Yesterday while driving back to my house, 3 high school kids walking home all gave me thumbs up as I approach. Thinking that the gestures were cool (I'm kind of old) I pushed in the clutch and tromped quickly 3 times on the accelerator pedal to acknowledge. Immediately I lost power and the DIC displayed this:

1. REDUCED ENGINE POWER
2. SERVICE TRACTION SYSTEM
3. SERVICE ACTIVE HANDLING

I limped home about 3/4 mile and parked it. I checked the DTC's and these came up initially:

10-PCM P1120 H C
P1221 H C

28-TCS C1278 H

40-BCM B2723 H

58-SDM NO CODES

60-IPC NO CODES

80-RADIO NO CODES

99- HVAC B0338 H

AO-LDCM B2282 H
B2284 H
B2262 H
B2264 H
U1064 H

A1-RDCM B2283 H
B2285 H
U1064 H
U1016 H

A6-SCM B0851 H

BO-RFA U1255 H

So, one by one I cleared all codes shut off the ignition, waited about 5-minutes and restarted the car with the same DIC warnings came up:

1. REDUCED ENGINE POWER
2. SERVICE TRACTION SYSTEM
3. SERVICE ACTIVE HANDLING

And, these DTC's came back on only:

10-PCM
P1120 H C Throttle Position (TP) Sensor 1 Circuit Performance
P1221 H C Throttle Position Sensor 1-2 Correlation

28-TCS
C1278 H Traction Control System Temporarily Inhibited By Powertrain Control Module

Thinking that by me tromping on the accelerator pedal I may have wacked out the TAC (throttle actuator control system) I pulled the air bridge to TB bellows and had my Wife slowly push down on the gas pedal gradually and observed the throttle blade in the TB. It traveled steadily all the way open when the pedal was fully to the floor. She let off the pedal slowly and the throttle blade steadily returned to the closed position.

Before throwing parts at it, can anyone help and advise me on what may be the problem? I did a thorough search here but could not find enough information to lead me in the right direction and process of elimination.

With the TB throttle blade moving with the pedal, is there a "fly-by-wire" accelerator pedal position sensor/switch that could have been traumatized with my tromping the pedal? Or could it be the TAC under the right front fender that has crapped out?

I will surely appreciate your input. Thanks, Joe

 

Update; last night I couldn’t get those 3 DTC’s to permanently clear so I disconnected both battery terminals and waited an hour. After reconnecting the battery, I started the car and there were no DIC Warnings, initially. So as the engine was running I cleared the DTC’s and it was idling fine for about 5 minutes. I was not in the car when suddenly the engine shut off.

I attempted a restart and the same 3 DIC’s warnings came back as well as the same 3 DTC’s

Hoping someone can pipe-in here for me.

 

Most posts with those DTCs point to the throttle position sensor (TPS). I would start with replacing that.

 

Thanks for your input!

I ordered the TPS yesterday from Amazon and they’re $27. A lot cheaper than a TAC Module which you can only buy used or remanned.

I read online that the mid-2000’s Yukon and Envoy’s use the same TAC just that the connectors flip 180 degrees but do plug directly in. The ‘04-05 Cadillac CTS uses the same TAC as the ‘97-04 C5.

William at VetNuts said the Dorman 599-959, which costs $200 at Amazon and O’Reilly’s will work but the TB Motor polarity is reversed so you have to swap around the 2-wires (brown and white pinned wires) on the TB’s motor connector.

Also, PerruzziAutoParts.com sells remans of the latest version ACDelco part 19245405 to fit all C5 for $211+$40 core. Mine is 25311783.

I’ll update later when I try the TPS.

 

Tsumi, you were spot on about the TPS!

Well the new TPS from to remove and replace the old TPS. I rehooked the neg-battery cable and fired up the engine and whalla! It came back to life with no REDUCED ENGINE POWER, SERVICE TRACTION SYSTEM, SERVICE ACTIVE HANDLING or DTC’s at all.

Luckily I didn’t need a TAC because as said above, getting a new one is impossible. The best case is to get a reman and that’s like a 2-4 week wait and the only other alternative is take a chance on a used one for $200-$350. So, it worked out great for me and I’ll surely take a little luck anytime time.

 

Glad I could help and it worked.

 

Out of curiosity, who remanufactures TAC modules?

 

EDIT: Sorry, just realized that this was a C5 thread and NOT a C6 thread.... Oops... Sorry. --------------------------------------------------------------

There is none....In a C6. The ECM has a "Throttle Processor" which is what controls the throttle. It's built into the pcm.

We re-flash the throttle processor with some special stuff here to make the CoW BOOSTER! work.

Chuck CoW

 

Had the famous P1518 code pointing to the TAC. Have service manuals so I copied all relevant pages related to P1518 and the TAC in general. Posts advised that it could be a broken wire at the TAC, TB, PCM, or even the DBW so called PEDAL which has 2 potentiometers one which increases and one which decreases resistance when you step on the accelerator pedal.
Used a DVM/OHMMETER ro check out all leads relating to TAC (TB, TAC, PCM, Throttle Pedal) . All looked good. No broken wires. Spent a bundle to get a TAC. Put it in. Cranked car.
NO START. Had battery (only 5 months old) load tested. It is good. Cranks the hell out of the engine but engine WOULD NOT START.
On advice that it might be the Ignition Switch and NOT the TAC I purchased a NEW OEM Ignition Switch. Used an OBD reader to reset P1518 code and then turned new switch to START.
VOLIA>>> the car STARTED.

You might have a flaky Ignition Switch.

If so skip the procedure to sand down the contacts and GET A NEW SWITCH. It is a D1499C Delco switch. Just need the electrical part not the Cylinder Lock part which includes a VATS sensor. Easily removed with a screwdriver depressed in the SWITCH ON POSITION and then removed.

If you really need a TAC, I have one which ran the car fine but don't really need.
Let me know if you find your TAC is bad.

Good luck and don't get stuck with a dead car miles from home.
BIGHANK