You are currently viewing our forum as a guest, which gives you limited access to view most discussions and access our other features. By joining our community, at no cost, you will have access to post topics, communicate privately with other members (PM), respond to polls, upload content and access many other special features. Registration is free, fast and simple, join LS1Tech.com today!
I really apologize if this question has been asked before but I have searched and not found the answer. I have a 97 Chev truck (4L60E) that I got the PO785 “Shift Solenoid Malfunction” error code last week. When warm it starts in 2nd or 3rd and will not shift into 4th and the converter will not lock. I went to the Chev house and they sold me two solenoids (identical) that think control the 1-2, 3-4 shift. They are located side by side at the front of the transmission. I replaced them and I have the same problem again and same error code. Note when it is cold everything works great. Only when it is warm does it not shift correctly.
Can anyone help? Did I replace the wrong solenoid?
PO785 Is a code for the 3-2 solenoid its located on the drivers side front. If this is the solenoid you replaced then you will need to start looking for electrical issues, Try unpluging the pluging back in the round plug over passengers side pan rail . Look at all wiring coming down from engine compartement .
Circuit Description with 4L60-E / 4L65-E Automatic Transmission
The 3-2 Shift Solenoid(SS) valve assembly 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 239. The Powertrain Control Module(PCM) 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 PCM 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 PCM detects a continuous open, short to ground or short to power in the 3-2 SS valve assembly circuit, then DTC P0785 sets. DTC P0785 is a type B DTC.
CONDITIONS FOR RUNNING THE DTC
The system voltage is 8-18 volts.
The engine speed is greater than 450 RPM for 5 seconds.
The engine is not in fuel cutoff.
CONDITIONS FOR SETTING THE DTC
DTC P0785 sets if one of the following conditions occurs for 5 seconds:
The PCM commands the solenoid ON and the voltage feedback remains high (B+).
The PCM commands the solenoid OFF and the voltage feedback remains low (0 volts).
do yall know what this is, ans what pin in the pcm, i may not have this hooked up right, bu8t keeps throwing the code, the only thing is have acutaly driven the car so dont know if the thing will even shift, i done all wireing my self,
PO785 ! ! !
Heres some helpful info dealing with the 4L60E Tranny and the PO785 Code. eRanch had the exact same problem I did, however, after I replaced the 5 solenoids,(PWM, LocK-up, 1-2 shift and the 2-3 shift,( these are identical solenoids) and the 3-2 Control Solenoid) plus the Pressure Manifold Switch, I still had the same problem. Ran fine when cold. Warmed up, and no Lo gear or 4th and over-drive. Only thing left to replace was the ECM.
It cost me $113.00 + 40.00 for programming, and problem is gone, and Tranny works just like it did when it was new.
If you have a 1997 Chevy or GMC and trouble with the Tranny and a PO785 code,
remember this info. It might save you a lot of time on your back looking at the underside of a 4L60E. I also put a drain plug on the pan to make fluid changes easier.
One more tid-bit of info.....the PWM solenoid is different from the 3-2 control solenoid but most suppliers list them as the same. The difference is the last letter of the part number.....Note: D74418e is the PWM solenoid....D74418EA is the 3-2 control solenoid.
The measured resistance on the D74418e is 5-15 ohms, on all the other solenoids the resistance is 20-25 ohms. Thats important to the computor's I/O.
I hope this info is helpful to others with the same problem, and eRanch may have trouble again with his 4L60E, so, just change the ECM.
Good luck everyone, and I hope I save you a tranny rebuild @ $2000.00.
My trans failed so I bought a 4L60E from similiar vehicle that had been T-boned and I had the trans shop install it for me, because I just had surgery. This owner of the wrecked vehicle had the trans rebuilt about a month before the accident.
After the install the trans wouldn't shift from first to second. The trans shop replaced the 1-2 shift solenoid. I drove it home, no issues. I drove it the next day and it slammed from 1-2 & 2-3 after it warmed up. I plugged in my Snappy scanner and I had no codes. I drove it today and it slammed when shifting again and turned the SES light on. I scanned it and I got codes P0785 - Shift Timing Solenoid "A" & P0894 - Transmission Component Slipping. I know the PCM commands maximum line pressure when P0785 is set, so should I assume its the solenoid and replace it?
Does anyone have schematics?
That is consistent with a bad 3-2 downshift solenoid. Keep in mind it could also be bad wiring inside the trans or a bad connection on the trans connector, but it usually is a bad solenoid.
This solenoid is located on the rear driver's side of the valve body, near the shift linkage. You only need a small flat screwdriver to pull out its clip to replace it.
i have a po785 error code on my 1998 Chevy Astro van. I dropped the pan and went to replace the 3-2 solenoid and found that it has 2 very similar looking 3-2 shift solenoids....they look identical except one has a grey connection cap and the other has a red connection cap. These solenoids are different thean the square 1-2 2-3 shift solenoids. Any help?