Triple threat, time to ask

[Striker-7]

Thanks be to you stubborn rascals, I appreciate the information presented here and at the OS.

What I've got is an irritating occasional Check Engine / Stabilitrak warning that drives me nuts, along with 'killing' my A/C door mode actuator with a battery change. I think I've got a lock on the actuator issue (RockAuto ACDELCO Part # 1573596 and 30 minutes with assorted tools), but the first problem has me puzzled as to what I actually need.

I use a ScanGaugeII to watch over the vehicle, bolstered by Torque Pro and a PLX Bluetooth OBD2 interface, plus a read of the long-term by Autozone when it became more than occasional. The codes can be cleared and I can drive the TB for a couple hundred miles with no re-occurrence, *as long as I don't slow drive in a parking lot*. Within a couple minutes of either being stuck in traffic at stoplights, or slow creeping in a parking lot, the CEL comes on. Torque invariably shows a P0121, "Throttle position sensor circuit A fault", but rechecking with the ScangaugeII gives B2AAA, a bogus ID that the Autozone code reader claimed was "Steering angle sensor error". Wonderful. Knowing how interrelated all this can get, I sense that those might be triggering the very intermittent "Service Stabilitrak" warnings I get on wet days, again in very slow driving conditions.

So, the questions:

P0121 refers to the gas pedal position sensor/sender, or the sensor on the throttle body itself?

B2AAA (unknown true code) "steering wheel position sensor error", is this a common fault?

Did Han shoot first? (scratch that...)


Thanks for reading. RockAuto order on hold until I sort this out.

 

[Wooluf1952]

Welcome

In case you haven't heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/

If you fill in the info about your truck it will help.
Year, what you're driving, I6 or V8, maintenance history, etc.

 

[Denali n DOO]

Welcome to GMTNation!

I had the stabilitrak light going on usually when backing out of the driveway or slower parking lot driving. The code mine set was P0455 and they said the steering post sensor was faulting. It was called Sensor SP, GM #19150081. The dealer price was $296.64 for the sensor...

 

[Striker-7]

Welcome

In case you haven't heard:
http://gmtnation.com/f5/welcome-gmtnation-com-heres-story-226/

If you fill in the info about your truck it will help.
Year, what you're driving, I6 or V8, maintenance history, etc.

I could've sworn that stuck (on the sidebar, the personal stats)...

2007 Chevy Trailblazer LT, 5.3L V-8 2WD w/M30 automatic transmission. Interior is the "power everything" option, including the Driver Information Center, auto cabin temp control, 8-way leather seats, Bose XM radio, you get the drift. First time you unknowingly turn on the seat heat in summer, well, that is a unique sensation.

Purchased used w/ 55,000 miles, now turned 83,000, routine oil changes via the DIC "Oil Life" as per the manual. It's been drinking engine oil like the proverbial sailor on shore leave (quart every gas fill, worst I saw was ~375 mile / qt). I think I've got that turned around via an old trick my dad knew of, the last check / top off was ~1400 mile, but other than that and the reasons for the thread, it's been pretty stout.

As to maintenance before I got the beast, it appeared from the CarFax and VIN sheet on TV that it was a fleet vehicle, and judging from signs around the vehicle, I'd say middle executive with at least one toddler, heavy commuter, with an inability to judge corner location when parallel parking. No, despite the trite saying, "It don't just buff right out".

 

[The_Roadie]

P0121 and codes that use the phrase "throttle position" have to do with the throttle body. GM calls the other thing the "APP sensor" usually for "Accelerator Pedal Position".

 

[Striker-7]

P0121 and codes that use the phrase "throttle position" have to do with the throttle body. GM calls the other thing the "APP sensor" usually for "Accelerator Pedal Position".

And to twist the dagger just a smidge, the code today is an unambiguous P0121 on the ScanGauge II . Thanks for the clarification, TR.

Ordered the SWAS and air door actuator this morning, figured I'll try cleaning the throttle body, clean and reseat the throttle body / APP connectors before replacing that chunk of hardware. As far as doing the R&R on the steering wheel angle sensor, if I can handle rigging flight controls on a KC-135 Stratotanker's refueling boom, dealing with one rigging pin in a steering column can't be that bad.

