open circuit
  3. Repair the circuits, as necessary.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

9

  1. Test the low reference circuit between the ECM and the APP sensor 3 for the following conditions:
  2. • An open circuit
    • High resistance
  3. Repair the circuits as necessary.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 11

10

  1. Turn OFF the ignition.
  2. Disconnect the APP sensor connector.
  3. Inspect for poor connections at the harness connector of the APP sensor 3.
  4. Repair the connections as necessary.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 12

11

  1. Turn OFF the ignition.
  2. Disconnect the ECM.
  3. Inspect for poor connections at the harness connector of the ECM.
  4. Repair the connections, as necessary.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 13

12

Replace the APP sensor. Refer to Accelerator Pedal Position Sensor Replacement .

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data .

Did you complete the replacement?

--

Go to Step 14

--

14

  1. Clear the DTCs with a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Failure Records.

Did the DTC fail this ignition?

--

Go to Step 2

Go to Step 15

15

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

--

Go to Diagnostic Trouble Code (DTC) List

System OK