P1681 TPS error code

[Fatty2004]

hello all.
I am a new member. Own a 2004 Trailblazer LS 4.2 L6 4x4
My husband installed a new throttle body. Reset as instructed. I drove it up the road and when it reached 20mph it threw on the Reduced Engine Power light. Would not accelerate properly and had a rough idle with a chug a lug sound. Ran the scanner and it throws the code P1681
Driver 5 Line 1

Need a nudge in the right direction!

 

[mrrsm]

Welcome to GMT Nation...

Have your Husband first remove the Negative Battery Cable for at LEAST 30 Minutes and in the mean time have him Disconnect and then Reconnect the Plugs to the Throttle Body Just To Be Sure... Don't let him tell you, "I already DID that..." Nevertheless... Have him do it all over again. Ask him if he went anywhere near the PCM by fiddling with any of the Three Connectors... or perhaps that he decided to install ANOTHER PCM as well and advise us on what he says.

Just an FYI... The P1681 Driver 5 Line 1 is a VERY Specific GM Code indicating that either PCM is BAD or that it has not been properly programmed because it is picking up minor internal Circuit Voltage Differences that it cannot reconcile. This is NOT a Run Of The Mill DTC Error Code.

Anytime any GM Vehicle cannot resolve issues between the MAF Sensor, the Vehicle Speed Sensor, The Throttle Body and-or the Dual Hi-Lo Circuits coming to and from from the ACC Pedal Module (Fake Gas Pedal)... the PCM will Automatically shunt the engine to Reduced Power...for the sake of Driver & Passenger Safety...preventing any chance of having a "Runaway Engine" event and causing an Accident.

 

[TJBaker57]

Here is a screenshot from a GM document for a 2004 4.2 LL8 that states that particular code is for the TPS2 portion of the TPS sensor. The second image shows the wiring for the sensor, TPS2 being ths portion with the blk/wht, ppl, and lt blu/blk wires.

Edit: Could be either TPS1 or TPS2 I guess, though only TPS2 is mentioned in the "Malfunction criteria and Threshold Values" column.

 

[Mooseman]

Edited thread title for better responses and rules compliance.

Without a high end scanner like a Tech 2 or Snap-On or a means to view live data from the two TPS's and the throttle body, there is no way to verify the actual performance of the system. One check he could do is continuity of each wire from the pedal sensor and throttle body to the PCM and grounds according to the posted schematic by @TJBaker57 . Could also check the 5v reference voltages. Without actual sensor data to confirm, next would be to pull out the parts shotgun again and replace the pedal sensor since the error code points to that end of the system and the throttle body has already been replaced.

 

[budwich]

OP, you might provide a bit more history about the problem... ie. why was the throttle body changed out? What was the previous problem? Perhaps the previous problem is still an issue and basically the "root cause" has not been addressed by changing out the throttle body. The likely place to look is the 5v AND its association with the fan clutch which has a tendency to cause issues to the 5v supply which then "hinders" the throttle body / throttle position sensor stuff. Hence, if the fan clutch is the root cause, changing the throttle body would likely not be a solution.

 

[TJBaker57]

Without a high end scanner like a Tech 2 or Snap-On or a means to view live data from the two TPS's and the throttle body,

Just a reminder,,, all these sensor data are viewable with an OBD2 adapter and an app like Torque Pro. Yes there is some user setup required but it will get you a look at the data for under $20.

More PIDs for Torque App

A short time ago I posted a new pid I discovered for the Fan Speed of a 4.2 in a 2002 Trailblazer. It was properly suggested by MRRSM that I repost that information here so here I am. It is possible that this is my first original post! I have been spending a great deal of time fiddling with...

gmtnation.com

 

[Mooseman]

The likely place to look is the 5v AND its association with the fan clutch which has a tendency to cause issues to the 5v supply which then "hinders" the throttle body / throttle position sensor stuff.

Forgot about that too. Definitely worth a look. To test that, just unplug the fan connector and take a short drive.

 

[mrrsm]

A location where the EV Fan Clutch Shorts Out due to Friction Wearing into the Insulation: