GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2007 🢒 Isuzu MD F-Series 🢒 Engine 🢒 Engine Controls and Fuel - 7.8L (LG4) 🢒 DTC P1272
Table 1: APP Sensor Position Table

Circuit Description

The accelerator pedal position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is made up of 3 individual sensors within one housing.

The accelerator pedal position sensor 1, sensor 2, and sensor 3 are potentiometer type sensors, each with the following circuits:

    • A 5-volt reference circuit
    • A low reference circuit
    • A signal circuit

The engine control module (ECM) provides the APP sensors a 5-volt reference circuit and a low reference circuit. The APP sensors then provide the ECM signal voltages proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is high at rest and decreases as the pedal is depressed. The APP sensor 3 signal voltage is high at rest and decreases as the pedal is depressed.

When the ECM detects that the APP sensor 2 signal and the APP sensor 3 signal circuits are out of the correlation, DTC will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P1272 Accelerator Pedal Position (APP) Sensor 2-3 Correlation

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

The APP sensor 2 and APP sensor 3 are more than 10 percent out of range of each other.

Action Taken When the DTC Sets
    • The ECM illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
    • The ECM records the operating conditions at the time the diagnostic fails. The ECM stores this information in the Failure Records.
    • If all 3 APP sensors are out of range, the APP indicated angle is limited to 0 percent. The ECM 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 MIL and the DTC with a scan tool.

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

0.52-0.80

1

Pedal at full travel

100

2.38-2.66

2

Pedal at rest

0

4.20-4.48

2

Pedal at full travel

100

2.34-2.62

3

Pedal at rest

0

3.92-4.09

3

Pedal at full travel

100

2.79-2.96

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check - Vehicle?

Go to Step 2

Go to Diagnostic System Check - Vehicle

2
  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 Freeze Frame/Failure Records.

Does the DTC fail this ignition?

Go to Step 5

Go to Step 3

3
  1. Install a scan tool.
  2. Turn OFF the ignition for 30 seconds.
  3. Start the engine.
  4. Monitor the Diagnostic Trouble Code (DTC) Information with a scan tool.
  5. Fully depress release the accelerator pedal.

Does the DTC fail this ignition?

Go to Step 4

Go to Intermittent Conditions

4

Did DTC P0641, P0651, P1646, P1277 or P1278 also set?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

Go to Step 5

5

Is DTC P1271 also set?

Go to DTC P1271

Go to Step 6

6
  1. Turn OFF the ignition.
  2. Disconnect the accelerator pedal position (APP) sensor harness connector.
  3. Turn ON the ignition.
  4. With a test lamp connected to ground, test for voltage at the APP sensor 3, 5-volt reference circuit.

Does the test lamp illuminate?

Go to Step 7

Go to Step 9

7

With a test lamp connected to ground, test for voltage at the APP sensor 3 signal circuit.

Does the test lamp illuminate?

Go to Step 8

Go to Step 10

8

Connect a test lamp between the APP sensor 3, 5-volt reference circuit and the APP sensor 3 low reference circuit.

Does the test lamp illuminate?

Go to Step 12

Go to Step 11

9
  1. Turn OFF the ignition.
  2. Disconnect the engine control module (ECM) harness connector that contains the APP sensor 3 5-volt reference circuit.
  3. Test the APP sensor 3 5-volt reference circuit for high resistance, with a DMM.

Did you find and correct the condition?

Go to Step 16

Go to Step 14

10
  1. Turn OFF the ignition.
  2. Disconnect the ECM harness connector that contains the APP sensor 3 signal circuit.
  3. Test the APP sensor 3 signal circuit for high resistance, with a DMM.

Did you find and correct the condition?

Go to Step 16

Go to Step 14

11
  1. Turn OFF the ignition.
  2. Disconnect the ECM harness connector that contains the APP sensor 3 low reference circuit.
  3. Test the APP sensor 3 low reference circuit for high resistance, with a DMM.

Did you find and correct the condition?

Go to Step 16

Go to Step 14

12

Inspect for poor connections at the harness connector of the APP sensor.

Did you find and correct the condition?

Go to Step 16

Go to Step 13

13

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

Did you complete the replacement?

Go to Step 16

--

14

Inspect for poor connections at the harness connector of the ECM.

Did you find and correct the condition?

Go to Step 16

Go to Step 15

15

Important: The replacement ECM must be programmed.

Replace the ECM. Refer to Engine Control Module Replacement/Restore Fuel Rate Data , and Fuel Injector Flow Rate Programming .

Did you complete the replacement?

Go to Step 16

--

16
  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 Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 2

Go to Step 17

17

Observe the Capture Info with a scan tool.

Are there any DTCs that have not been diagnosed?

Go to Diagnostic Trouble Code (DTC) List - Vehicle

System OK