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4L60E IN LIMP MODE

 
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Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/14/09
07:08 PM

1994 K1500 5.7L TBI
My trans. is in limp mode. Here is what I have checked and changed so far with no fix. I have change the 1-2 solenoid 2-3 solenoid 3-2 down shift solenoid.  I have check for continuity and for short to ground in the transmission and the wire harness from the trans to the ECM.  I have checked for shorts between all circuts in the wire harness going to the transmission. I have changed fluid and filter several times. All of this has done no good.  I am getting a DTC 66, 3-2 down shift circut fault.  Oh yeah I also have checked power at the trans fuse and at the trans harness connection.  SO WHERE DO I GO FROM HERE?  

waynep712 waynep712
Enthusiast | Posts: 652 | Joined: 10/08
Posted: 05/15/09
06:59 AM

just curious........     did you disconnect the battery or pull the proper ecm fuse to clear the codes?????   they don't reset on their own... it may take a scan tool to reset the codes on that pcm....  other wise it may/ will stay in limp in home mode..

do you have the old solenoids??????    did you ohm them after or before you took them out..?????   were any of them shorted... less than 20 ohms?????  it might have burned out the pcm circuit...

there is a mode you can get to with a scan tool... where you can turn on all the solenoids with the key on engine off.. to verify the pcm is pulling that circuit to ground... its quicker to buy a old internal transmission harness and build that up for testing when you have this kind of problem.. just be sure that every wire cannot short to anything else...
are the pins inserted all the way in the transmission connnector?????  not pushed back .????  both sides...


oh... and what do the rest of the sensors voltages look like....  throttle position sensor, coolant temp,  does that have throttle pedal angle switches on the gas pedal inside the cab????  

jgate-#002 jgate-#002
Guru | Posts: 953 | Joined: 06/07
Posted: 05/15/09
09:24 AM

The Power Relay System was designed to eliminate DTC 66, 67, 81, 82, and 83 on 1994-up GM trucks. These codes are many times set because the ignition switch fails to supply enough voltage to the Transmissions ignition circuit, just after start up. Once the ignition switch fails to provide adequate voltage to the solenoids, the feedback to the computer trips any combination or all of the codes above. You can replace the ignition switch, as a possible temporary fix, or install the Power Relay System and FIX the problem. The advantages of installing the Power Relay System are: It will make the ignition system more reliable.
It is much faster than replacing the ignition switch.
It is far less expensive than replacing the ignition switch.
Any transmission shop could easily install the Power Relay System, where as the ignition switch replacement, usually falls in the general repair field.

Installing the relay is very simple. All the wires are clearly tagged. The relay installs under the hood at the fuse-relay box on the drivers side. All you do is connect the GROUND to the master cylinder. Then connect a 12 VOLT supply,that is easily found behind the fuse-relay box. Next you tap into the main IGNITION circuit inside the fuse-relay box.This fuse is easy to find, as it is the front most outside ignition fuse. The last wire you splice into the transmissions case connector's "E" terminal. Mount the relay and you are finished. It takes about 20 minutes to install.  
NO power to the shift solenoids would put the trans in limp mode , 3rd gear only.  

Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/15/09
03:43 PM

thank you for the info on the relay system sounds great.  Please tell me if I am missing something, but I have checked power at the trans fuse and at the trans connector term. E both have power, however I have only checked this with the key in the run position with the engine NOT running, batt voltage only.  Is this the correct check or is there a way to check with the truck running?  If I unplug the trans. connection and start the truck the pcm will set all kinds of code. will that cause a problem with checking the voltage at term. E?  

Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/15/09
03:48 PM

I did clear the codes. I do have the old sodenoids. I did ohm the new ones after install, none are shorted, yes some are less than 20 ohms, but they are all in spec per ATSG manual.  All the pins on both connectors look good and are solid. I have not checked any voltages at the TPS, Coolant temp and no it does not have throttle pedal angle it has a pressure control solenoid.  

Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/15/09
03:52 PM

I just cleared codes again today and ran the truck.  The code I have now are  66 3-2 control solenoid circuit fault, DTC 73 Pressure control solenoid Current, and DTC 81 2-3 shift solenoid circuit fault.  3-2 and 2-3 solenoids are new parts. I have not changed the pressure control solenoid, but when I ohm this circut from the ECU connector the reading is 4.4 ohms the range is 3.5 to 4.6  

jgate-#002 jgate-#002
Guru | Posts: 953 | Joined: 06/07
Posted: 05/15/09
06:14 PM

These codes are set because the ignition switch fails to supply enough voltage to the Transmissions ignition circuit, JUST AFTER start up. Once the ignition switch fails to provide adequate voltage to the solenoids, the feedback to the computer trips any combination or all of the codes.
I would say that your problem is with the ignition switch.

another problem these trucks had.....

Beginning at the start of production for all 1994 model vehicles equipped with the THM 4L60-E transmission, there was a VCM (Vehicle Control Module) installed on the vehicles with an internal ground wire that connects the two printed circuit boards together. Some vehicles with the VCM will display very erratic and unstable line pressure rise in the transmission, and in some instances, premature failure of the transmission. Bad ground connection from one printed circuit board to the other.
There is now available from OEM parts sources, a new service repair kit with an instruction and is available under OEM part number 12167310.  

Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/15/09
07:59 PM

Thanks again.  I am going to look into the ignition relay setup.  Is this a kit that can be purchased? do you have any P/N.  Or is this something you put together with misc. parts?  My truck does not have the vcm you are talking about here, I have a ECM located behind the glove box.  I found out that the bad ground wire deal is on this S/B #00-07-30-026 - (12/21/2000) Automatic Transmission 1-2 and/or 2-3 Upshift Slip/Flare, No 3rd or 4th gear, Launch Shudder (Revise VCM Wiring)
1996 Chevrolet and GMC C/K, S/T, M/L, G1, G2, P3 Models
1996 Oldsmobile Bravada
with VCM and 4L60-E (M30) or 4L80-E (MT1) Automatic Transmission  

Boyd1 Boyd1
New User | Posts: 6 | Joined: 05/09
Posted: 05/16/09
09:23 PM

Just wanted to let you know I got it fixed today.  Bad  pressure control solenoid Although the solenoid had proper ohm reading, the valve was not operating correctly due to wear on the internal piston. Which caused max line pressure, which set code 73 which put trans in limp and set DTC 66 and DTC 81.  Thanks for your response. Smile  

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