GM/Detroit 6.5L ENGINE CONTROLS – DTC P1654 Service Throttle Soon Lamp Control CKT

C ircuit 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 Setting the DTC
• The voltage on the Service Throttle Soon lamp control circuit is high (near battery voltage) when the EGR vent is requested ON.
or
• The voltage on the Service Throttle Soon lamp control circuit is low (near 0 volts) when the EGR vent is requested OFF.

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.
2. Be sure that both the ON and the OFF states are commanded. Repeat the commands as many times as necessary.
9. 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.

 

Leave a Reply

Your email address will not be published. Required fields are marked *