DTC P1654 Service Throttle Soon Lamp Control Circuit. GMC Truck GMC K Pickup

For 1990-2009 cars only

Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC K Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 6.5L 🢒 DTC P1654 Service Throttle Soon Lamp Control Circuit

Engine Controls Components
PWR, GND, and DLC
OBD II Symbol Description Notice
Handling ESD Sensitive Parts Notice
Handling ESD Sensitive Parts Notice

Circuit Description

A dash light is illuminated by the PCM if the diagnostics 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 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 switch in the ON position.

Conditions for Running the DTC

The ignition switch 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 volts).

•	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 PCM will not illuminate the malfunction indicator lamp (MIL).

•	The PCM records the operating conditions at the time the diagnostic fails. This information is stored in the Failure Records.

Conditions for Clearing the MIL/DTC

•	The PCM will turn the MIL off after three consecutive trips without a fault condition.

•	A History DTC clears after forty consecutive warm-up cycles, if this or any other emission related diagnostic does not report any failures

•	The use of a scan tool.

Diagnostic Aids

A faulty bulb or the control circuit shorted to ground will cause a P1654 to set.

Test Description

Number(s) below refer to the step number(s) on the Diagnostic Table.

Be sure that both the ON and the OFF states are commanded. Repeat the commands as many times as necessary.

If no trouble is found in the control circuit or the connections at the PCM, the PCM maybe malfunctioning, however, this is an extremely unlikely failure.

Step

Action

Value(s)

Yes

Important: Before clearing any DTCs, use the scan tool Capture Info to save freeze frame and failure records for reference, as the Scan tool loses data when using the Clear Info function.

Was the Powertrain On-Board Diagnostic (OBD) System Check performed?

Go to Step 2

Go to Powertrain On Board Diagnostic (OBD) System Check

Turn the ignition ON leaving the engine OFF.
Using a scan tool, command the lamp ON and OFF.

Does the lamp turn ON and OFF with each command?

Go to Step 3

Go to Step 4

The DTC is intermittent. If no additional DTCs are stored, refer to Diagnostic Aids. If additional DTCs were stored refer to those table(s).

Are any additional DTCs stored?

Go to the Applicable DTC table

Go to Diagnostic Aids

Turn the ignition OFF.
Disconnect the PCM connector containing the lamp control circuit.
Turn the ignition ON leaving the engine OFF.

Is the lamp OFF?

Go to Step 5

Go to Step 7

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

Is the lamp ON?

Go to Step 6

Go to Step 8

Check for proper connections at PCM.
If a problem was found, repair as necessary.

Was a repair performed?

Go to Step 10

Go to Step 9

The Service Throttle Soon lamp control circuit is shorted to ground, repair as necessary.

Is the action complete?

Go to Step 10

Check the Service Throttle Soon circuit for the following:

•	Open ignition feed to the bulb.

•	Malfunctioning bulb.

•	Control circuit open or shorted to B+.

Repair the problem as necessary.

Is the repair complete?

Go to Step 10

Replace the PCM.

Important: The new PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming .

Is the action complete?

Go to Step 10

Using the Scan tool, clear the DTCs.
Start the engine and idle at normal operating temperature.
Select DTC, Specific, then enter the DTC number which was set.
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

Does the Scan tool display any additional undiagnosed DTCs?

Go to the Applicable DTC Table

System OK