High RPM's at highway speeds, etc.....

[RoRo]

1996 Tahoe 2door 2wd 5.7 190k miles. Don't know if all original or if its been overhauled.

Have a couple of issues that just started today. Drove fine this morning but when it came time to come home I noticed some wierd issues.

First indication was a firm 1-2 shift, did it at low coasting while driving through parking lot, didn't do it at quicker accelerations, if you can call it that the way its driving.

Second: While at highway speed RPM's seem to be way above normal. At 60mph its spinning at 2500. If I take my foot off accelerator RPM's drop down to 1000, tap accelerator and it jumps back up to 2200-2500.

Third: From a stand still I have no power, floor it and it seems if were accelerating using the cruise control.

Don't feel any slipping, jerking. While it doesn't accelerate quick it still picks up speed. Didn't take it past 70mph, but even then it ran smooth just high RPM's.


I just recently bought this Tahoe and got it with code P1345. Even with this code it drove fine without the above issues. Ran fine, no power loss, no shifting issues, just the occasional buck.

Pulled codes today and it had P1886, trans control solenoid.

Read through a couple threads and replaced brake pedal switch and verified cruise control works. Would like to hear some opinions before I start tossing parts at it.


Cliffs:
2500rpms at 60mph, drops to 1000 if pedal released.
hard shifting 1-2
power loss at take off
P1886
no slipping, jerking, etc.
replaced brake pedal switch
checked fluid level
cruise control works

 

[SunlitComet]

p1345 is dizzy out of correlation alignment unrelated to solenoid which is causing you to not go into overdrive hence high rpms.


P1886

DTC P1886 3-2 SS Valve Assembly Electrical (1 Of 3)

DTC P1886 3-2 SS Valve Assembly Electrical (2 Of 3)

DTC P1886 3-2 SS Valve Assembly Electrical (3 Of 3)

3-2 SS Valve Assembly Circuit



CIRCUIT DESCRIPTION
The 3-2 Shift Solenoid Valve Assembly (3-2 SS Valve Assy.) is a normally-closed, 3-port, on/off device that controls the 3-2 downshift. The solenoid attaches to the control valve body within the transmission. The solenoid receives ignition voltage through circuit 1020. The Vehicle Control Module (VCM) controls the solenoid by providing a ground path on circuit 687. During a 3-2 downshift, the 2-4 band applies as the 3-4 clutch releases. The VCM varies the timing between the 3-4 clutch release and the 2-4 band apply depending on the vehicle speed and the throttle position.

When the VCM detects a continuous open or short to ground in the 3-2 SS Valve Assy. circuit or the 3-2 SS Valve Assy, then DTC P1886 sets. DTC P1886 is a type A DTC.

CONDITIONS FOR SETTING THE DTC

• The system voltage is 10-17 volts.
• The engine is running.
• All of the above conditions are met for 5 seconds, and either of the following fail conditions occurs for 5 seconds:
• The VCM commands the solenoid ON and the voltage remains high (B+).
• The VCM commands the solenoid OFF and the voltage remains low (0 volts).

ACTION TAKEN WHEN THE DTC SETS

• The VCM commands a soft landing to third gear.
• The VCM commands maximum line pressure.
• The VCM freezes shift adapts from being updated.
• The VCM inhibits TCC engagement.
• The VCM inhibits 4th gear if the transmission is in hot mode.
• The VCM illuminates the Malfunction Indicator Lamp (MIL).

CONDITIONS FOR CLEARING THE MIL/DTC

• The VCM turns OFF the MIL after three consecutive ignition cycles without a failure reported.
• A scan tool can clear the DTC from the VCM history. The VCM clears the DTC from the VCM history if the vehicle completes 40 warm-up cycles without a failure reported.
• The VCM cancels the DTC default actions when the fault no longer exists and the ignition is OFF long enough in order to power down the VCM.

DIAGNOSTIC AIDS

• Inspect the wiring for poor electrical connections at the VCM. Inspect the wiring for poor electrical connections at the transmission 20-way connector. Look for the following conditions:
• A bent terminal.
• A backed out terminal.
• A damaged terminal.
• Poor terminal tension.
• A chafed wire.
• A broken wire inside the insulation.
• When diagnosing for an intermittent short or open condition, massage the wiring harness while watching the test equipment for a change.

TEST DESCRIPTION
The item numbers below refer to the step numbers on the diagnostic chart.

4.This Step tests the ability of the VCM to control the solenoid.
5.This Step tests for voltage to the solenoid.
7. This Step tests the ability of the VCM and the wiring to control the ground circuit.
9. This Step measures the resistance of the Automatic Transmission Wiring Harness Assembly, and the 3-2 SS Valve Assy.

 

[RoRo]

pic attachments keep changing, could you please email them.


Just so I'm clear, p1345 has nothing to do with my shifting issues.
p1886 is either an electrical issue or bad part? troubleshooting external or internal?

 

[SunlitComet]

done.

---------- Post added at 04:34 AM ---------- Previous post was at 04:32 AM ----------

not related but still needs to be resolved.

yes.

read the document for the troubleshooting path.

 

[man n black]

Had a similar issue on my 05 at 120k. Turned out the tranny was bad. Shop owner said these trannies die at about 100k no matter what...

Good luck,
Ch

Sent from my DROID RAZR

 

[RoRo]

Where/which is the 20 way transmission connector? Is it attached to the pcm or trans itself? Need to know what plugs to pull to shoot some wires. All the connectors around the trans looked good.

Not really an update, but while the tahoe came up to temperature it drove normal. Shifted into OD and had power from a stop. But as soon as it got warm/hot went back to not shifting right and power loss.

 

[SunlitComet]

the connector on tranny. left side i think. By any chance you getting a "stored" P1870 code?

 

[RoRo]

the connector on tranny. left side i think. By any chance you getting a "stored" P1870 code?

ok, thanks.... I'll look for it.

at the time it had no other codes, just the 2.

 

[SunlitComet]

just checking for a common failure issue.

 

[reemo_2001]

SunlitComet Is there anyway I can get the pics sent to me as well? I know this post is old but i'm having the same problem, the truck shifts fine for the first 10 min of driving but after that it won't down shift to any other gear after coming to a complete stop. Throwing a P1886 code also. I can put it in 1st manually and pull off then put it in drive and the gears will shift up just fine.

I have a 96 Tahoe 4dr 2wd