4L60E stuck in LIMP MODE
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Teching In
Joined: Nov 2017
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4L60E stuck in LIMP MODE I have a 4L60E transmission in a 1998 K1500 Pickup. The problem is that I can not get it out of limp mode. I am pulling a P0758 code (Shift solenoid B electrical. I have replaced Vehicle Speed Sensor, ignition harness, Throttle Position Sensor, Neutral Safety Switch, and Shift solenoids A & B. Tonight I was testing power and found that I only had 4.5 VDC @ transmission pin E, while at it's origin, Fuse 20 inside fuse block, I have 13.6. Also, I do not have any voltage on Pin C which should have 12 volts. Pin L has 13.6 as well. I have been chasing a cure for 2 weeks now off and on but come up empty handed.... Any advice for me?
Thread Starter
Teching In
Joined: Nov 2017
Posts: 4
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**** UPDATE**** I created a harness that allows me to plug in a test connector inline while it plugged into the transmission and vehicle harness. As I was checking transmission harness for real time voltages, I found terminal "E" which is supposed to have 12 volts, only had 4.6 volts. Terminals "A" & "B" had 12 volts even though they are switched grounds. I looked into the PCM and decided to change it based on electrical schematics I had found, and there were too many voltage values incorrect. I went to LKQ (Junk yard) and purchased a PCM from a 1999 K1500 Suburban ($36.80). Installed the PCM and truck would not stay running because of security system. Reset security system by bumping starter, leaving key on for 10 minutes, turning key off for 10 seconds, and repeating this step two more times. Truck started and showed no codes. Took it for a test drive, 1st, 2nd, 3rd, 4th and stayed in 4th without posting any codes. I took the truck to work, 60 mile round trip and had no issues. So my problem was the PCM the entire time. One thing I did know, the transmission was 3 years old and had only 1000 miles on it at the most. With this being said, that is what made me look into the electronic circuitry vs. transmission problems.
