Code 452
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
He has hard shifts so we know the pressure is higher than normal.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
Yes the speed control module has been known to cause this also as it can cause the signal from the PSOM to the PCM to be bad.
Just unplug it for a test.
Just unplug it for a test.
Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,750
From: Kentucky
Thread Starter
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Freshman User
Joined: Feb 2020
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What and where is the speed control module? I am not familiar with that. Also I tried to pull the RABS codes before and none came up, and I have plenty of fluid.
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Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,750
From: Kentucky
Speed Control is Ford's version of Cruise Control which is a GM term.
I believe your 1992 MY trucks uses the older RABS-I system.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
Likes: 301
From: Easton,Ks
If it does not work unplug it anyway.
It is called a Amplifier in the diagram below.
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Fleet Owner
Joined: Oct 2005
Posts: 20,783
Likes: 1,750
From: Kentucky
I caught the RABS-I based on your 1992 MY, but did overlook your truck also uses the older style vacuum-servo speed control system. Looks like Bill has the updated info for you.
Frmr Ford Trans Engr
Joined: Aug 1999
Posts: 24,696
Likes: 2,618
From: SE Florida
The MLP cannot set a code 452. That code is what is causing this problem.
Ford NEVER made MERCON fluid. Ford licensed others to make MERCON fluid. Ford discontinued licensing MERCON is 2006, so NOBODY has made MERCON since 2006. You can still find fluid labeled DEX/MERC, but it isn't MERCON. It may or may not meet MERCON specs. The correct fluid now is MERCON V.
You might as well jack up the front end and check the wheel bearings. Just like the transmission, they also CANNOT cause a code 452, which is your problem. Checking the trans pressures is a fun exercise, but it will NOT help you find out what's wrong. The code 452 is your entire issue. When that code is set the transmission line pressure is set high. The harsh shifts prove this. Checking your pressures with a gauge will confirm this, but won't help fix anything.
This is a list of what is causing your problem. Anything else may be fun to do, but one or more of these four things are causing the code 452, which causes the trans pressure to be high and makes for harsh shifts. If you are checking anything but these you are not working towards fixing the problem.
Apparently i am failing to understand this issue. Are we not checking to see if transmission is sound. Regardless of code 452, we need to know this. This test is not related to anything electronic. Valve switching is all manual. If transmission is faulty, nothing will fix it, especially a seperate controller.
This is a list of what is causing your problem. Anything else may be fun to do, but one or more of these four things are causing the code 452, which causes the trans pressure to be high and makes for harsh shifts. If you are checking anything but these you are not working towards fixing the problem.
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Freshman User
Joined: Feb 2020
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I unplugged the speed control sensor. No change. It had 2 plugs going into it. I matched up the color codes for the wiring and pulled that plug first, test drove and then pulled the other plug and test drove. No change on either, I plugged them back up. Just to be sure here, each step I try would produce an instant change correct? Meaning I wouldn’t have to drive for so many miles or drive cycles or have to unhook the battery or clear codes between each step, right? Since this truck has a new PSOM and new PCM I can look towards the ABS sensor or wiring, correct? If I unplug the ABS sensor(which is along the inside of the frame rail under the driver’s feet right?) would that be sufficient or is there an operational test for it? I have gone over the wiring harness on this thing in these areas a few times now. I have not seen one even questionable area. The whole harness seems to be tucked away in the plastic sheath and for the most part all taped up. I can find no signs of rubbing or wear and tear.
Fleet Owner
Joined: Aug 2005
Posts: 23,666
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From: Easton,Ks
The ABS/DSS/VSS are just different names for the same rear end sensor. The harness for the sensor does run down the drivers side frame rail.
Not sure where you saying to unplug it but the resistance value of the sensor should be about 1400 ohms.
Not sure where you saying to unplug it but the resistance value of the sensor should be about 1400 ohms.