1994 K1500 stalls only when brakes applied

[FM9694]

Outstanding! Sincerely appreciate your continued status updates. FWIW here's an interesting
illustration of the wiring harness to the internal transmission solenoids for those reading
this thread and trying to picture the physical implementation of this circuit path:

You must be registered for see images attach

Looking forward to you getting a good new harness installed and solving this
difficult stalling symptom.

Nice job staying with it. (!)

Just to get your opinion as well, to confirm this I followed your steps of depin black / tan wire from PCM and tested with truck on and got 0v. I then turned truck off and tested the tested the now free black / tans wire resistance to ground which it showed continuity, thus diagnosing uncontrolled grounding of this wire. When transmission harness was unplugged, continuity was gone, demonstrating that the uncontrolled ground was somewhere from trans connector to the solenoid itself. New harness on the way and thank you so much again for your help. Will update to confirm fix

 

[94k1500gm]

desperately need some help here.

Situation: 1994 K1500 stalls only when brakes are applied. I originally thought it was when it was put in gear, but it’s only when brakes are applied that it stalls out.

Work done so far:

New Distributor, cap and rotor
New plug and wires
New coolant temp sens
New IAC
New TPS
New O2 sensor
New EGR
New TCC solenoid
New torque converter
New map sensor

Truck starts back up immediately after stalling and idles fine

I would unplug the brake light/cruise control switch on brake pedal and reapply brake

 

[mwilliams55555]

The problem is that the truck stalls "only" when the brake is applied. Not when put into gear.

If the TCC was the problem, the truck would stall any time the vehicle was in-gear, and the speed got low enough--brakes applied, or not applied.

As described so far, this is not a TCC problem. It is "probably" a vacuum-booster problem.

I had a 84 that did it,new booster solved it on mine

 

[FM9694]

Outstanding! Sincerely appreciate your continued status updates. FWIW here's an interesting
illustration of the wiring harness to the internal transmission solenoids for those reading
this thread and trying to picture the physical implementation of this circuit path:

You must be registered for see images attach

Looking forward to you getting a good new harness installed and solving this
difficult stalling symptom.

Nice job staying with it. (!)

No luck man. Got the new internal wiring harness and installed it. Plugged in the external connector and the continuity is still there. Unplug the connector and it’s gone. Now I do not know where the short is. Could it be the external (plug in) portion of the connector? I really cannot understand I tnoghit I had it down

 

[chris032188]

Im in South NJ - i have a scanner if you think you might need to use it LMK

 

[FM9694]

Im in South NJ - i have a scanner if you think you might need to use it LMK

A scanner to find the short ? I’m in central NJ near flemington

 

[someotherguy]

No luck man. Got the new internal wiring harness and installed it. Plugged in the external connector and the continuity is still there. Unplug the connector and it’s gone. Now I do not know where the short is. Could it be the external (plug in) portion of the connector? I really cannot understand I tnoghit I had it down

Are you sure about this short? I haven't been following closely so I just skimmed the thread; when I saw the title I was ready to jump in with brake booster failure and I see Schurkey already mentioned it.

If the TCC was locked when it should be unlocked, causing the stall then it would do it regardless of brake applied.

Stalls only when brake applied tells me it's more likely a massive vacuum leak in the brake booster. Have you tested by removing, and capping, the vacuum line to the brake booster? Only do this in an empty area like a vacant parking lot. You'll have no brake assist so the brakes will be hard to apply. But with the vacuum source removed, and the -engine- side capped so it's not leaking, it doesn't stall with brake applied = booster is bad.

Richard

 

[FM9694]

Are you sure about this short? I haven't been following closely so I just skimmed the thread; when I saw the title I was ready to jump in with brake booster failure and I see Schurkey already mentioned it.

If the TCC was locked when it should be unlocked, causing the stall then it would do it regardless of brake applied.

Stalls only when brake applied tells me it's more likely a massive vacuum leak in the brake booster. Have you tested by removing, and capping, the vacuum line to the brake booster? Only do this in an empty area like a vacant parking lot. You'll have no brake assist so the brakes will be hard to apply. But with the vacuum source removed, and the -engine- side capped so it's not leaking, it doesn't stall with brake applied = booster is bad.

Richard

Yes the booster has been ruled out with the check

 

[JDGMC]

Yes the booster has been ruled out with the check

You’re not going to solve the problem unless you rule out the other factors that can cause this. Many questions about the history, settings and run condition of the vehicle have not been addressed. Take it to a mechanic.

 

[Jimmy D]

I may have missed it but what is the warmed up idle speed? Have you sprayed something like starting fluid around the base of the throttle body and intake gaskets looking for vacuum leaks? It could be as simple as idle speed setting too low. My bone stock '91 routinely stalled while in gear with brake applied. I raised the idle speed a bit and took care of that.