Cedarberry

Just got my car outta the body shop gettin flared fenders installed, took a 1/2 hr ride to store, when I came back out and started car to leave I have the fault.

Is there some way to bypass the fault for now till I have time to troubleshoot it.

New tires are 1 inch in height diff, seems that should be ok.

Tried restarting the car and also hittin the reset on DIC, also I hit the traction control button and nothin would reset it

I'm going to look under the rear of the car and such, see if I notice something broken, any help would be great. I'll post the codes in awhile, had to come home to get the directions for pullin codes

Thanks

Cedarberry

Pcm p1120 h c
p1221 h

tcs c1255 h
c1278 h c

bcm b2721 h

ldcm b2262 h
b2264 h
u1064 h

rbcm b2263 h
b2265 h
u1064 h

rfa u1096 h
u1016 h
c2120 h

Cedarberry

Also while checking the codes, none will reset.

Car has a hard traction control, reduced pwr fault, the service traction control/reduced engine pwr message resets, then within a few secs comes up again. Will not rev past 2k rpm, had to drive home at 40 mph, lol.

Imagine the ecm totally crapped out.

I went through all the grounds last year on it, preventative maintenance thing.

Cedarberry

Been goin thru the factory manuals, the PCM faults are related to the TP sensor, seems they will give you reduced engine pwr message.

Can't find the codes for the TCS faults, still looking

Cedarberry

TCS faults are
C1255 EBTCM internal malfunction, CEBCM internal malfunction

C1278 TCS inhibited by PCM

Cedarberry

Any help in where to start, or just start looking for a ECM.....

All these ecm ebcm bcm pcm's have me all messed up,lol. Factory manual is a real pain navigating between the volumes, goin here and there, what a cluster...., GM needs to check out a military TO.

Cedarberry

So after reading the service manuals, it says that the TP sensor( throttle position) will throw the traction control/reduced engine pwr message, as well as causing other codes when it fails.

Then it also says the TCS malfunctions I'm getting can also throw other codes when it fails.

Not sure what the RFA module is yet.

I'm thinking that the TCS codes, being sent from the PCM, caused those failures. Meaning, the c1255 (EBTCM) a internal malfunction was caused by the c1278 (TCS inhibited by PCM)

The p1120(TP sensor 1 circuit) p1221 (TP sensor 1-2 circuit) caused by the failed TP sensor which inhibited the traction control.
That's my thinking. Will look for the TP sensor and check voltages there.

Cedarberry

Then again if I'm unable to reset any of the codes, then the ECM is bad, no?

Then again when the serviceTC/ reduced engine pwr is displayed I'm able to reset that to the odometer and enter the DTC, so im confused.

Have been learning a few things about how this car works though, sensors up the wahzoo

BigGun

Deal with the throttle position sensor issue first. Especially check the wiring and connecters when you are checking voltages, a known problem area. Fixing that should get you out of reduced power and you can see what else is going on. Your pcm is most likely fine. Not likely given the codes but make sure your battery is fully charged. After sitting in a shop it may be low which will cause numerous problems.

dadaroo

I would disconnect the battery for a few minutes to reboot everything. At the same time make sure the battery is at least 12.5 or higher. Measure the voltage AT the battery.

PS: Sometimes I have problems locating a DTC code. If you look at the index at the very back of the FSM it will list the DTC codes and tell you which section and page where they are located. Saves a lot of time. Just had to do that this morning.


Mr. Sam

Cedarberry

Thanks guys, gonna head down to the shop here in a bit and I'll try disconnecting the battery and hopefully it resets.

I'll putt it home and go from there, we're is the TP sensor located, thanks

Cedarberry

Mornin Sam, I haven't forgotten your help with gettin pass side wired for pwr seat, I'll get with ya when seats get here.

Thanks for the info, much appreciated

dadaroo

Here are the P1120 and 1221 diagnostics. Also the TP and APP schematics.

Let me know if you need anything else.

https://www.dropbox.com/sh/s5dptdsrp...kY2u5vU9a?dl=0


Mr. Sam

Bill Curlee

Thanks for Serving Brother! I agree,, the Factory Service manuals are difficult to get use to but,,, Once you know how to navigate through them, there a GOD SEND!

That being said,, You MUST eliminate POWER as the root cause of your issue FIRST!

Remove the battery, fully charge it. Take it to a shop or store that can FULLY test it. Check for Cold Cranking Amps, & Reserve Capacity. Also look at the voltage available when the battery is under LOAD. If its LOW, thats an issue..

I hate listing a bunch of stuff to check without gathering some facts first so,, get the battery out of the way first. Please report the data on the battery test and we will go from there. IF,, the battery is marginal, I recommend replacing it.

Bill

Vanover

I'm with bill all those issues at the same time, it the batt.

Cedarberry

Bill and 8 vette7, thanks for checking in.

Just got back from the shop, first thing I did was disconnect battery for a few mins and reconnected. It did reset but faults came back in seconds.

Read voltage across the batt, 12.4 volts. Put a charger on it for a bit got to 12.9v and turned key on and got the pull key wait ten seconds and the previous faults. Still unable to clear codes.
Checked for a batt drain and that's good not pullin amps.

Buddy had a gizmo that plugged in under the steering g wheel and was able to read codes and he was also able to clear them while car was running. Hit the throttle and it revved normal and then within a few secs the idle dropped below 1k and the idle was rough, nearly shutting down. Would t even rev to 2k anymore.

The pull key wait ten sec was gone.
So I put it on battery tender for now, will check it out tonite as the tender was flashing red and before I left it was green.

I have a yellow top optimum batt that had purchased 2 yrs ago, always on a batt tender when not driven. Which does not mean it's not bad. Body guy says the yellow top is a deep cycle batt, and the red top is what should be in there.

Anyway the car has been in the shop for a month, with rear deck, doors and such opened lot, they even had to charge it one time to move it, so I'm lettin it charge up good and I'll go back and check it out tonite, and tomorrow take it to a auto parts place here and have it checked.

While charging it I crawled under the rear to make sure nothin rubbin on the new tires and visually looked around the throttle body. It's Sunday and body guy had other stuff to take care of, so I'll go back tonite and see if a good charge fixes the problems.

It just baffles me, that I drove it for over 20 mins with no traction control problems, which seems like it should have charged the batt good.

Also when I disconnected the batt to reset the whole works, and still have the TCS faults, you could rule out the tire size causing the malfunction. I did get a straight edge and measured the tire height, have a inch and a quarter to inch and ahalf diff in tire height, right at the edge, no?

So I'll have more info tonite
Thanks again guys, much appreciated

Cedarberry

Hey guys, I'm at the shop thisorming, car sat on trickle charger all night, fired right up, ran and revved up no problems, not throwing the Pcs codes for the TPS sensor.

Took it for a short ride. Was turning on to the highway and ran it through 1st and 2cd and between shifts the rear tires broke loose a bit and immediately tree the traction control codes and went into limp mode. Only rev to 2k.back at the shop cleared codes with the plug in reader as the dash controls wouldn't reset it?

While I took the test drive, I pulled over and checked codes, all were H now, but none would reset for me using the dash reset button.

Here are my tire sizes
Front 275/30zr19
Rear 345/25zr20

Cedarberry

Runs and drives great now, only thing worrying me is that the dash reset button will not clear the codes, and a bit of tire spin with traction control on, the car threw up the TC faults and would not reset with out the external reader.

Cedarberry

What do you guys think?

Cedarberry

Crap, just fired it up again and back to square one, right were it was.

I'm at a total loss as to wth is goin on.