About a month or so after I installed that Viper alarm, I started to notice a really rough idle. When I come to a stop, the idle will drop rpms very low and the voltage readout on my gauge shows a drop to as low as 12.- volts. The car has since worsened and began to show REDUCED ENG PWR on the DIC just about every time I start the car. Roughly 5-8 seconds after startup. The combination of codes vary between the 3 I listed in the title. The most common being P2135 and P1681. The P0520 has only displayed once IIRC.

Today I Performed a rough uninstall of the alarm, thinking this was the problem, and I was wrong. I removed the GM override XK06 box and the remote start satellite relay. I also removed the in-line fuses for the viper brain as well as the ground connections to ensure that everything Viper was bypassed. I am still facing the same idle issues as well as the engine performace being reduced. Initial thought was a A bad ground somewhere, but no luck on finding anything resembling that. What are the odds of the PCM going bad out out of the clear blue?

Any thoughts here guys?

 

P1681 means you need a PCM. Thats easy.
P2135 could be setting falsely, or it could be a TB or wiring issue.

 

Yeah, I remember finding that out about 1681. I would just hate replacing it and have that not be the problem. Any idea if this could be a reason for the idle surging? Also, is there a way to transfer my already purchased credits for Hp tuners to another PCM so I can avoid spending more money?

 

reduce engine power is coming up on mine too. i called onstar techs and they said im not getting any fuel to my fuel rail do to low voltage on the fuel pressure regulator solenoide 1. any idea where that is.... its prolly unplugged

 

Well my morning today was terrible with the addition of P2101 on the interceptors. I'm going to pull off the intake at the throttle body and inspect for anything out of the ordinary after work. The car felt like it was going to blow up initially.

Yeah, I'll take a look.

Well I pulled the intake to take a look at the TB and everything here looks good to me. Anyone see anything odd?

 

P1681 is an internal module failure. the ONLY repair I know of is replacement.

 

Has anyone here had any combination of these codes, changed the PCM, and had no further problems?

The reason I ask is because it's gonna cost me $100 to tune the new PCM with the new credits I will require with HP Tuners.

 

the engine power reduced happened to my brother's car last month when i was driving it. took it to autozone and they said it was bc of the throttle positioning sensor. could be that as well?

 

I got a 2135 on the way home today, twice. It went into reduced engine power and was chugging along. Luckily I had the interceptor and I cleared the code.

That is all I had though, the 2135. I guess I could be the PCM, or the used LSJ TB I got. There is a bulletin out about wires rubbing on the evap solenoid bracket, but my wires are in the tubing and there is no rubbing.

 

THE BALT IS BACK!!! Changed out the throttle body with a spare and this puppy runs like the day I bought it. No more idle surging and the jerking forward when I left off the gas pedal while coming to a stop. I just took the car for a spin and beat the **** out of it. Handled the abuse like it should and still came back in idling smooth.

 

That is good to hear. I just got a new TB today and I will install it tonight. Hopefully that is my reduced engine power issues!

 

I have this same problem it makes me made i dont now were to start. I get it when i go wot if i just take it slow it wont mess up and sometimes it happens when I start the car. I get p1516 and p2135. im getting pissed off.

 

Hey guys, these are the same symptoms I'm having. I'm having a variety of codes:
P0069 - Manifold absolute pressure - Barometric Pressure correlation
P0135 - Oxygen Sensor Heater Circuit Malfunction (Bank 1 Sensor 1) - see our "articles" link for additional help with these generic check engine light codes
P1516 - Throttle actuator control (TAC) module throttle actuator position performance
P1681 - Powertrain Control Module Fault
P2101 - Control Module Throttle Actuator Position Performance
P2135 - Throttle Position (TP) Sensor 1-2 Correlation
P2229 - BARO sensor circuit high input

All this started happening after a tranny swap that took quite awhile.. the PCM was laying on the bench for a month or so without power...

Could this have caused these issues? Problem with swapping the PCM is I no longer have HPTuners to put the OTTP stage 2 tune back on it.. :-/