4L60E no shift

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Mason Cramer

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pin E, a pink wire. could also be a fuse.
I replaced the ignition switch about a year ago with a high dollar one. Went down there to check again just to see. The connector still seems fine. All the connections seems sturdy. The pink ignition wire appears to be fine. Its not shorted or has any visible wear. From what i understand the pink wire would also be giving me issues with starting?? im not really experiencing that. All of my schematics do not show the ignition switch controlling any function of the transmission control.
 

Mason Cramer

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The VSS enables the transmission shifting, the speedometer, and the ABS--it's the "speed sensor" for the rear wheels.

On my '88, the signal from the VSS goes to the instrument cluster. The IC processes the VSS signal, sending it to the cruise control, ABS, speedometer, odometer, and the vehicle computer for use in computing fuel and spark needs. I don't know how much your '96 has in common with my '88.

Figure out:
1. Is the VSS sending a proper signal,
2. Where is the VSS sending the signal to? Instrument cluster? Vehicle computer? Body computer?
3. Is that component actually receiving that signal?
4. Does that component pass the signal elsewhere? Does the next component in the chain receive the signal?
I know that the Pre '96 trucks are much different electrically from the '96 and up due to OBD2. I own a 92 that has a much simpler system. Just for fun, i traced the VSS circuit and found that the 2 wires lead directly to the PCM pins 29,30 on the C1 Blue plug. I have continuity between the sensor wiring and the connection on the plug which would tell me that the wiring appears to be fine. I tested the new magnetic VSS and found that it works as it should.
 

thegawd

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pin e dosent do anything for starting. that's a different circuit. it does also power the oxygen sensor heater circuit as well. anyways this wire should read the exact same voltage as the battery. if it varies than it throws the tranny into limp mode. if there is anything electrically wrong with the 4l60e codes should be present but that might not be the case for a 92 and I dont know how limp mode would have behaved back then.... for obd2 vortecs, theres no prndl indicator light, your stuck in 3rd, theres no speedo and like 6 transmission codes.

Al
 

Mason Cramer

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pin e dosent do anything for starting. that's a different circuit. it does also power the oxygen sensor heater circuit as well. anyways this wire should read the exact same voltage as the battery. if it varies than it throws the tranny into limp mode. if there is anything electrically wrong with the 4l60e codes should be present but that might not be the case for a 92 and I dont know how limp mode would have worked then....
Right, i was also under the impression that "limp" mode was stuck in 3rd gear and i would presume throw codes. Im not getting a single ECM or TCM code. For that Pin E, should it have 12V while ignition on or is that an always hot 12V. And that would also be the same Pink ignition feed wire that goes to pin 4 on the C! Blue PCM connector??? If so, I get no power with ignition off and about 500mV less with the ignition on. Not sure of that voltage drop is just due to resistance though. Thank you though
 

Mason Cramer

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I have changed the TPS as well as the VSS with no change. Checked the harness, cannot find an issues. I'm getting 12V at the pink wire on the ignition feed to the 4L60E connector. When I unplug the connector, the transmission is stuck in actual "limp" mode where i only have 3rd gear in drive, and i can shift to 1st gear manually but no 2nd gear. The fact that i can shift through all gears and turn the TCC on and off through my scanner leads me to believe that the wiring harness is not at fault, as it would not send the signal to the PCM then to the tranny if it was broke somewhere. Is there something else that would stop it from shifting? The ABS light that comes on leads me to believe that an ABS wheel sensor is bad but I cant find any electrical diagram that shows how the wheel sensor could possibly tie into the TCM. Thanks
 

thegawd

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this is a case where pulling the tranny fuse just might get you home. wish I knew that when I blew my second tranny. I think I could have gotten home.

I agree that the harness is fine. so if you can command the truck to shift, does it actually shift? I'm not an expert by any means just learn from experience you know... to me it sounds like you have a mechanical problem inside.

Al
 
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