4l60e no 1st or 4th
4l60e no 1st or 4th I have a 06 Silverado with 4l60e. No 1st or 4th gear. Starts in 2nd and shifts to 3rd fine. Solenoids are good, harness is good. And there is continuity all the way to the PCM. I don't believe the PCM is pulling the solenoid to ground. I don't have a scanner to trigger the noids but tried another PCM and the problem still exists. anyone have any ideas or suggestions. I don't know where else to look at this point.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
The only thing 1st and 4th have in common is Solenoid A - it is stuck in the OFF position. What makes you say "solenoids are fine"?
Take the car to a trans shop and have them hookup a scanner to it.
Solenoids have a very fine filter on them. If it gets clogged, they act like OFF.
Take the car to a trans shop and have them hookup a scanner to it.
Solenoids have a very fine filter on them. If it gets clogged, they act like OFF.
Ive tested them both. solenoid a is not pulling to ground. I had it to 2 shops already 2 different answers. Trans shop tried to sell me a rebuild other shop tried to pin point the valve body. i have the pan off now. With the key on both noids should be activated. Not the case only the 2-3. Power is just passing through the 1-4. i can ground it myself and activate it.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
Well, you sure don't need a rebuild. Wow, no wonder trans shops have such a bad reputation.
So, you are absolutely sure of the electrical continuity to the PCM and you have even swapped the PCM.
What is the voltage on Solenoid A with the ignition on?
I am try to determine if the PCM is partially grounding it.
I.e. if the voltage drops to e.g. 6 volts, the PCM is trying, but not enough. I would then look for a broken wire in the harness. It might show continuity with the Ohm meter, but not be able to handle the 1 amp needed for the solenoid.
Next I would use a scanner to see if I can force 1st and 4th gear.
Probably far fetched, but I wonder if the Pressure Switch manifold is indicating the wrong shifter position to PCM. E.g. first indicating [D2] which start in 2nd gear and then indicating [D3]. Probably not even possible, but when this part is defective, you get very strange symptoms.
So, you are absolutely sure of the electrical continuity to the PCM and you have even swapped the PCM.
What is the voltage on Solenoid A with the ignition on?
I am try to determine if the PCM is partially grounding it.
I.e. if the voltage drops to e.g. 6 volts, the PCM is trying, but not enough. I would then look for a broken wire in the harness. It might show continuity with the Ohm meter, but not be able to handle the 1 amp needed for the solenoid.
Next I would use a scanner to see if I can force 1st and 4th gear.
Probably far fetched, but I wonder if the Pressure Switch manifold is indicating the wrong shifter position to PCM. E.g. first indicating [D2] which start in 2nd gear and then indicating [D3]. Probably not even possible, but when this part is defective, you get very strange symptoms.
I'll check the voltages on both. It's definitely confusing I've been racking my brain trying to get it straight. I had the same thoughts about the pressure manifold switch so I ruled it out with a new one from GM. I was going to buy hp tuners to for the scanner features to help diagnose this and for later use on my car. But I got busy with work so I decided to pay a shop to fix it which didn't work out as you know.
Moderator
Joined: Aug 2010
Posts: 7,323
Likes: 529
From: Ann Arbor, MI
What city are you in?
Besides the sponsors, many of the participants here own/work-in auto/trans shops and might be able to help you. Any decent and honest trans shop will start by connecting a scanner, putting the wheels up and testing which gears can be commanded and which will select automatically.
Since you already know a lot about about transmissions, you might want to get a copy of GM's official "Hydramatic 4L60E Technicians Guide" which has diagrams and explanations of all the hydraulic circuits and parts. If by chance you have a stuck valve in the VB, this would help you figure it out.
Besides the sponsors, many of the participants here own/work-in auto/trans shops and might be able to help you. Any decent and honest trans shop will start by connecting a scanner, putting the wheels up and testing which gears can be commanded and which will select automatically.
Since you already know a lot about about transmissions, you might want to get a copy of GM's official "Hydramatic 4L60E Technicians Guide" which has diagrams and explanations of all the hydraulic circuits and parts. If by chance you have a stuck valve in the VB, this would help you figure it out.
TECH Junkie
Joined: May 2012
Posts: 3,050
Likes: 716
From: Poplarville, MS
Is the PCM commanding the A Solenoid on? If it’s not commanding A Solenoid on, most likely you have a sensor problem. My first guess would be the Pressure Switch Manifold, but I see you have changed that. I have gotten new defective parts before but the odds of the new part having the same defect I think would be slim. You’re really are going to need a scanner for this one.
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Yeah I really should have just bought one from the beginning instead paying for a diagnosis that I felt was inaccurate. Twice! I'm not sure what other sensor could cause this. I've cycled the gear position switch with no changes and it reads correctly on the cluster. I appreciate your guys suggestions because I'm out of ideas.
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