GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Savana 🢒 Body and Accessories 🢒 Theft Deterrent 🢒 DTC P1654

Circuit Description

A dash light is illuminated by the powertrain control module (PCM) if the diagnostic has detected certain errors related to the accelerator pedal position (APP) sensor. When the PCM is commanding the service throttle soon lamp ON, the voltage potential of the circuit will be low, near 0 volts. When the PCM is commanding the service throttle soon lamp OFF, the voltage potential of the circuit will be high, near the battery voltage. The primary function of the PCM in this circuit is to supply the ground for the service throttle soon lamp.

Conditions for Running the DTC

The ignition is in the ON position.

Conditions for Setting the DTC
    • The service throttle soon lamp is requested ON.
    • The voltage on the service throttle soon control circuit is high, near the battery voltage.

or

    • The service throttle soon lamp is requested OFF.
    • The voltage on the service throttle soon control circuit is low, near 0 volts.

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.
    • The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC
    • A current DTC Last Test Failed clears when the diagnostic runs and passes.
    • A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
    • Clear the DTC with a scan tool.

Diagnostic Aids

A malfunctioning bulb or the control circuit is shorted to ground will cause a DTC P1654 to set.

Test Description

The number below refers to the step number on the diagnostic table.

  1. This step tests the ON and the OFF states.

Step

Action

Yes

No

Schematic Reference: Engine Controls Schematics

1

Important: Before clearing the DTCs, use the scan tool Capture Info to save the Freeze Frame/Failure Records for reference. The data in the control module is deleted once the Clear Info function is used.

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

  1. Turn ON the ignition, with the engine OFF.

    2. Important: Ensure that both the ON and the OFF states are commanded. Repeat the commands as many times as necessary.

  2. Use a scan tool in order to command the lamp ON and OFF.

Does the lamp turn ON and OFF with each command?

Go to Step 3

Go to Step 4

3

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs are stored, refer to those tables.

Are there any additional DTCs stored?

Go to Diagnostic Trouble Code (DTC) List

Go to Diagnostic Aids

4
  1. Turn OFF the ignition.
  2. Disconnect the PCM connector containing the lamp control circuit.
  3. Turn ON the ignition, with the engine OFF.

Is the lamp OFF?

Go to Step 5

Go to Step 7

5

With a fused jumper wire connected to ground, probe the lamp control circuit in the PCM harness connector.

Does the lamp illuminate?

Go to Step 6

Go to Step 8

6
  1. Inspect for poor connections at the PCM.
  2. If a problem is found, repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

Go to Step 10

Go to Step 9

7

The service throttle soon lamp control circuit is shorted to ground. Repair as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you complete the repair?

Go to Step 10

--

8
  1. Inspect the service throttle soon circuit for the following conditions:
    2. • An open ignition feed to the bulb
    • A malfunctioning bulb
    • The control circuit open or shorted to B+
  2. Repair the problem as necessary. Refer to Wiring Repairs in Wiring Systems.

Did you perform a repair?

Go to Step 10

--

9

Replace the PCM. Refer to Powertrain Control Module Replacement .

Did you complete the replacement?

Go to Step 10

--

10
  1. Use the scan tool in order to clear the DTCs.
  2. Start the engine.
  3. Allow the engine to idle until the engine reaches the normal operating temperature.
  4. Select DTC and the Specific DTC function.
  5. Enter the DTC number that was set.
  6. Operate the vehicle within the Conditions for Setting this DTC until the scan tool indicates the diagnostic ran.

Does the scan tool indicate the diagnostic passed?

Go to Step 11

Go to Step 2

11

Does the scan tool display any additional undiagnosed DTCs?

Go to Diagnostic Trouble Code (DTC) List

System OK