tcc lock up LED

[lupey6.5]

could someone tell me the procedure for installing a tcc lock-up LED indicator

[lupey6.5]

come on i know you know that i know that you know how to do this

[jeffreydmet]

I can tell you how I did it on my 99 K3500.

I found an ingnition switched hot wire under the dash on the connector block. I run this to a LED then through a 500 ohm resistor then to a scotch lock to the Brown wire on the Blue connector on the back of the PCM. If the polarity on the LED is backwards it will not light. You can test the polarity by hooking the LED resistor combination up directly to the battery. The PCM drives the TCC Solenoid by grounding the Brown wire.

[Scooby]

Jeff, what is the purposre of the resistor in the circuit ??

[MikeC]

Jeff,

If grounding the wire is what locks the TCC, what would prevent a switched ground from working on this to manually lock it??

Codes?

Other issues?

Mike

[gmctd]

The 4l80E TCC is not simply grounded thru that PCM pin - it is grounded approx 30 times per sec.

TCC off is very narrow 30hz pulses, TCC on is very wide 30hz pulses.

Pulse width is modulated according to engine demand.

Hard ground the pin, buy a transmission.

I would not put any device on that pin, but as you have done so, you might put a 10ma fuse in the LED ckt, in case of short ckt condition.

Or buy a PCM.

Caveat emptor, dudes!

[ 12-06-2003, 07:30 PM: Message edited by: gmctd ]

[MikeC]

gmctd,

If a PCM is reprogrammed, is TCC lockup one of the parameters that can be changed from stock?

I understand the PCM runs my truck but I don't really understand all it controls VS another box in the truck contolling things also.

Mike

[gmctd]

Mike, if you have not already, you might check out ronniejoe's BD Torqueloc article currently in the Member's Area for some additional info.

If you were to have your PCM (Powertrain Control Module - engine AND transmission management) re-flashed to '99 high output specs, the transmission functions should also be upgraded to handle increased engine hp\torque.

Don't know what the aftermarket PCM re-flash does, but I think most aftermarket 'boxes' manipulate the 4L80E input speed sensor vs output speed sensor ratios for shifting and TCC management.

I am still earnestly seeking that Rosetta-stone of PCM Revelation, the TECH-II, because I truly dislike having to semi-educatedly out-guess these things.

[MikeC]

gmctd,

Thanks for the reference. The note at the bottom of the article advises what several here had already told me, that being there are issues with it and the OBDII systems.

My Burban is a 96 with OBDII :(

A reprogrammed PCM is in the thought process now and the TCC and Trans controlling is going to be questions asked.

Thanks,

Mike

[jeffreydmet]

Scooby

The resitor in the circuit limits the current through the LED. An LED is not like a light bulb that has its own resistance which limits the current. An LED is more like a regular diode that passes current freely in one direction but not the other.

I am not an expert on this truck but have a Mechanical engineering background along with some significant experience in controls engineering. I also have studied the helm manuals a lot.

It appears GM has done a good job of trying to protect the PCM. There are error codes on almost all of the circuits such as the TCC that throw a code if the circuit becomes shorted to 12v or to ground. If a short to ground or 12v toasted the PCM the error codes would be pointless. This should make it hard to tear up. However here lies the problem of simply switching the TCC solenoid to ground. The computer is monitoring the health of that circuit. If it becomes grounded or shorted to 12v it will throw a code and possibly go into limp mode.

Another thing I always worry about when switching solenoids is the very large voltage spike that occurs when a solenoid is switched off. Voltage spikes can be devastating to electronics. There are ways to take care of this but one has to be careful.

Another thing the computer is looking for is that the TCC is not stuck on when it is not supposed to be. It is looking for appropriate slip in the TC under certain conditions. I'm not sure how to fool the computer about this. However the stuck on error according to the manual turns on the SES light, commands max line pressure and freezes shift adapts. Not necessarily a big deal. This still might be a preferable way to run up long steep hills in 2nd without overheating.

If I am wrong on any of this please let me know I'm always willing to learn something new.

[gmctd]

In re-reading my post, it seems rather severe.
My apologies, as no aspersions were meant.

The PCM monitors most driven circuits for a high, indicating continuity thru the solenoid to power, and a low, indicating lack of continuity, or open.

It wants to see the high when off, and the low when on.

A low when off sets an alarm for error in solenoid or wiring, a high when on sets a control alarm for error in PCM - open driver and such.

But, the PCM has no method of checking or compensating when added circuitry fault occurs.

The open collector drivers may be damaged if a short to +12v exists, which case would ensure a really open collector upon command to switch on.

A short to power is catastrophic where a load impedance to power is expected.

[rjschoolcraft]

After installing the BD TorqLoc in my 95 Suburban, I stumbled onto the fact that the PCM sets code 69 "TCC Stuck On". This does not turn on the MIL and will clear after one ignition switch cycle with the condition gone. I have found no other anomalies with this installation.

I spoke with a BD rep at the SEMA Show 2003 and they were unaware of this situation. Furthermore, they still insist that they have many successful OBDII installations and state that HowieE's problems are installation related. I know that Howie will dispute that claim. They also said that "he probably didn't bring it to our shop" so they could fix it. However, I know that Howie has said he took it there twice.

I was a bit disappointed that they were completely surprised by the code 69 issue. Since it doesn't cause any drivability problems, though, I'm no too worried about it.

[jeffreydmet]

gmctd
It takes a lot for me to be insulted or ticked off, after all I have a teenage daughter to live with.

But seriously though, the helm manual on the TCC circuit list an error code for the circuit being shorted to ground or shorted to voltage. I would not think they would bother with the codes if it trashed the PCM. For these codes to do anything I would think circuitry has to be built in to allow for these conditions. Also some of the diagnostic charts involving shorts call for the short to be repaired then it should be ok.
What am I missing?

[gmctd]

Might be easier, Jeffrey, if you could give the specific verbiage you are referring to, so we're on the same page.

DTC-83 TCC PWM solenoid fault is set for
High when Low-expected - short to +12v (solenoid or wiring), replace PCM
Low when High-expected - blown fuse, solenoid open or shorted to ground

Supposed to be second OBD-I DTC for this (1995), but not listed.

BTW, do appreciate your input on the FSD/PMD post.
I have that 3"lb torque figure etched in my memory banks, along with BETA's 1/8th turn from contact. Thanks, again.