GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2003 🢒 Kodiak C-Series (Conventional) C6/C7/C8 🢒 DTC 🢒 DTC P1646

DTC P1646 Without RPO CTF

Circuit Description

The engine control module (ECM) provides 5 volts for the accelerator pedal position (APP) sensor 3.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC
    • The circuit voltage is more than 5.5 volts.
    • The circuit voltage is less than 4.5 volts.
    • The above conditions are met for 0.7 seconds.

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

Conditions for Clearing the MIL/DTC
    • The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
    • A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
    • Clear the MIL and the DTC with a scan tool.

Diagnostic Aids

Inspect for the following conditions:

    • A poor connection at the ECM connector
    • A poor connection at the battery connector
    • A harness short
    • A defect at the sensor

Step

Action

Values

Yes

No

Schematic Reference: Engine Controls Schematics

1

Did you perform the Diagnostic System Check-Engine Controls?

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Go to Step 2

Go to Diagnostic System Check - Engine Controls

2
  1. Turn the ignition ON.
  2. Clear the DTCs.
  3. Turn the ignition OFF for 30 seconds.
  4. Turn the ignition ON.

Does the scan tool display the DTC?

--

Go to Step 3

Go to Intermittent Conditions

3
  1. Turn the ignition OFF.
  2. Disconnect the APP 3 sensor.
  3. Turn the ignition ON.
  4. Measure the voltage of the APP 3 sensor 5-volt reference circuit.

Does the voltage measure within the specified range?

4.5-5.5 V

Go to Step 4

Go to Step 6

4
  1. Disconnect the APP sensor.
  2. Measure the resistance of the APP 3 sensor with a DMM.
  3. Depress the accelerator pedal while observing the resistance of the APP 3 sensor.

Does the resistance of the APP 3 sensor change while moving the accelerator pedal?

--

Go to Step 6

Go to Step 5

5

Replace the APP sensor.

Did you complete the replacement?

--

Go to Step 8

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6

Inspect for the following conditions:

    • A poor connection at the APP sensor or the ECM.
    • An open in the APP sensor harness.
    • A short to ground in the APP sensor harness.
    • A short to voltage in the APP sensor harness.

Did you find and correct the condition?

--

Go to Step 8

Go to Step 7

7

Replace the ECM.

Did you complete the replacement?

--

Go to Step 8

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8
  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 as specified in the supporting text.

Does the DTC run and pass?

--

Go to Step 9

Go to Step 2

9

Observe the stored information, Capture Info with a scan tool.

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

--

Go to Diagnostic Trouble Code (DTC) List

System OK