engine surge- throttle warning light

hey everyone i hope someone can help me. i have a 98 chevy k3500
4x4 auto tranny 6.5 turbo diesel. my engine speeded up all of a sudden
for no reason. i got home and a light on the dash came on that said
service throttle soon. do i replace accelerator pedal module or
throttle position sensor. where is the throttle position sensor located.

thanks for any help

steve n.carolina

The APP (pedal module) is the throttle position sensor. There are no other "throttle position sensors". The pump is electronic, with all moving parts internal.

Check the connectors and harness before anything else. The "Service Throttle Soon" indicates a loss of communication with the APP, or input values out of spec. If this is the first time you've seen this lamp, and you have immediate issues (engine surge w/ the lamp), a connection problem is likely. Try cleaning the contacts and reconnecting the connector.

The APP module has 3 internal independent circuits, and 3 stages of fault:

Lose 1 circuit = STS lamp only, and possible delayed or unusual throttle response;
Lose 2 circuits = STS lamp and limp mode;
Lose all 3 circuits = STS lamp and no throttle response.

If the APP module is at fault, don't try to repair it, unless absolutely necessary. There are methods of "cleaning", which often result in a functional APP, but this should be considered a temporary repair, and unreliable. The APP's are extremely reliable (normally), so a used replacement (vs. new) is not a bad idea, and a lot less expensive.

i really needed the help here. im new to chevy diesel.

thanks a bunch have a great day

steve n.carolina

Quote:

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Originally Posted by DmaxMaverick

The APP (pedal module) is the throttle position sensor. There are no other "throttle position sensors". The pump is electronic, with all moving parts internal.

Check the connectors and harness before anything else. The "Service Throttle Soon" indicates a loss of communication with the APP, or input values out of spec. If this is the first time you've seen this lamp, and you have immediate issues (engine surge w/ the lamp), a connection problem is likely. Try cleaning the contacts and reconnecting the connector.

The APP module has 3 internal independent circuits, and 3 stages of fault:

Lose 1 circuit = STS lamp only, and possible delayed or unusual throttle response;
Lose 2 circuits = STS lamp and limp mode;
Lose all 3 circuits = STS lamp and no throttle response.

If the APP module is at fault, don't try to repair it, unless absolutely necessary. There are methods of "cleaning", which often result in a functional APP, but this should be considered a temporary repair, and unreliable. The APP's are extremely reliable (normally), so a used replacement (vs. new) is not a bad idea, and a lot less expensive.

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My son just had this happen to him yesterday. He had to go about 10 miles at idle to get it home. The STS light came on but it did not throw any codes. I hopped in it today and everything worked fine. Should I clean the connections at the pedal? Are there other connections in the harness I should check?

Thanks.