I'll update results when I get going on the repairs.

DenaliNDoo, thanks for the tip!

 

[Wooluf1952]

The oil consumption is a known problem. IIRC, it's a problem with one of the valve covers.

 

[Striker-7]

The valve cover is part of it, but the problem is the Active Cylinder Management system getting the engine in a condition where it pulls oil past the valve guides / piston rings in the shut-down cylinders. GM has a detailed "recovery / repair" document which depends mostly on Seafoaming the cylinders first, then the engine rebuild.

Dad's trick is changing oil brands / formulations each time the engine comes due for oil change. While the oil weight stays the same, each manufacturer has a different additive package. Switching things up can break down and flush deposits that using one brand religiously can build up. I have no idea what was in the vehicle when I bought it, the "oil suck" had already started, so I went with Dad's plan to see if I could turn it around without having to deal with the "stealership" in this area (GM Giant, who went under in a glorious gale of cocaine rumored insolvency).

I used Castrol GTX 5W30 to top off until the DIC called 5% remaining life.

First change was GTX again for routine maintenance, noticed the burn rate was getting alarming.

Next change, complete formula swapout. Valvoline Full Synthetic. Burn rate went in the toilet; there was one documented point where I ran a quart every 300 miles. The rate slowly dropped off during the DIC life cycle, but was nowhere near what I'd call "normal".

Latest change was back to Castrol, but their 5W30 dino-synthetic mix. Too early to tell if the "fix is in", but a 1320 mile interval from first fill under the usual driving cycle looks promising.

 

[Striker-7]

Replaced A/C mode door actuator per instructions here and at TV. Took about an hour, and two attempts at sync'ing the gear set, some minor snarling at the actuator while trying to get the white sector gear to sit on the case boss, but successful in the end.

I found I should not depend on the door gear to hold any position, since gravity drops it towards one limit and the new actuator comes in a middle spot. I installed the new one, thought I had it aligned, ran the "fuse reset" sequence and watched the actuator cycle through. Testing showed I missed the alignment, and pretty badly at that, since the gear shaft was visibly straining. Pulled the actuator back off, did NOT reset via the fuse pull, turned on vehicle power and selected the "dash vent" position to let the loose actuator swing to its learned drive limit stop, and killed the ignition. I put the actuator back into the seated position, but before fully engaging it on the case, reached behind and pushed the door gear to its CCW (counter-clockwise) stop point, then meshed the white sector gear to it by seating the actuator. Tightened down the screws (7/32nd short and deep 1/4" sockets work great in the confined space), did the HVAC B fuse reset again, and was rewarded with full airflow where selected.

Winter ready, at least inside! :wootwoot:

 

[Striker-7]

Two thousand miles later...

The air door worked flawlessly during the road trip to Georgia and back for a play date with NASA Southeast. Full auto takes some getting used to.

Oil mileage is still a bit wonky, now about 500 miles per quart average, but under the circumstances of the trip it could be partially excused (4500 lb trailer, third gear high-throttle pulls uphill, 70+mph Interstate drone).

No repeat of the P0121 / B2AAA codes. None. All I did was clean every item (when possible) and its associated electrical connector. MAF sensor, throttle body and accelerator pedal. Long idle periods, parking lot creep, not a flicker from the CEL.

 

[BRomanJr]

Two thousand miles later...

The air door worked flawlessly during the road trip to Georgia and back for a play date with NASA Southeast. Full auto takes some getting used to.

Oil mileage is still a bit wonky, now about 500 miles per quart average, but under the circumstances of the trip it could be partially excused (4500 lb trailer, third gear high-throttle pulls uphill, 70+mph Interstate drone).

No repeat of the P0121 / B2AAA codes. None. All I did was clean every item (when possible) and its associated electrical connector. MAF sensor, throttle body and accelerator pedal. Long idle periods, parking lot creep, not a flicker from the CEL.

Great news on the Actuator fix.
Have you replaced the Driver side Valve Cover yet? (only buy new GM part) That and some spirited driving or top engine cleaner to "clean" the rings should cure most of it.

I went from less than 1000 miles per quart to over 3,000 per quart by doing the above.
Obviously I don't have DOD (AFM in later years) so my results are not based on oil consumption problems with that system.