just so everybody knows the fix for chad b's problem is the pcm i had the same thing happen on mine and after a year long battle with my truck i found a re manufactured one on ebay for i believe $120 by a seller called flashmasters.
its not battery terminals or any other crap that people were saying in the last post sorry for the delay chad i hope somehow this post finds you since somebody locked the last one.
by the way this is a very dangerous problem these truck will shut off randomly i'm surprised know body been killed yet by this, the engine light comes on but it doesn't give a code that helps figure out whats wrong

 

You mean that every time Service Stab Sys, Traction Failed, Reduced Power appears in the DIC it is always just the PCM?


.... and you have reached that conclusion without even knowing what the code was that his truck stored.

Was the code(s) you had the same as Chads?


Well that rules out the other 30 - 40 possibilities rather quickly. Thank you so much.

 

when your driving down the highway and that message comes on as the truck just shuts off when your doing 80 in traffic and your looking for a place to coast out of the way so you dont get run over. and once you get stopped and put it park and wait about a min and the truck starts right up again. yeah thats it. but the crazy part is it does not give a code that leads to your pcm. just a stab sys code if i remember correctly. it drove me crazy for a year before i figured it out.

 

Wow, that is one he'll of a blanket statement.

When mine did it 3 different codes showed up. Ended up being the accelerator pedal position sensor. Replaced the entire pedal assembly and whalaa no more codes nor reduced power/traction control failure etc.

It's not always the same cause that sets off that message. You have to read the codes from the OBD II port under the driver side dash. Most auto parts stores will read them for us if you don't have one. Figure out what each code represents and go from there.

 

Just got the same with my 2008 Alpha: Running offroad (nothing too major, mostly fire roads with some decent ruts and ledges) in 4HI LOCK for about 2 hours. Suddenly got the SERVICE STAB SYS -- TRACTION FAILED -- REDUCED POWER message on the dash, along with the CEL and Stabilitrac light. Luckily, was already past the tougher sections and had only smooth dirt roads left; nursed it home, checked the codes; P0452 Evap Pressure Sensor, P0641 Sensor Reference Voltage A Open, P0106 Manifold Absolute Pressure. Clearing the codes doesn't change anything, it immediately throws them again when you start it up.

So then I tried pulling a few fuses (BCM, TCM, PCM) for a few minutes and reinstalling them, and pulled the battery negative cable too. Wouldn't even start; just cranks. Cleared the codes again, and it started, but ran very rough, misfiring, and then died. Now it will sometimes start, most times not start. When it does start, it bucks and misses, then often dies and won't restart. Clearing the codes seems to allow it to start again, but immediately acts up and throws codes again. WTF?

Another strange thing; sometimes when you try to start it, it keeps cranking even after you release the key back into the run position. I have to turn the key back to ACC for the starter to stop cranking.

Still under the limited warranty from the dealer I bought it from just 2 weeks ago; they want me to tow it to their shop on Monday. Keeping my fingers crossed that it's not something major since the warranty only covers 50% of parts & labor.

BTW, I know this was a thread from January, but I wasn't sure whether to bump or start my own. Seems if someone starts a new thread here, shouts of "use the search feature" come up, but if they bump an older thread, shouts of "this is an old thread, start your own" come up. If I'm wrong here, just let me know and I'll delete this and start a new one instead. Thanks.

 

OK, update. I went out this morning and the truck started right up, smooth idle, no messages in the DIC on the dash. Still had the CEL but no Stabilitrac light. Drove it up the street and back and seemed to run perfect. So I plugged in my scan tool again: Same codes again: P0106-Manifold Absolute Pressure/Barometric Pressure/Circuit Range/Performance, P0452-Evaporative Emission System Pressure Sensor/Switch Low, P0641-Sensor Reference Voltage A Circuit Open. However, this time when I cleared the codes, they stayed cleared. Drove it around the block a few times, switched from 4HI to 4HI Lock and back, turned the Stabiltrac off and on... Running perfect, no codes, no CEL, no error messages. What the H is going on? Still gonna take it in to the shop on Monday for a once over, but not confident that anything will be found now. At least I don't have to tow it in.

 

Nope, spoke too soon. It's now back to the same problems. What the H3LL is going on?

 

po641 & po452-->Fuel Tank Pressure (FTP) Sensor Wiring.

Locate the Fuel Pump Control Module (FPCM).

2. Inspect the module and connector for corrosion.

3. Check power and ground to the Fuel Pump Control Module (FPCM).



DTC P0641
Circuit Description

The powertrain control module (PCM) provides a 5-volt reference to the following sensors:

The throttle position (TP) sensor 1
The accelerator pedal position (APP) sensor 2
The AC pressure sensor
The fuel tank pressure (FTP) sensor


The PCM monitors voltage on the 5-volt reference circuit. If the voltage is higher or lower than required, DTC P0641 will set.

DTC Descriptor

This diagnostic procedure supports the following DTC:

DTC P0641 5-Volt Reference 1 Circuit

Conditions for Running the DTC

DTCs P0601, P0602, P0603, P0604, P0605, P0606, P0607, P0621, P0622, P1621, P1680, P1681, P2610 are not set.
The ignition is in the Unlock/Accessory, Run, or Crank position.
DTC P0641 runs continuously once the above conditions are met.

Conditions for Setting the DTC

The PCM detects a voltage that is higher or lower than required on the 5-volt reference circuit.
The above condition is present for 1 second.

Action Taken When the DTC Sets

The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.
Conditions for Clearing the MIL/DTC

The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

1. Disconnect the following, while watching the 5 V reference to the FTP sensor: Air Injection Reaction (AIR) pressure sensor, part of the AIR switching valve, Throttle Position Sensor (TPS), located within and part of the Throttle Actuator Control (TAC) motor, A/C pressure sensor, Accelerator Pedal Position (APP) sensor, part of the gas pedal assembly.

2. Replace any of the above items that caused the 5 V reference to drop low.

3. If above does not bring the 5 V reference back, check the Gray, Tan or Brown/White wires leading to each of these components for a short to ground.


GL

 

Thanks for the info, Hummerz. I'll give this to the mechanic when the truck gets dropped off (not that he shouldn't already have it, but...). What adds to the puzzle when the messages/reduced power is present, is the Traction System/Stabilitrac is also affected, and the starter motor operation is wacko (i.e. it takes a second to actually start cranking when you turn the key and continues to crank for a 3-4 seconds after releasing the key), and the A/C compressor doesn't engage (blows hot air), and occasionally even the word OIL shows up on the DIC. All of these random, seemingly unrelated systems.

 

Got a call from the shop yesterday afternoon; here are the results. #1 the mechanic was able to trace down and find a broken wire at a connector under the hood (sorry, I don’t know which wire or any other details yet; I’ll try to get more when I actually talk to him in person). He fixed that (replaced a connector). #2 the reduced power mode was triggered by the TPS in the throttle body malfunctioning. Turns out that GM has issued a TSB for that part and will cover the repair of it through 10yrs/120,000 miles (NHTSA #10047220, TSB 11273). The mechanic is taking it to the Chevy dealer today for the covered repair/replacement.

Bottom line, the used car dealership where I bought it stepped up to the plate and covered the shop/mechanic 100% (even though they could have charged me 50%) and Chevy is covering the TPS replacement. My cost: $0.